eHam

eHam Forums => Amplifiers => Topic started by: AH7I on July 06, 2019, 07:15:18 AM



Title: Goodbye tubes.
Post by: AH7I on July 06, 2019, 07:15:18 AM
NXP has 300W 50V with 28 dB gain for $35/each (Mouser) and $25/each in qty suitable to a small manufacturer. https://www.mouser.com/datasheet/2/302/MRF300AN-1381586.pdf
Four of these make 1200W output HF amp.
It looks very attractive for single band/amp per antenna application that is competitive with anything having a tube.




Title: RE: Goodbye tubes.
Post by: K6AER on July 06, 2019, 08:16:36 AM
Stated wattage of a transistor is its maximum dissipation. The transistor will not last long at maximum wattage. You will find that in order to have a good IMD level these devices generally have to be run at 70% of maximum wattage. A solid-state amplifier with enough head room for a 1500-watt output and good IMD numbers (-35dB two tone) will cost almost twice that of an equivalent tube amplifier.


Title: RE: Goodbye tubes.
Post by: DL8OV on July 06, 2019, 09:45:01 AM
Read the datasheet carefully, the output figure you see may be for pulse operation.

Having said that, a pair of these ran at 45V and generating 100W would be a nice clean P.A. providing you got the output transformer right.

Peter DL8OV


Title: RE: Goodbye tubes.
Post by: AC2RY on July 06, 2019, 11:48:05 AM
Read the datasheet carefully, the output figure you see may be for pulse operation.

Having said that, a pair of these ran at 45V and generating 100W would be a nice clean P.A. providing you got the output transformer right.

Peter DL8OV

This device won't be very efficient in real life operation. Miller capacitance shoots up below 20 volts D-S. Thus for wide band stability, you need to keep drain voltage above that. Which means significant loss of efficiency. Just compare it with BLF188XR in which capacitance jumps up below 5 volts D-S, thus allowing for more useful drain voltage range. When you design amplifier for a single frequency you can compensate  that capacity, but this is not possible when you need to cover the whole range between 1.8 and 55 MHz.



Title: RE: Goodbye tubes.
Post by: N8FVJ on July 07, 2019, 05:32:30 AM
IMO tubes have been obsolete for years with the exception of high power tube amplifiers. Tubes easily tune into a 2 to 1 SWR whereas solid-state cannot tolerate more than 1.5 to 1 SWR. I use the MyAntennas EFHW8010 antenna that has a 2 to 1 SWR on 75 meters and about 1.5 to 1 on 40 to 10 meters. You need an amp on 75 meters at night anyways. No expensive high power antenna tuner required.

Now, I read some solid-state amps have a built-in tuner, but very expensive. Only new tube left that lasts 10 years or longer is the Chinese 3-500Z. You can buy NOS Cetron 572B that are known to last 20+ years, but expensive and rare.


Title: RE: Goodbye tubes.
Post by: AC2RY on July 07, 2019, 08:29:38 AM

Now, I read some solid-state amps have a built-in tuner, but very expensive.

Everything is relative. Good mid-range transceiver is around $3000. Good 500-600W solid state amplifier WITH tuner can be purchased for similar amount of money.

Things get more expensive when you go over 1000W, but then everything in your transmission chain allowing effective use of that power becomes expensive. Just like high-end transceivers go up in price to $10K and above.


Title: RE: Goodbye tubes.
Post by: K6AER on July 07, 2019, 10:09:51 AM
IMO tubes have been obsolete for years with the exception of high power tube amplifiers. Tubes easily tune into a 2 to 1 SWR whereas solid-state cannot tolerate more than 1.5 to 1 SWR. I use the MyAntennas EFHW8010 antenna that has a 2 to 1 SWR on 75 meters and about 1.5 to 1 on 40 to 10 meters. You need an amp on 75 meters at night anyways. No expensive high power antenna tuner required.

Now, I read some solid-state amps have a built-in tuner, but very expensive. Only new tube left that lasts 10 years or longer is the Chinese 3-500Z. You can buy NOS Cetron 572B that are known to last 20+ years, but expensive and rare.

The Chinese FU728F Tetrode is rated for 1800 watts continuously and only cost about $400. Gain is about 15-16 dB depending on screen current. I have seen these tubes put out easily 2.3 KW in SSB mode with 60 watts drive. This tube was modeled after the 4CX1500B.


Title: RE: Goodbye tubes.
Post by: WB8VLC on July 08, 2019, 01:23:31 PM
The  Motorola/Freescale/NXP group (sorry to the NXP guys but I'm ex Moto from the 1st days of LDMOS  development so it's still Moto to me)  down in Tempe already have these operating I believe across HF/6 meters and they were heard during field day  on 6 meters using a P-P MRF300 A/B amp at around 600 watts on FT8.

Also the NXP guys discovered that with the MRF300's and the newer LDMOS 65 volt parts that running them off of 50  or 65 volts and not backed off in Po actually resulted in the best overall efficiency which wasn't the case with the P-P MRFE6VP5300 amp that I made. nor with a similar single BLF184 amp.

I'm using 2 X $69 dollar 15 amp mean-well 48 volt  supplies (because I'm cheap) on my Mouser bought MRF300A/b P-P parts from 14 to 54 MHz with good results,  14 to 54 Meg are the only bands which I presently have antennas for at this time.

So far the 300A/B's are more rugged than the 2x MRFE6VP5300 P-P amp (500 watts out) that I made 3 years ago similar to Lionel Montgin's fine design of several years ago and the 300 A/B is on par with a BLF184 single amp that I made although the BLF184 is more suitable for ~650 watts whereas the 300A/B P-P amp is best around 575 watts max in my case.

So far using mine under extended FT8 mode on 20 somewhat  and many hours  on 10 and 6 meters CW/SSB /FT8 and even 50.3 and 29.6 FM, even for one 3 hour US to JA opening on 6 meters FT8 the 300 A/B P-P amp has worked just fine.

As mentioned I also use it on 50.3 FM  and 29.6 FM and my nearest neighbor W7EW, 1 1/2 miles from me, even with his massive array of antennas pointed at me, hasn't had any issues when we operate within 15 KHz of each other  he on 50.313 and me on 50.3 and even when we are operating different sequences on the 50.313 so he hears me there haven't been any issues.

The NXP guys in Az  also have a design challenge running thru I believe Arrow for a home brew challenge for builders using the MRF100 A/B 100 watt and the MRF300 A/B 300 watt devices.

There are already a couple of russian guys who are working on commercial amps using the 300 A/b's and one may already have one on the air using the MRF300's  on HF/6 meters.

As long as 50 Vdd and a 3 db over drive are not exceeded they seem to be very rugged parts and at around 40 dollars even if I kill one the pain is minimal compared to the MRFE6VP5300 P-p and a BLF184 which are considerably more expensive and I have already killed some.

My success at not killing anymore of my LDMOS devices may because I'm now using an input overdrive Pin limiter circuit similar to ON7EQ's fine design to keep from hitting above a 1 db or whatever I set it at over-drive level and so far no dead 300 A/B's.

In the very early days of LDMOS during the development of the  2nd gen parts in the late 1990's at Moto in Phoenix I was know for killing more LDMOS devices than cockroaches in Phoenix's Arcadia neighborhood where our plant was located.

On the other end of the extreme my company just bought 2  new, 1-2 GHz/4 KW Solid State  amps for use in  reverb chamber and these amps also are based on several combined NXP parts and presently being used in our EMC lab.

Although being a commercial lab grade EMC amp they are considerably more expensive than my home brew amp, still these newer LDMOS devices are very nice.


Title: RE: Goodbye tubes.
Post by: AH7I on July 09, 2019, 07:21:58 AM

...

So far the 300A/B's are more rugged than the 2x MRFE6VP5300 P-P amp (500 watts out) that I made 3 years ago similar to Lionel Montgin's fine design of several years ago and the 300 A/B is on par with a BLF184 single amp that I made although the BLF184 is more suitable for ~650 watts whereas the 300A/B P-P amp is best around 575 watts max in my case.

...


Thank you for commenting and references. I am interested in constructing a pair of amplifiers to drive phased 40/80 verticals with the phasing done on the input side. I was looking at a pair of SD2933 per each but these Motorola parts are considerably less expensive.

73, -Bob ah7i


Title: RE: Goodbye tubes.
Post by: WB8VLC on July 09, 2019, 11:53:26 AM
Mine is far from complete right now from what I would eventually like to have which would be an auto switched LPF/swr detector design that one day is controlled by my main HF/6meter rig.

 Right now I have  individual coax cabled in low pass filters for the main 3 bands that I use only because I didn't have the extra time nor the extra money to spend to roll a multi-relay or multi-Pin diode switched low pass filter board which would be in the hundreds of dollars.

Possibly, some day I'll sit at the PC and roll a relay or Pin switched LPF board in PCB-Express but only if I have the free time and spare money to spend other wise it will be a hillbilly design using cabled in one at a time LPfilter boards for the band that's being used at any particular time. 

DC switching for Vdd and Vgg were cheap but very good designed W6PQL boards along with a W6PQL 4 event sequencer that does input/output switching and Vdd/Vgg switching at the proper times.

The various boards available from W6PQL let me get the amp on the air quickly.

Also everything is pretty much open frame design on a large freescale provided copper heat-spreader/ bare board with attached 5 inch long beautifully milled aluminum finned heatsink, this is a real Freescale provided A1 heatsink design that lets me operate without a fan.

In typical cheap-ham-dot-com fashion, which I rigorously adhere to, I used anything from my junk box or anything that I had donated to keep cost down.

I have everything crammed in an old Palomar CB amp case that was donated by a ham friend so overall looks-wise it's not very pretty but at least it's clean RF wise and lets me operate with considerably more than my exciter power.





Title: RE: Goodbye tubes.
Post by: OZ8AGB on July 11, 2019, 01:31:52 AM
Goodbye tubes??

Oh.. I just bought an ACOM 1010 tube amp...


Title: RE: Goodbye tubes.
Post by: M0HCN on July 11, 2019, 07:16:22 AM
As ever be a little careful with front of datasheet ratings, especially with TO series plastic packages as getting heat out can be a pain.

I would consider a pair of those to make a decent 300W or so stage while allowing the heatsink to run at a reasonable temperature, 600W in AB from those packages would have me really nervous (It could certainly be done, but solder mounting and some very careful figuring of Tj would I think be required to make a reliable design).

TBH, at this point I take the view that the cost of the power sand is low enough compared to the incidentals that running it balls out is generally a poor design decision (Really it always was), much better to over spec the power devices and save on the heatsinks, most of your cost is not in the power transistors anyway (LPF bank, power supplies, case, cooling, matching will generally cost more then the power devices). It used to be the case that the power semiconductors were the elephant in the room, but I would argue that this has not been true since the modern LDMOS stuff hit the streets.

 
73 Dan.


Title: RE: Goodbye tubes.
Post by: G3RZP on July 11, 2019, 02:33:39 PM
So just how good are the power LDMOS in terms of high order IMD? The last generation of tube PA gear had relatively little 7th order IMD and negligible 9th order and higher....

A friend of mine who works on designing microwave PAs with LDMOS thinks they are pretty bad from his experience....


Title: RE: Goodbye tubes.
Post by: AH7I on July 12, 2019, 04:06:55 AM
So just how good are the power LDMOS in terms of high order IMD? The last generation of tube PA gear had relatively little 7th order IMD and negligible 9th order and higher....

A friend of mine who works on designing microwave PAs with LDMOS thinks they are pretty bad from his experience....


HF IMD is good enough to meet code. My application, CW, is much less a concern. LID is by far(orders of magnitude) the greatest contributor to crap on HF.

73, -Bob ah7i/w4


Title: RE: Goodbye tubes.
Post by: AH7I on July 12, 2019, 04:15:29 AM
As ever be a little careful with front of datasheet ratings, especially with TO series plastic packages as getting heat out can be a pain.

I would consider a pair of those to make a decent 300W or so stage while allowing the heatsink to run at a reasonable temperature, 600W in AB from those packages would have me really nervous (It could certainly be done, but solder mounting and some very careful figuring of Tj would I think be required to make a reliable design).

TBH, at this point I take the view that the cost of the power sand is low enough compared to the incidentals that running it balls out is generally a poor design decision (Really it always was), much better to over spec the power devices and save on the heatsinks, most of your cost is not in the power transistors anyway (LPF bank, power supplies, case, cooling, matching will generally cost more then the power devices). It used to be the case that the power semiconductors were the elephant in the room, but I would argue that this has not been true since the modern LDMOS stuff hit the streets.

 
73 Dan.


Thanks. My application is one or two bands and morse. I expect a pair of 300W/each continuous rated devices running at morse duty cycle to have plenty of thermal overhead when reasonable consideration has been given to heat transfer.





Title: RE: Goodbye tubes.
Post by: M0HCN on July 12, 2019, 04:29:52 AM
G3RZP, I know you know this, but for others, a big part of the IMD issue is that pretty much everyone runs the damn things with a swamped gate (Transformer down to a few ohms, then swamp the gate capacitance with a low value resistor).

It is easy, stable, very high gain and rather less prone to gate overdrive issues then a feedback amplifier is. You get a 36dB gain stage, taking maybe a couple of watts to get your kW, and burning power in an input attenuator to reduce the 100W from the rig to something the gates will survive. Problem is, it is pretty damn close to being open loop!

If instead you burn that 100W of drive power in the feedback resistors and wind up with say 13dB of stage gain, you have substantial feedback around the device and thus very much better IMD levels. Feedback always makes the products more complex, so you need to use enough of it, but it does substantially linearise the stage.  

The problem with a high feedback design is that the thing becomes very sensitive to overdrive because once the FET drains are banging into hard saturation, the feedback goes away and gate voltages shoot up, the same thing happens if you have a shorted output for example where there is NO RF voltage at the drains irrespective of the gate voltage (In a open loop design the PSU current trip comes to the rescue, but that does not help here or prevent the gate being blown out).

You MUST provide gate overdrive protection if doing this (PIN switch or similar and clamps), and it must sense the gate voltage, not the input power, because in the event of a load problem the two are not the same.

You should also do the load pull studies and plot the stability circles, as stability can be rather more of an issue.

On the bench I can hit -60dBc (Not PEP) IMD3 with the higher order products off my SA screen by 9th (So better then about -90dBc), turning that into a publishable design is of course the 'ask me for anything but time' activity.  


73 Dan.


Title: RE: Goodbye tubes.
Post by: G3RZP on July 12, 2019, 10:21:22 AM
Dan

Quote
The problem with a high feedback design is that the thing becomes very sensitive to overdrive because once the FET drains are banging into hard saturation, the feedback goes away and gate voltages shoot up, the same thing happens if you have a shorted output for example where there is NO RF voltage at the drains irrespective of the gate voltage

That was basically known many years ago (more than I've been alive!) and has since often been forgotten!! (Does any university teach analogue and RF design anymore?) See ‘Second thoughts on radio theory’ by ‘Cathode Ray’, published for Wireless World, Iliffe & Sons Ltd., London, 1955, or in Wireless World, ‘Negative Feedback’ by ‘Cathode Ray’, February & March 1946, (available at https://www.americanradiohistory.com/)

The other 'little' thing with a high feedback design is ensuring that the Nyquist plot stays stable at all power levels - and it is of course dependent on things like Miller capacity (variable with signal level!) and gain compression. (Personally, I always prefer a Bode plot, because it doesn't need normalising). And of course, stays stable with the impedance circles that it sees at the harmonic frequencies, which can be a different kettle of fish....

It is somewhat frightening to see the extent to which - especially the higher order - IMD Products have got worse over the years since tube PAs  stopped being made....




Title: RE: Goodbye tubes.
Post by: K4EMF on July 12, 2019, 10:54:17 AM
I have to say I find reading you guys that know electronics very interesting.  Even if I don't always know exactly what you're talking about.


Title: RE: Goodbye tubes.
Post by: M0HCN on July 12, 2019, 10:57:39 AM
Yep, fairly basic feedback system theory.

Harmonic stability can also be a case of making sure the exciter terminates harmonic power coming back down the link cable reasonably (Most don't), which is one of those things that makes me feel that building a transmitter usually trumps building an amplifier, much easier to the the transmitter case right when you control the whole damn chain, and it is not like small signal doings are notably expensive these days. The upside of dumping 90% of the exciter power into a pad is that a 10dB pad at least guarantees a 20dB return loss for the harmonics heading towards the rig, directly connecting puts the output part of the LPF across the gate network (phase rotated by the length of cable), this is not good.

Fortunately these days we have software that does harmonic balance and load pull calculations and that can plot the stability circles for us.....

It is not that LDMOS is bad, its just that there seem to be the same old tired designs based on prehistoric Motorola app notes from when the MRF150 was young that keep on being minimally respun for new devices (Except that some of those old app notes actually had feedback!).

Cathode Ray was awesome!

73 Dan.


Title: RE: Goodbye tubes.
Post by: G3RZP on July 12, 2019, 03:11:01 PM
Dan,

Back in about 1975, there was an article in 'Electronics' magazine about predicting stability in solid state PA with the impedance circles of the load impedance at the harmonic frequencies on Smith Charts....I figured back then that design of valve amplifiers was easier - although at the time, I was leading a group on HF receiver design...which (story of my life) had a reorg and never got into production afterwards...

Yes, a lot of 'Cathode Ray'(M. G. Scroggie) is still good basic knowledge today...


Title: RE: Goodbye tubes.
Post by: M0HCN on July 12, 2019, 03:59:02 PM
The problem with stability circles on a Smith chart is that it can be tricky to tell which side of the curve is the stable one...

The basics don't change and a newbie could still do worse then reading F.Termans magnum opus (Also, Langford-Smith).

73, Dan.


Title: RE: Goodbye tubes.
Post by: G3RZP on July 13, 2019, 05:57:36 AM
Scroggie's  (Cathode Ray) 'Essays in Electronics' has a good introduction to Nyquist diagrams that is far, far better than I had at college!


Title: RE: Goodbye tubes.
Post by: NO9E on July 13, 2019, 07:28:41 AM
With new transistors, the old concept of transceivers is probably obsolete. The original concept was useful to avoid replication and ensure same frequency without many cables. The new transmitter can use a digital stream or generate all modes natively, has ALC and pre-correction internally,  adjust PS voltage for optimal efficiency, etc. And the receiver is either connected via Ethernet or is a small board inside. With higher efficiency, probably what made 100W before can now make 300W with same weight and heat.

The current FCC rules limit the amp gain to 15 db. But it does not apply to a digital input.

An intermediate new design of that sort could be Expert 1.5k with kx3 fitted inside and KX3 software adapted for pre-correction etc.
21 lb 1.5 KW and low IMD. Zenki special.

Ignacy, NO9E
 


Title: RE: Goodbye tubes.
Post by: W9IQ on July 13, 2019, 03:47:17 PM
Quote
The current FCC rules limit the amp gain to 15 db. But it does not apply to a digital input.

How is it that the 15 dB limit does not apply to digital? The regulations don't seem to grant such an exemption:

Quote
Not be capable of amplifying the input RF power (driving signal) by more than 15 dB gain. Gain is defined as the ratio of the input RF power to the output RF power of the amplifier where both power measurements are expressed in peak envelope power or mean power. 


- Glenn W9IQ


Title: RE: Goodbye tubes.
Post by: AC2RY on July 13, 2019, 05:39:02 PM
Quote
The current FCC rules limit the amp gain to 15 db. But it does not apply to a digital input.

How is it that the 15 dB limit does not apply to digital? The regulations don't seem to grant such an exemption:

Quote
Not be capable of amplifying the input RF power (driving signal) by more than 15 dB gain. Gain is defined as the ratio of the input RF power to the output RF power of the amplifier where both power measurements are expressed in peak envelope power or mean power.  


- Glenn W9IQ


There is NO power at digital input - only a number usually representing a value between -1 and +1 at each sample.  Actually the best interface will be the optical one - thus not even electric connection between exciter and amplifier.


Title: RE: Goodbye tubes.
Post by: W9IQ on July 13, 2019, 05:48:22 PM
Humorous...

- Glenn W9IQ


Title: RE: Goodbye tubes.
Post by: SM0AOM on July 14, 2019, 01:04:11 AM

Harmonic stability can also be a case of making sure the exciter terminates harmonic power coming back down the link cable reasonably (Most don't), which is one of those things that makes me feel that building a transmitter usually trumps building an amplifier, much easier to the the transmitter case right when you control the whole damn chain, and it is not like small signal doings are notably expensive these days. The upside of dumping 90% of the exciter power into a pad is that a 10dB pad at least guarantees a 20dB return loss for the harmonics heading towards the rig, directly connecting puts the output part of the LPF across the gate network (phase rotated by the length of cable), this is not good.

This is quite often overlooked.
It turns out that limiting stage gains using feedback is very good for IMD suppression.

When the transition between bipolar and VMOS transistor came in the late 80s many designers used the increased stage gains for simplifying the transmitters. This often caused worse IMD performance compared to the bipolar chains.

Another aspect was that the low-pass filters at the output needed to have a "harmonic dump" as otherwise the reflected harmonics into the VMOS amplifiers made IMD performance markedly worse. It appears that reflected harmonics have less influence in bipolar transistor amplifiers.

Making an ISB-rated VMOS or LDMOS power amplifier is a major undertaking, and needs careful attention to feedback and gain distribution.


Title: RE: Goodbye tubes.
Post by: W1VT on July 14, 2019, 04:48:09 AM
Making an ISB-rated VMOS or LDMOS power amplifier is a major undertaking, and needs careful attention to feedback and gain distribution.

With relatively affordable standalone spectrum analyzers and other cheaper alternatives  you no longer need a facility like the ARRL Lab to build and test something like that.


Title: RE: Goodbye tubes.
Post by: W1BR on July 14, 2019, 07:33:45 AM
A clean two or three tone signal source is the problem for most of us.  Have the spectrum analyzers, but generating 100 watts with low IMD takes some work.


Title: RE: Goodbye tubes.
Post by: M0HCN on July 14, 2019, 08:04:51 AM
It is somewhat unclear to me that the optimum harmonic termination for linearity is actually the same as the 50R design value of the fundamental termination.

It is well known that playing with reflected harmonics can make a meaningful difference to efficiency, but I do wonder if there is another point where they can make a real difference to linearity? Anyone got a reference to the theory on this?

As to IMD test sources, If your rig is worse then the amp you are working on, fix the rig first, it will make more difference!

Note that high power single tone sources do not impose a linearity requirement, so a pair of class C 1kW stages can produce two tones that can then be combined in the usual way with 13dB of losses and still get your 100W of drive.

Regards, Dan.



Title: RE: Goodbye tubes.
Post by: SM0AOM on July 14, 2019, 08:45:21 AM

It is well known that playing with reflected harmonics can make a meaningful difference to efficiency, but I do wonder if there is another point where they can make a real difference to linearity? Anyone got a reference to the theory on this?

I have not seen any theory reference, but when designing HF MOSFET PA:s in the late 80s, ITT-Standard Radio ran into problems with both stability and linearity unless harmonic-dump LPF:s were used.

In their previous bipolar (BLX15) realisations, they did not have to use these measures to obtain ISB performance.

Marconi also ran into similar problems in their 500 W PA somewhat later.


Title: RE: Goodbye tubes.
Post by: AH7I on July 15, 2019, 02:50:50 AM
The problem with stability circles on a Smith chart is that it can be tricky to tell which side of the curve is the stable one...

The basics don't change and a newbie could still do worse then reading F.Termans magnum opus (Also, Langford-Smith).

73, Dan.

Thanks. 73, -bob ah7i


Title: RE: Goodbye tubes.
Post by: KB1GMX on July 15, 2019, 09:53:13 AM
I read the data sheet...

Its not wow neat!   It's rediscovered.  With many wrong assumptions.

First watch the rating for dissipation plastic tab cases have very high
thermal resistance so really good thermal design is a must.  Big
heatsink and fan.  However for the people that want to get their
QRP radio to impressive power it has possibilities.

As to paralleling, seriously?   The same guys make 1.5KW parts
and a pair of them combined would be far more resilient.
Generally paralleling at HF and up is not desirable as it
introduces more copper on the board with its issues, never
minding the paralleled parameters you don't want to increase.
I hold the MRF150 x4 amps that tend to sometimes do nasty
things.

Try to not apply 1980s design and devices to modern parts,
you will hurt yourself.  Newer parts are more robust and
have far better gain.  Also things like feedback are more
commonly used now.  The whole design process is more
sophisticated as well using modern simulation tools and
test techniques.  To me the 1970s was the beginning of
the big move to both bipolar power and various forms the
the VMOS first generation.

The biggest killer is far too much power in.  Maximum power
input the narrow band model is under a watt at then its over
driven!   That means the average (typically most) transceivers
the power spike will kill them before you get to say hellooo. 
Even a FT817 may be far too much!   Pin based limiters and
input attenuators are required as most 100W radios also are
not as nice and clean at low power if we ignore the ALC spiking
on key down.

Getting low IMD takes work as been said.  Also enough
standing current (BIAS) to required monitoring the heat.

Also even at 50V you want a low impedance load to the gates
and drains for stability and to keep on the linear part of the curve.
Been doing it for while like others here.  Going for max smoke is
usually a result without taking in all considerations.

An aside stage gain is not limited by the FCC for user designed
and built gear.  It was instituted to prevent US CB ops from
getting to the kilowatt level with COTS/HAM amps in one hop.

Allison



Title: RE: Goodbye tubes.
Post by: KM1H on July 15, 2019, 06:18:58 PM
Quote
An aside stage gain is not limited by the FCC for user designed
and built gear.  It was instituted to prevent US CB ops from
getting to the kilowatt level with COTS/HAM amps in one hop.

Allison

Which was aimed specifically at the National NCL-2000 with a pair of swamped grid driven 8122's. On 10M about 15-20W drive would provide ~1200W out. Ive run one on 6 since 1965 with a tuned input and a 270 Ohm resistor and run 1200W output with ~8W drive, No neutralization required and completely stable.

The FCC rule killed that amp for the ham market and left an almost complete production run in limbo. So National got even by moving production to North Central Maine and selling direct to the CBers, some hams, and also direct into Canada. The FCC never caught on and they were still producing them in Maine in small runs up to the IRS auction in 1992 ;D

Carl


Title: RE: Goodbye tubes.
Post by: KB8VUL on July 21, 2019, 08:06:00 AM
When building solid state amps, and this will raise some eyebrows, look at what the CB guys are doing.
There are guys out there running solid state amps at AM radio station power levels from vehicles. 

THe biggest historical issue with high power solid state at home was the power supply required. 
Tube stuff was easy, big transformer, some diodes, a filter cap and you had a plate supply.
Generating 48 volts at 50 amps was expensive.  Now, you can get switching power supplies and parallel them to produce any currnet level you could reasonably want.

The OP mentioned that he was looking to build a single band amp.  Why settle for single band, unless that's all you want.  The bandpass fillers are not hard to construct if you want multiband operation.
Solid state devices are here to stay, and they are in alot of applications better than tubes. 

But for some, nothing beats the glow of a tube.  And that's ok too.


Title: RE: Goodbye tubes.
Post by: K2FW on July 21, 2019, 02:29:19 PM

The Chinese FU728F Tetrode is rated for 1800 watts continuously and only cost about $400. Gain is about 15-16 dB depending on screen current. I have seen these tubes put out easily 2.3 KW in SSB mode with 60 watts drive. This tube was modeled after the 4CX1500B.

Mike, do you happen to know the "real" plate dissipation on the FU728F tube.  It must be more than 1500 watts since the tube is larger than a 4CX1500.


Title: RE: Goodbye tubes.
Post by: KM1H on July 21, 2019, 03:11:06 PM
The REAL rating is 1200W and it took about 2 seconds to find that spec sheet on Google. Since the tube is used for commercial and military amps that is a CCS rating.

You are welcome to apply any ICAS or Hammy Hambone IVAS rating you wish.

Carl


Title: RE: Goodbye tubes.
Post by: K2FW on July 21, 2019, 06:00:54 PM
The REAL rating is 1200W and it took about 2 seconds to find that spec sheet on Google. Since the tube is used for commercial and military amps that is a CCS rating.

You are welcome to apply any ICAS or Hammy Hambone IVAS rating you wish.

Carl

Thank You oh Humble one!


Title: RE: Goodbye tubes.
Post by: KM1H on July 21, 2019, 06:12:39 PM
Quote
Thank You oh Humble one!

Im always glad to be of service massa


Title: RE: Goodbye tubes.
Post by: W3RSW on July 22, 2019, 08:17:04 AM
W6ASI’s  Eimac Amateur Service Newsletter AS40 article
“Intermittent Voice Operation” and reprinted in Ham Radio Mag. Jan 1971
Defines such as a more realistic set of operating parameters to be found for Only specific tubes, the 8873/4/5 set in particular in this article.  Bill Orr writes that any other tube must be determined Individually; the parameters are not a universal set for all power tubes.

As such the IVAS rating is valid for SSB and CW for the particular oxide cathode ceramic triodes Specified and with reasons clearly outlined.

Tune up time limits and average operating power limits are defined.

https://archive.org/stream/hamradiomag/ham_radio_magazine/Ham%20Radio%20Magazine%201971/01%20January%201971#mode/2up


Title: RE: Goodbye tubes.
Post by: KM1H on July 22, 2019, 08:30:16 AM
And here is what ICAS is really all about from the horses mouth. IMO IVAS is simply a hammy hambone way to further decrease tube life especially with oxide cathode tubes. Those running the YC-156/YC-179 pulls have found that out the hard way.

https://www.americanradiohistory.com/ARCHIVE-RCA/RCA-Ham-TIps/RCA-Ham-Tips-39-10.pdf

Carl


Title: RE: Goodbye tubes.
Post by: KOP on July 22, 2019, 09:51:36 AM
W6ASI’s  Eimac Amateur Service Newsletter AS40 article

W6SAI perhaps?


Title: RE: Goodbye tubes.
Post by: W3RSW on July 23, 2019, 08:15:51 AM
Certainly, Bill Orr himself, “Mr. Eimac”
 ;) And the modern, well reasoned article in the reprint bears reading, starting page 24.


Title: RE: Goodbye tubes.
Post by: K2FW on July 23, 2019, 08:22:40 AM
Certainly, Bill Orr himself, “Mr. Eimac”
 ;) And the modern, well reasoned article in the reprint bears reading, starting page 24.
An excellent read.  I've had many Bill Orr books over the years.  What I really would like to know is how does the plate dissipation of the FU728F compare to the 4CX1500?  The tube is much larger in size than a 4CX1500.


Title: RE: Goodbye tubes.
Post by: KM1H on July 23, 2019, 10:19:15 AM
Certainly, Bill Orr himself, “Mr. Eimac”
 ;) And the modern, well reasoned article in the reprint bears reading, starting page 24.
An excellent read.  I've had many Bill Orr books over the years.  What I really would like to know is how does the plate dissipation of the FU728F compare to the 4CX1500?  The tube is much larger in size than a 4CX1500.

Are you saying the spec sheets arent sufficient for you?



Title: RE: Goodbye tubes.
Post by: K2FW on July 23, 2019, 12:48:35 PM
Certainly, Bill Orr himself, “Mr. Eimac”
 ;) And the modern, well reasoned article in the reprint bears reading, starting page 24.
An excellent read.  I've had many Bill Orr books over the years.  What I really would like to know is how does the plate dissipation of the FU728F compare to the 4CX1500?  The tube is much larger in size than a 4CX1500.

Are you saying the spec sheets arent sufficient for you?


Please respond when you have something useful to contribute.  Otherwise, just shut up!


Title: RE: Goodbye tubes.
Post by: KA4WJA on July 23, 2019, 02:57:21 PM
Steven,
Seriously?
Please respond when you have something useful to contribute.  Otherwise, just shut up!
The reason I'm confused (and asking if you're serious or just joking?), is because I was going to point you to some detailed info /discussion....but since Carl gave you the short answer, I thought the long answer might be treated with as much rudeness as Carl's succinct answer.  :(


I mean, I thought Carl answered you directly 2 days ago...
The REAL rating is 1200W and it took about 2 seconds to find that spec sheet on Google. Since the tube is used for commercial and military amps that is a CCS rating.

You are welcome to apply any ICAS or Hammy Hambone IVAS rating you wish.

Carl


But, taking a chance here...
So, if that isn't sufficient, how about you do a quick search and find the info you desire?
However, perhaps you are unable to do so, and so I will try to be a good ham and point you in the right direction... :)


Have a look here for a quite detailed discussion about the FU728F:
https://www.eham.net/ehamforum/smf/index.php/topic,87663.0.html

Or maybe you just want the datasheet (which is allover the internet):
http://www.ok1rr.com/tubes/FU-728F.pdf

Or maybe you'd like some discussion from the contesting reflector:
http://lists.contesting.com/archives//html/Amps/2012-06/msg00315.html


Or maybe all of that doesn't give you what you desire?
So...

So, how about a quick half-dozen bullet-points:
 -- The FU728F has a larger base centering pin, thereby making it incompatible with the 4CX1500b's socket.  But a 4CX1500b will fit in a FU728F socket.

-- The FU728F and 4CX1500b use different filament voltages.

-- The FU728F is less linear than the 4CX1500b, which means even a little too much screen current and you're splattering up/down the band. (even if operated properly, the FU728F isn't the tube to use for clean high-power SSB service, but then again the 4CX1500b is the rare exception for a power tetrode...and depending on how dirty your exciter / transceiver is, perhaps this is a moot point?)

--  Ironically many hams either ignore, or are ignorant of, this poor linearity of the FU728F, but seem to hype this tube's higher gain compared to the 4CX1500b.

-- Remember, if wishing to ignore the poor linearity AND also pushing the tube beyond US legal limits, while it will do this, in addition to you needing to understand how to minimize your transmit IMD, you will need to understand that this is not a 2.5kw CCS tube, no matter how "big" you perceive the anode cooling fins are.

-- (according to anecdotal reports) The FU728F's higher (than the 4CX1500b's) internal capacitance reduces it's gain on the higher HF bands / makes the output tank circuit design more critical.



Now, Steven, I hope this helps....

73,  
John, KA4WJA

P.S.  I gave serious thought to just ignoring you....as I personally feel (just my opinion) that in answering your question after you've been so rude/insulting, could just encourage continued rudeness??
But, taking a chance here.... :)




Title: RE: Goodbye tubes.
Post by: KM1H on July 25, 2019, 09:39:49 AM
Quote
P.S.  I gave serious thought to just ignoring you....as I personally feel (just my opinion) that in answering your question after you've been so rude/insulting, could just encourage continued rudeness??
But, taking a chance here.... Smiley

I guess he is still on a potty break John ::)


Title: RE: Goodbye tubes.
Post by: K6AER on July 25, 2019, 04:40:39 PM
Quote:
“-- The FU728F is less linear than the 4CX1500b, which means even a little too much screen current and you're splattering up/down the band. (even if operated properly, the FU728F isn't the tube to use for clean high-power SSB service, but then again the 4CX1500b is the rare exception for a power tetrode...and depending on how dirty your exciter / transceiver is, perhaps this is a moot point?)

--  Ironically many hams either ignore, or are ignorant of, this poor linearity of the FU728F, but seem to hype this tube's higher gain compared to the 4CX1500b.

-- Remember, if wishing to ignore the poor linearity AND also pushing the tube beyond US legal limits, while it will do this, in addition to you needing to understand how to minimize your transmit IMD, you will need to understand that this is not a 2.5kw CCS tube, no matter how "big" you perceive the anode cooling fins are.

-- (according to anecdotal reports) The FU728F's higher (than the 4CX1500b's) internal capacitance reduces it's gain on the higher HF bands / makes the output tank circuit design more critical.”

The FU728F linearity is fine and equal or better than the coveted 4CX1500B.

On my amplifier the IMD from the 2 carrier mix (on 20 and 40 meters)  to the third IMD mix is down 35dB peak to peak. 5th and 7th were down an additional 10-15 dB. These reading were taken at 1700 watts out. Gain on ten meters is about the same as eighty meters at about 14-15 dB. Even in the same amplifier that provides 2.3 Kw on 160-10 meters, the 6 meter output is over 1700 watts. High frequency gain loss is not a function of the tube but of the stray inductance and capacitance in the dual Pi networks. OM Power has developed a better matching network in their amplifier and offer a single tube amplifier for 160-6 meters.

This tube has been in manufacturing for over 25 years. Emtron and OM Power have built many fine amplifiers using this product and the tube holds up fine in high-power contesting. Hams worldwide have been using this tube for many years. I have been using this tube every day for the last three years with no problems.


Title: RE: Goodbye tubes.
Post by: NN2X on July 28, 2019, 05:46:20 PM
The Chinese FU728F Tetrode is rated for 1800 watts continuously and only cost about $400. Gain is about 15-16 dB depending on screen current. I have seen these tubes put out easily 2.3 KW in SSB mode with 60 watts drive. This tube was modeled after the 4CX1500B.
[/quote]

Yep, I had a Emtron DX 3SP, with a pair of those Tubes, and the output on 20 meters, 5KW...PEP..

The price used is about 4,000 (USD)..



Title: RE: Goodbye tubes.
Post by: K6AER on July 31, 2019, 06:40:17 PM
The Chinese FU728F Tetrode is rated for 1800 watts continuously and only cost about $400. Gain is about 15-16 dB depending on screen current. I have seen these tubes put out easily 2.3 KW in SSB mode with 60 watts drive. This tube was modeled after the 4CX1500B.

Yep, I had a Emtron DX 3SP, with a pair of those Tubes, and the output on 20 meters, 5KW...PEP..

The price used is about 4,000 (USD)..


[/quote]

Is Rudy running still Emtron?


Title: RE: Goodbye tubes.
Post by: ZL4IV on August 09, 2019, 11:28:28 PM
Still good support from Rudy and Dan. He made a run of amps last year but haven't looked into what they are up to now. I still service these amps in NZ. In fact these amps are so closely related through the series I was able to point to a fault via email from NA in a DX3-sp, internal connector, the guy just pushed it all the way in, fixed. The FU728F are great tubes and they are clean, as with most issues it's the nut behind the wheel that's loose.

Do you remember the days of AM when there was no 'your off frequency' channelized rubbish, almost no hams had spectrum analyzers. How did we come to this nonsensical debating about perfection. Look for a fault in another and you will find it.


Title: RE: Goodbye tubes.
Post by: ZL4IV on August 09, 2019, 11:32:52 PM
Oh, I forgot to mention the SS Finals do wear out. Something called junction barrier migration. They will eventually go POP!


Title: RE: Goodbye tubes.
Post by: W1QJ on August 10, 2019, 05:38:52 AM
These tubes sell for even less than $400 if you can buy them direct from China or have some picked up in China.  They seem to have a better record of NOT being problematic like Chinese glass tubes.  At 1500 watts they are actually quite clean and run cool as they do have a large cooling anode structure.  They are tetdrodes and therefore require the screen and bias supplies and associated circuitry to build around them and due to the attract pricing several amplifier companies offer them in their amps.  If a similar tube in a triode was avaialabe at an equal price it would be even better!


Title: RE: Goodbye tubes.
Post by: KM1H on August 10, 2019, 06:14:18 AM
If only Eimac had released their instant on 3CX1000A7 (actually 1500W PD in normal AB2 Linear use and NOT ICAS) in a version with a 8877 base! What a great tube and bullet proof unlike the 3CX1200 crap variations they sold for decades.

https://frank.pocnet.net/sheets/140/8/8283.pdf

I bought mine as a CH 13 TV translator pull over 30 years ago for the HB 1500W 2M amp. It still will run 1800W key down at the same 100W drive.




Title: RE: Goodbye tubes.
Post by: K6BRN on August 10, 2019, 06:16:16 PM
Rex (ZL4IV):

Quote
Oh, I forgot to mention the SS Finals do wear out. Something called junction barrier migration. They will eventually go POP!

Transistor wearout curves are time/temperature/voltage dependent.  The exact mechanism varies a bit with transistor type and geometry.  But if properly designed and not (terribly) abused, SSPAs will last decades in continuous use.  Commercial SSPAs routinely last 15+ years at 100% duty cycle with >90% probability of success.

Just one reason why transistors are not plug-in consumable devices in HF amplifiers.

Brian - K6BRN


Title: RE: Goodbye tubes.
Post by: ZL4IV on August 10, 2019, 11:18:47 PM
Exactly, both systems last for decades is used properly. Instant on seems to be an advantage over some non instant on tube types.


Title: RE: Goodbye tubes.
Post by: AC2RY on August 11, 2019, 09:49:50 AM
Exactly, both systems last for decades is used properly. Instant on seems to be an advantage over some non instant on tube types.


Solid state amplifiers are NOT really "instant on". It takes 10-20 seconds to start up control processor and do initial self-check before amplifier is ready to transmit. Though unlike tube amplifiers they have a negligent "stand by" power consumption and thus can be left in that state indefinitely long.


Title: RE: Goodbye tubes.
Post by: G3RZP on August 11, 2019, 01:03:41 PM
Solid state life is very temperature dependent. Tunnel diodes, for example, being very highly doped, fail generally in ten to thirty years at room temperature, although there are exceptions - that is because of diffusion at room temperature. At Plessey Semiconductors, at the other extreme, we made transistor arrays guaranteed to operate for 30 minutes - at 260C - and medical implant devices intended for over a 20 year life at body temperature.

NASA demanded that test data on space qualified parts be kept for 25 years after delivery. That data was on 15 inch discs....25 years later, I believe that there was one specialist firm in the US who could read such discs and charged accordingly! But data book from those days are still available....


Title: RE: Goodbye tubes.
Post by: W1VT on August 11, 2019, 03:32:45 PM
I recall that the owners of the old Ten Tec Argonaut QRP rigss loved using the radios so much that they would wear out the finals!  But I don't think anyone really complained considering how much fun they had.  And replacing them wasn't that hard.


Title: RE: Goodbye tubes.
Post by: KM1H on August 11, 2019, 05:19:01 PM
Quote
NASA demanded that test data on space qualified parts be kept for 25 years after delivery. That data was on 15 inch discs....25 years later, I believe that there was one specialist firm in the US who could read such discs and charged accordingly! But data book from those days are still available....

I spent many hours working on IBM and Memeorx drives with those disks all the way back to 10 mb single platter ones.


Title: RE: Goodbye tubes.
Post by: W9IQ on August 11, 2019, 06:26:09 PM
These are not your grandpa's solid state devices.

A modern LDMOS device, such as the popular BLF188XR can do 1400 watts at 5 watts of pulse drive. The estimated average (MTTF) lifetime with a 50 volt bus is north of 100,000 years when run with a 90 °C case temperature. That is a 100% duty cycle rating, not some goofy tube ICAS rating.

There is no commercial tube that comes within three orders of magnitude of that lifespan. If you are a solid state skeptic, divide that life by 1000 and you still beat out any tube by a couple of generations of ownership.

- Glenn W9IQ


Title: RE: Goodbye tubes.
Post by: AC2RY on August 11, 2019, 09:44:04 PM
The estimated average (MTTF) lifetime with a 50 volt bus is north of 100,000 years when run with a 90 °C case temperature.

- Glenn W9IQ

I think you make a mistake here - stated life span of semiconductors is usually 100,000 HOURS, not YEARS. Still means 11 years of non-stop operation. Other parts like capacitors will start failing sooner than that.


Title: RE: Goodbye tubes.
Post by: K6BRN on August 11, 2019, 09:45:11 PM
Some comments...

Quote
Solid state amplifiers are NOT really "instant on". It takes 10-20 seconds to start up control processor and do initial self-check before amplifier is ready to transmit.

Well, my KPA-500 is up any ready ro go in less than two seconds (just tried it) and my Yaesu Quadra is up and running in about 5.  Close enough to "instant on" for me.  And their idle power is almost nothing compared to my tube amps, plus moving them around (minor shock and vibration) does not seem to bother them one bit, unlike tube amps.  BTW, my SB-200 takes about 3 seconds and a buddies Henry 2K takes about five.

Glen (W9IQ): 

Quote
The estimated average (MTTF) lifetime (...referring to an LDMOS device...)with a 50 volt bus is north of 100,000 years when run with a 90 °C case temperature.

Might not want to jump on that bandwagon just yet.

Trust me (or don't).  The practical life of LDMOS devices is not 100,000 years, nor is its true MTTF.  The service life (or MTTF) of a rock isn't 100,000 years.  Just look at the pryamids. :)  It's very interesting marketing based on less than brutally honest and realistic conditions generally built on simplified models of the gate oxide. There are MANY failure mechanisms still unaccounted for and there is still WAY too little data on this type of part, plus  major geometry details, metalization, doping profiles, embedded protection structures and many more issues are still evolving.  Which is one reason why they are still not used in Hi-Rel applications.

They have a LOT of promise.  But like so many (relatively) new technologies, unrealistic claims set by companies promoting them can actually poison the market if they are taken as the literal truth.  And frankly, my industry, which is built on Hi-Rel, doesn't trust anybodies claims.  We check.  For a reason.  I recall the long-life claims made when GaAs LEDs first came into wide availability with quoted service lifetimes >100 years back in the '70's.  Did NOT happen - those early devices dimmed pretty fast.  And that was just 100 years.  Remember the long-life promise of Lithium-Ion batteries?  The 787 and quite a few consumer products had some major "oooops!" (and Ka-BOOM!) moments before they matured (so much for long life!).  And they are still maturing.

Give LDMOS time.  It'll mature, too.  In the meantime the current devices seem to be working pretty well in amateur amps.

Brian - K6BRN





Title: RE: Goodbye tubes.
Post by: G3RZP on August 12, 2019, 02:16:47 AM
Both Voyager spacecraft have been operating for over 350,000 hours. The Swindon factory that made some of the integrated circuits supplied for them has been a hole in the ground for about 26,000 hours....having only lasted about 510,000 hours....

There was a UHF TV tx in Germany which, quite a few years back, was mentioned in the electronics press as having taken a klystrode out of service at 110,000 hours and sent it to a sister station because it still met full specification......but that is unusual, to say the least.


Title: RE: Goodbye tubes.
Post by: W9IQ on August 12, 2019, 07:41:08 AM
I correctly stated years - but I had one too many zeros. It is 10,000 years. It is not hours.

Even if you discount MTTF by a factor of 100, you still have more than 875,000 hours of continuous operation. There is not any tube that is close to this type of MTTF specification.

Regarding other components that make up the amplifier, of course they will have a shorter lifetime in most cases. This is common to both amplifier topologies.

- Glenn W9IQ


Title: RE: Goodbye tubes.
Post by: KM1H on August 12, 2019, 07:41:40 AM
The original Eimac 3-500Z's in my one owner 1986 Amp Supply LK-500ZC are still producing the same 1200W at the same 75-80W drive level.  It is rather well known that it has been run hard and put away wet after serious 48 hour contests and lots of DX pileups and more recently as an AM linear at the same 1200W PEP. Those tubes certainly stay gettered ;D

That is certainly not a longevity record of hours producing RF but does show how well the "silly ICAS" spec can work with high quality products.  Unlike the seriously overated Russian and Chinese copy 811's being run as 811A's.

Carl


Title: RE: Goodbye tubes.
Post by: KM1H on August 12, 2019, 08:07:33 AM
Quote
I correctly stated 100,000 years. It is not hours.

Citation please

Quote
Regarding other components that make up the amplifier, of course they will have a shorter lifetime in most cases. This is common to both amplifier topologies.

In MOST cases??  While electrolytic caps have a finite life the more recent ones are already passing 30 years and a decade longer in some cases. External PS are common for SS amps and are conveniently not mentioned in the complaints columns. Fans are common to all. There are more relays in a SS amp and reported failures are common.

The low power draw on standby for SS is a fallacy as the most popular series of ALS-1300 and 1306 draw about 100W which is often more than indirect heated filament amps of the same or even double the power level.

And the list goes on. I'll stick to tubes thank you as Im more interested in long term reliability than marketing hype.
The several other amps used here all have tube date codes from the 60's to 80's and produce rated power.

I am certainly not against SS where it is needed and worked with it professionally from the 70's at Sr Tech to Sr Engineer positions until retirement.

OTOH the US military is apparently returning to hollow state for some critical applications and the Russians havent stopped AFIK.

Carl


Title: RE: Goodbye tubes.
Post by: W9IQ on August 12, 2019, 08:25:40 AM
Carl,

Do note that I corrected my post to 10,000 years - and that is with a relatively high case 90 °C temperature. You can go up another order of magnitude with a more aggressive cooling package.

You can use Ampleon's reliability calculator at:

https://www.ampleon.com/products/broadcast/0-500-mhzrf-power-transistors/BLF188XR.html (https://www.ampleon.com/products/broadcast/0-500-mhzrf-power-transistors/BLF188XR.html)

Regarding my comment that "most" components will have a shorter lifetime, components that might not could include things like baluns, splitters, inductors, PCBs, heatsinks, etc. That is why I said "most" rather than "all".

The idling current issue is a question of the amplifier design and it is not a given with all solid state amps. But then a single 3-500Z will draw ~75 watts on the filament alone if it isn't switched off during standby - also a question of the amplifier design.

My broader point is that modern LDMOS solid state finals now far exceed the lifetime of any tube. Lots of other facets can be discussed but the dagger is in the device MTTF question.

- Glenn W9IQ


Title: RE: Goodbye tubes.
Post by: W0BTU on August 12, 2019, 08:33:23 AM
That's interesting, but how about the IMD specs as compared to good tubes?

These are not your grandpa's solid state devices.

A modern LDMOS device, such as the popular BLF188XR can do 1400 watts at 5 watts of pulse drive. The estimated average (MTTF) lifetime with a 50 volt bus is north of 10,000 years when run with a 90 °C case temperature. That is a 100% duty cycle rating, not some goofy tube ICAS rating.

There is no commercial tube that comes within three orders of magnitude of that lifespan. If you are a solid state skeptic, divide that life by 1000 and you still beat out any tube by a couple of generations of ownership.

- Glenn W9IQ


Title: RE: Goodbye tubes.
Post by: AC2RY on August 12, 2019, 11:18:02 AM
That's interesting, but how about the IMD specs as compared to good tubes?



If used no higher than -3dB below rated power along with moderate negative feedback transistors have IMD comparable with tubes. When you get into clipping, distortions from transistors raise much more quickly than from tubes. But this was well known for over 50 years, that is why guitar amplifiers still mostly use tubes.

But somehow people complain about distortion at clipping level. Transistors at rated power should only be used for CW mode, nothing else. To amplify any wide band signal -3dB is a reasonable design limit.




Title: RE: Goodbye tubes.
Post by: KM1H on August 12, 2019, 11:47:20 AM
Quote
But somehow people complain about distortion at clipping level. Transistors at rated power should only be used for CW mode, nothing else. To amplify any wide band signal -3dB is a reasonable design limit.
 

Clipping also occurs with CW especially when the final tubes are biased quite deep into Class C. I suspect similar occurs with overdriven SS.

Carl


Title: RE: Goodbye tubes.
Post by: G3RZP on August 12, 2019, 01:24:53 PM
Deep space probes do have an advantage in that ambient temperatures are low - but all the heat has to be radiated. Still, 40+ years isn't a bad record for pretty well continuous operation, although there is a carbon filament lamp in a fire station in, I believe South Carolina, that hasn't, it is claimed, been off since 1912.


Title: RE: Goodbye tubes.
Post by: W0BTU on August 12, 2019, 01:38:44 PM
I suspect you're right. :-)  Otherwise, key click QRM is inevitable.

Clipping also occurs with CW especially when the final tubes are biased quite deep into Class C. I suspect similar occurs with overdriven SS.


Title: RE: Goodbye tubes.
Post by: AC2RY on August 12, 2019, 01:45:28 PM


Clipping also occurs with CW especially when the final tubes are biased quite deep into Class C. I suspect similar occurs with overdriven SS.

Carl

When you only have CW signal - there is (almost) no IMD - only harmonics, which can be easily filtered out.

Tubes do clip, but raise of high order harmonics and IMD is much slower. That is why tubes can be overdriven (HAMs commonly do that) with less impact on signal quality.


 


Title: RE: Goodbye tubes.
Post by: K6BRN on August 12, 2019, 02:52:30 PM
A few comments about Voyager...

There have been quite a few failures in the spacecraft electronics, none fatal so far.  And the thermoelectric generators are close to exhaustion, even at minimal power draw.  At some point the sun sensor will lose lock and the power will drop just too low, and they're gone.  But they HAVE been a remarkable success.  The CPUs are Silicon on Sapphire parts that are rad hard and run at (it's been a while, here...) about 10V in this application (16V is also running around in the back of my memory for some reason)  Initially there were three voted CPUs, now they are operating in stand-alone mode, one at a time, last I heard.  I believe the RF amp for T&C is an SSPA.  And yes, capacitors are problematic - especially tantalum types.

GEC/Plessy made some of the semiconductor parts, Hughes Silicon Operations (now long gone as well) made others.  SoS was a major space process back then.

Regarding heat in spacecraft electronics - they get pretty hot, which is one reason why heat pipe cooling is commonly used and why the preferred part temperature grade is 125C.  In a hard vacuum (great insulator), cooling is all by radiation from the spacecraft body while the best internal cooling is by conduction (hence, heat pipes).  Often, one side of the spacecraft broils while the other freezes.  Heaters are commonly used when electronics are powered down or in "cold" trajectories.  Same with the Mars rovers. Hughes "spinners" solved a lot of this problem by rotating the entire spacecraft to provide axial stabilization AND equalize thermal loads.  Great products.

On Glenn's comments - he is right in that both the shelf life and service life of solid-state devices usually far exceed that of tubes.  For one, hydrogen and helium infiltration is much less of an issue.  Most consumers spend zero time tinking about that, but its a real problem and happens wheter or not the tube is energized.  Metal cased tubes are pretty good in that regard, glass enveloped tubes, not so much.  Regardless, LDMOS teachnology is new, and when I was talking about "other failure modes" I was talking about the ones not yet adequately characterized and analyed that exist within the transistor structure itself.  It's not just the junction.  And there are embedded protection and parasitic devices on the transistor die itself, metallization and passivation.  They all have their own failure modes to consider.  LDMOS is still too new to have accumulated adequate failure data, via testing or in-service results, hence they are NOT generally found in HiRel applications.  But maybe one day...

Brian - K6BRN


Title: RE: Goodbye tubes.
Post by: K6BRN on August 12, 2019, 02:54:13 PM
....Forgot to mention, the CPUs are the venerable 1802 microprocessors.  Look up RCA COSMAC 1802.

Brian - K6BRN


Title: RE: Goodbye tubes.
Post by: K4EMF on August 12, 2019, 04:03:50 PM
I take it we're WAY past the point of just agreeing that both tube and solid state amps have advantages and disadvantages and which is "better" depends on how it's used and user preferences?

 


Title: RE: Goodbye tubes.
Post by: K6BRN on August 12, 2019, 07:35:13 PM
Jay (K4EMF):

Quote
I take it we're WAY past the point of just agreeing that both tube and solid state amps have advantages and disadvantages and which is "better" depends on how it's used and user preferences?

Yep.  This is a hobby.  What you enjoy using is the best choice.  Until the next toy.  Then THATS the best.  :)

Brian - K6BRN


Title: RE: Goodbye tubes.
Post by: G3RZP on August 13, 2019, 12:29:34 AM
Brian,

It is slightly ironic that the ICs have longer life than the companies and factories that made them!

There are bipolar Plessey Process 3 frequency dividers in the Voyagers. Process 3 was remarkably rad hard - some radar logarithmic amplifiers assembled onto a hybrid alumina substrate and irradiated to the point where the alumina turned from white to brown (and given four weeks to 'cool' so they could be handled!) still tested out to the full spec.

The joke in the factory was 'Where are the little green men going to park their flying saucer when they come wanting some parts?'


Title: RE: Goodbye tubes.
Post by: KM1H on August 13, 2019, 05:58:19 AM
Quote
On Glenn's comments - he is right in that both the shelf life and service life of solid-state devices usually far exceed that of tubes.  For one, hydrogen and helium infiltration is much less of an issue.

Id consider that a stretch as there are literally thousands of tubes (lets call them "small signal" or as listed in RCA, Sylvania, GE, and other Receiving Tube manuals) from the 1920's and on that are still 100% useable with no noticeable air ingress. Im sure the thousands of vintage electronics users, ham and otherwise, would agree....me included as I still 'fess up to using them on an almost daily basis and have several thousand on hand.

Larger TX power tubes DO  develop glass to metal seal leaks but they tend to be either type or brand specific. Later WW2 production tended to be built for short and not long term survival but still there are exceptions in great quantities.

Since we dont have ~90-100 year old transistors (or IC's) to compare the subject is moot.

Carl


Title: RE: Goodbye tubes.
Post by: W9IQ on August 13, 2019, 08:25:32 AM
Hey - I am the one from Missouri. You are not allowed to co-opt our "show me" signature!

- Glenn W9IQ


Title: RE: Goodbye tubes.
Post by: W9IQ on August 13, 2019, 08:37:43 AM
I was going to say that this is what happens when you live in a vacuum  - but I didn't want you to take that the wrong way...

- Glenn W9IQ


Title: RE: Goodbye tubes.
Post by: K6BRN on August 13, 2019, 08:39:17 AM
Hi Peter (G3RZP):

Good to hear from you again!  Yes...  we've discussed this before...

Quote
It is slightly ironic that the ICs have longer life than the companies and factories that made them!

And it's incredible that some of our space products are headed into interstellar space ... and are still (nominally)... functional.  I will always be proud of that.  As well as the near-earth spacecraft that people use every day ... yet have no idea that their services and safety are ensured by these vehicles.  For the most part, they just work.  It's nice to know we've had a positive impact on the world.

Carl (KM1H):

Quote
Id consider that a stretch as there are literally thousands of tubes (lets call them "small signal" or as listed in RCA, Sylvania, GE, and other Receiving Tube manuals) from the 1920's and on that are still 100% useable with no noticeable air ingress.

Nothing moot about the reliability and lifetime advantage of solid-state devices vs. thermionic valves (tubes).  My career spans the point from when the SAGE (SAC) computer system that once protected the USA to the end of the NIKE era, where Japan maintained their systems well into the '80s.  Both were tube based and I was involved in the latter as a young engineer.  Later, at Hughes, we used a mixture of "tube" devices and solid state, phasing into solid state for their inherent ruggedness and reliability.  I had an entire Specialty Engineering team in my organization before I retired, and am working with reliability & components engineers again, today, in Career Mark II.  Every product I design or help design is all about reliability.  With modern Hi-Rel devices (and even 20 year old ones), solid state wins in the reliability tests (accelerated life tests) almost every time.  And I say almost, because there are devices that you probably would not even recognize as tubes (such as specific types of purpose built TWTAs) that are so good, their useful lifetimes used to overlap with emerging SSPA technology.  Not so much anymore.

Easy to check... look up the MTBF of the tube based SAGE computer system vs. the early IBM System/360's.  It's part of the historical record.  There are literally orders of magnitude differences in reliability.

Quote
Since we dont have ~90-100 year old transistors (or IC's) to compare the subject is moot.

But we do!   Every manufacturer of Hi-Rel and every space company has bushels of transistors (and other devices) that technically have more than 100 years of service life on them, via hi-temperature, hi-voltage Accelerated Life Testing.  It's traditional to screen every lot of parts before the remainder are used and to CHARACTERIZE their wearout curves before they are designed in.  We used to take the survivors home for projects.  I still have boxes of them.  Pretty tough devices, if properly built.

LDMOS is still too new to have an adequate base of information in this area, for HiRel applications, and devices in this technology are evolving very rapidly.  Does NOT mean they are bad - they're probably excellent, based on very early indications.  Just need more data to analyze from multiple manufacturers to fully understand their capabilities before putting them in zero-maintenence systems and expecting them to meet specs for more than 15-40 years with >90% confidence.

Brian - K6BRN





Title: RE: Goodbye tubes.
Post by: K6BRN on August 13, 2019, 08:44:06 AM
Good Grief, Glenn!

Quote
Hey - I am the one from Missouri. You are not allowed to co-opt our "show me" signature!

Quote
Insert Quote
I was going to say that this is what happens when you live in a vacuum  - but I didn't want you to take that the wrong way...

- Glenn W9IQ

You're evolving a sense of humor!  Bravo!  Excellent! (and I DO mean this!)

Discussions will be MUCH more fun, now.

DE Brian - K6BRN

(Ever trying, ever failing comedian.  But its the "trying" part that counts!)



Title: RE: Goodbye tubes.
Post by: G3RZP on August 13, 2019, 08:45:22 AM
Mullard OC170 and OC171 germanium VHF transistors are notorious for failing after 30 to 40 years because of whiskers growing in the metallisation and shorting the junction. Then there was 'purple plague' and 'white plague' in integrated circuits causing failure. Another failure we had in dual in line plastic devices occurred when the assemblers in the Philippines changed from a powder filler for the plastic to very short glass rods: moisture crept down them and led to metallisation corrosion. Of course, the assemblers hadn't told us...


Title: RE: Goodbye tubes.
Post by: N0YXB on August 13, 2019, 09:47:33 AM
I was going to say that this is what happens when you live in a vacuum 


That's a good one, thanks for the chuckle.   :)


Title: RE: Goodbye tubes.
Post by: KM1H on August 13, 2019, 10:24:46 AM
Germanium transistors are notorious for excessive leakage these days and millions of them were in all sorts of applications, including military, in the US, UK, etc. Same thing with the SS diodes. And it includes those still new in original packaging.
Yet vacuum tubes of the same era and earlier are 100% out of the old box. Plug n Play.

Even the F-16 still uses them.

Repeating tales of old spacecraft SS is interesting but proves nothing since they are such a tiny meaningless special application percentagewise and many that are still working are well past their usefulness.....just more space garbage. Plus what is used in the TX amp stages?

Hollow state has also played a part in radiation hardened NASA computers in recent years.

Carl







Title: RE: Goodbye tubes.
Post by: K6BRN on August 13, 2019, 02:48:09 PM
Hi Peter (G3RZP):

Quote
Mullard OC170 and OC171 germanium VHF transistors are notorious for failing after 30 to 40 years because of whiskers growing in the metallisation and shorting the junction. Then there was 'purple plague' and 'white plague' in integrated circuits causing failure. Another failure we had in dual in line plastic devices occurred when the assemblers in the Philippines changed from a powder filler for the plastic to very short glass rods: moisture crept down them and led to metallisation corrosion. Of course, the assemblers hadn't told us...

Yep... very much remember the tin whisker problems, "purple plague", etc., which is why LDMOS is not yet mature enough for HiRel applications.  Still lots of reliability unknowns.  As I said, not a black mark, just need more time, test data and analysis.  Still.... 30 to 40 YEARS to failure.  Not too shabby.

Carl (KM1H):

Quote
Repeating tales of old spacecraft SS is interesting but proves nothing since they are such a tiny meaningless special application percentagewise and many that are still working are well past their usefulness.....just more space garbage. Plus what is used in the TX amp stages?

(Sigh!).  You do realize that there are more spacecraft in orbit and in service today than ever before in history, and that you use them every minute without ever being aware of the massive number of services they provide?  Perhaps not.  That's called "success", in my business, BTW.

Per your question, we use transistors in every stage of the TX chain, from small signal to SSPA.  Just like cell towers do.  TWTAs are still there in older and specialty payloads, but are fading to the background in favor of SSPAs, often in phased array antennas.  And although SSPAs are emissions type devices, they do not look, smell, work like or feel like a 3-500Z, 6146, T160L or any other of your favorite tubes.

About reliability ...

HiRel and space is all about, well... reliability.  Often (but not always) the items characterized for HiRel are the same devices you use every day, just screened to a different standard.  So that's where the data and analysis is.  And it says you are wrong.  No need to prove it. It's been done by the IEEE, XRTC, ESA, NASA, "Circle A" and many, many other respected technical bodies.  Tube based systems and devices are generally orders of magnitude less reliable than solid state.  Hard to argue with that big a difference, regardless whether or not a few 1920's tubes still flicker to life in niche hobby applications.

Technology will move on one day.  but today, we are in the solid-state era.

About computers based on tubes.  You mean nanoscale ionic switches (which, oddly enough are STILL called "transistors")?  Not tubes.  And not here yet, either.  We'll have to wait and see what happens over the next 20 years or so.  Personally, my bet is on Duotronics.  :)

For a number of years my team virtually owned the market for PPC750 based very high performance bus and unit computers for space.  Now, in Career Mark II, I buy computers for space.  Plenty of suppliers.  Have yet to find a single tube in any of them.

You seem to label a lot of things you do not understand "Garbage".  Which indicates you are not open to learning in these areas.  Maybe you should reconsider - life and technology is moving on, and its much more fun to move with it.  Really.

Best Regards,

Brian - K6BRN







Title: RE: Goodbye tubes.
Post by: W9IQ on August 13, 2019, 02:51:29 PM
This has become a strange mix of shelf life vs operating life comparisons.

The LDMOS has more continous, full power operating life (MTTF) than any tube final by several orders of magnitude.

- Glenn W9IQ


Title: RE: Goodbye tubes.
Post by: W9IQ on August 13, 2019, 04:21:34 PM
Maybe some people have too much on their plate...

- Glenn W9IQ


Title: RE: Goodbye tubes.
Post by: KM1H on August 13, 2019, 05:22:56 PM
Quote
The LDMOS has more continous, full power operating life (MTTF) than any tube final by several orders of magnitude.

The gating factor in most commercial applications is not the individual device life but rather the operational life of the product it is in. With LDMOS that is just a guess at this point.

Carl


Title: RE: Goodbye tubes.
Post by: W9IQ on August 13, 2019, 05:41:36 PM
Quote
The LDMOS has more continous, full power operating life (MTTF) than any tube final by several orders of magnitude.

The gating factor in most commercial applications is not the individual device life but rather the operational life of the product it is in. With LDMOS that is just a guess at this point.

Carl

So what is the MTTF under continuous operation of your favorite tube that is used in amateur applications?

- Glenn W9IQ



Title: RE: Goodbye tubes.
Post by: K6BRN on August 13, 2019, 06:16:14 PM
Glenn (W9IQ):

Quote
Maybe some people have too much on their plate...

- Glenn W9IQ

Ack!  OK.  Definitely got a chuckle out of THAT one!

Quote
The LDMOS has more continous, full power operating life (MTTF) than any tube final by several orders of magnitude.

Yes.  It is almost certainly true just by the nature of the devices (tube vs. transistor wearout curves).  This is, in fact, a REALLY silly debate.  If Carl likes tubes and believes them to be the best, most reliable device family there is there is, so be it for him.  It's just "Carlworld", as usual.  No need to grid (sic) your teeth over it.

Brian - K6BRN


Title: RE: Goodbye tubes.
Post by: KM1H on August 13, 2019, 06:20:44 PM
Quote
So what is the MTTF under continuous operation of your favorite tube that is used in amateur applications?

- Glenn W9IQ

Try to stay on track as this thread keeps bouncing around. A tubes life has nothing do do with this segment



Title: RE: Goodbye tubes.
Post by: KM1H on August 13, 2019, 06:23:42 PM
Quote
Yes.  It is almost certainly true just by the nature of the devices (tube vs. transistor wearout curves).  This is, in fact, a REALLY silly debate.  If Carl likes tubes and believes them to be the best, most reliable device family there is there is, so be it for him.  It's just "Carlworld", as usual.  No need to grid (sic) your teeth over it.

Brian - K6BRN

Grow up Brian or go away. When you have to resort to multiple insults in two posts you have already lost the argument and respect.


Title: RE: Goodbye tubes.
Post by: W9IQ on August 14, 2019, 03:21:59 AM
Try to stay on track as this thread keeps bouncing around. A tubes life has nothing do do with this segment

I am on track. You questioned the MTTF numbers for LDMOS. I am now questioning the comparative numbers for tube finals.

So answer the question - if you can. And don't forget to cite your sources. Come on Carl, getter done!

- Glenn W9IQ


Title: RE: Goodbye tubes.
Post by: K6BRN on August 14, 2019, 07:58:09 AM
Carl:
Carl (KM1H):

Thanks for your advice, but...

Quote
Grow up Brian or go away. When you have to resort to multiple insults in two posts you have already lost the argument and respect.

If growing up means becoming profoundly negative and calling just about everything and everyone around me "garbage" while insisting everything I have and do is far, far better that anyone else, I'll pass on that, thank you.  It's an old  cliche I never want to become.

Now... what was Glenn's question?  Tube MTBF vs. semiconductor MTBF?  There MUST be a quite a few good web-accessible examples to look at.  Mil-STD-217 would be a good place to start for tubes.  And for semiconductors, MIL-STD-883B is the place to go.  Then, once you understand the technology space, look for published papers on the topic.  Time to crack the books if you'd like to settle this debate in a factual way.

Best Regards,

Brian - K6BRN



Title: RE: Goodbye tubes.
Post by: KM1H on August 14, 2019, 08:04:59 AM
Quote
I am on track. You questioned the MTTF numbers for LDMOS. I am now questioning the comparative numbers for tube finals.

I did? Show me. Estimations dont count if that device hasnt been in service that long. Some call it a WAG since they know they wont be around to back it up.....for whatever reason.

Also show me the manufacturer published life specs of any of the common tubes used in amateur service today in commercial amps.

Carl


Title: RE: Goodbye tubes.
Post by: KM1H on August 14, 2019, 08:07:11 AM
Quote
Brian - K6BRN

IGNORE AS A CONTINUOUS HARASSMENT TROLL


Title: RE: Goodbye tubes.
Post by: W9IQ on August 14, 2019, 08:20:28 AM
Quote
I am on track. You questioned the MTTF numbers for LDMOS. I am now questioning the comparative numbers for tube finals.

I did? Show me. Estimations dont count if that device hasnt been in service that long. Some call it a WAG since they know they wont be around to back it up.....for whatever reason.

Also show me the manufacturer published life specs of any of the common tubes used in amateur service today in commercial amps.

Carl

Estimations? MTTF is a statistical representation. This would apply to both solid state devices and tubes.

I was deferring to you as the tube gray beard to supply the relevant MTTF numbers for continuous operation. As far as I know, they have never been published by the manufacturers.

- Glenn W9IQ


Title: RE: Goodbye tubes.
Post by: KM1H on August 14, 2019, 09:00:42 AM
Quote
Estimations? MTTF is a statistical representation. This would apply to both solid state devices and tubes.

It is still guesswork when it hasnt been verified no matter what fancy justification or name is used.

Quote
I was deferring to you as the tube gray beard to supply the relevant MTTF numbers for continuous operation. As far as I know, they have never been published by the manufacturers.

Well, you are wrong there as some TX tubes used in CCS broadcast service and some military apps were life rated.

Other small tubes used in non TX military gear had a MTBF rating for the complete unit where it was found that operating the equipment continuously produced the longest life.

Carl


Title: RE: Goodbye tubes.
Post by: W9IQ on August 14, 2019, 10:03:48 AM
It isn't guess work as much as accelerated life testing.

I still haven't seen any MTTF ratings for tubes that are commonly used in amateur radio linears. Can you quote or reference any?

We could extrapolate for some tubes where the life is dependent upon the cathode but I would rather see manufacturer numbers.

- Glenn W9IQ


Title: RE: Goodbye tubes.
Post by: W0BTU on August 14, 2019, 10:52:12 AM
Shame on you mean fellows for picking on gentleman Carl.   :)

On hamSE, that would absolutely not be tolerated! Right, Glenn?


Title: RE: Goodbye tubes.
Post by: K6BRN on August 14, 2019, 01:21:22 PM
Hi Michael (W0BTU):

Good to see you have a sense of humor, too.

Glenn (W9IQ), Carl (KM1H):

To help you out a bit, I went into MIL-HDBK-217E "Reliability Prediction for Electronic Equipment" and ran the numbers, just as a starting point.  It's on-line.  Anybody can download a copy and repeat the calculations below.

MIL-HDBK-217E has been around for decades and spans the tube, bipolar transistor, JFET and MOSFET eras.  For years, it was the "bible" of reliability prediction and was required reading for all trained electronics technicians in the Army, Navy, Air Force, etc. and also widely used in the Aerospace industry.  It is still referred to from time to time, even though better "initial estimate" methods exist today.

The handbook was written specifically as a "reliability made easy" starting point and standard reference, with its reliability coefficients drawn from extensive in-service life results collected over many years by industry and the government.  It's NOT the most accurate way to calculate reliability - but it gets designers "in the ballpark" very well, for the device classes it covers.

Since Carl is a former Navy radio tech, this SHOULD be a source he respects.  Since Glenn is heavily data and analysis driven, he should feel comfortable with this approach as well, AS A VERY ROUGH COMPARISON AND SANITY CHECK.

That said, I took the MRF-150 transistors in my Yaesu Quadra amplifier as the semiconductor to compare against - it has been the RF power MOSFET of choice in amateur radio solid state HF amps for decades and is very representative of a mature, well known device in wide amateur service.

Fot the tube HF high-power amplifier device, I chose the 572B/T160L in my SB-200, which has also been VERY popular in similar service for perhaps 50 years.  Even the power rating is comparable to the MRF-150.

Apples to apples.

Next, I assumed the very lowest grade of plastic MRF-150 transistor, running at a junction temperature of 100C, continuously (full power).  Continuous, max temperature operation is generally the worst-case for MOSFET transistor reliability and is VERY conservative compared to the occasional, intermittent duty cycles seen in amateur service.  So I stacked the deck against transistors.  A LOT!

For the 572B/T160L I assumed full power, continuous operation, with zero penalty for thermal shock and mechanical vibration - the Achilles heel of tubes, which is seen a LOT in amateur radio applications.  Continuous operation is where tubes are at their very best for in-service reliability.  So I zeroed out tow of their primary failure mechanisms and emphasized a key tube strength.  Every advantage to the tubes.

Doing the (very simple) arithmetic in the Handbook FOR THIS APPLICATION yields the following FIT rates (Failures In Time - per billion hours) - a lower number is better and MTTF is the reciprocal (in hours of the FIT rate):

MRF150 MOSFET transistor (worst case assumptions):  4,262 FITs
572B/T160L tube (under best case assumptions): 75,000 FITS


So, as a starting approximation, giving every advantage to the tube, the transistor is (very generally) at LEAST 18x more reliable than the tube.  Add in realistic thermal and mechanical shock derating for the tube and that difference reaches and exceeds 100x.  And, if you repeat the excercise, you'll discover that similar numbers can be produced for the for the 3-500Z, 3CX800, 1000, etc.

One note... I've found parts manufacturers data sheets to normally be more optimistic than MIL-HDBK-217, as you might expect, and their FIT rates are sometimes given only as a (much lower) base rate that need to be scaled up either by their own derating factors for use and environment, or by the factors given in MIL-HDBK-217.

Makes no difference, because in this excercise we are only interested in the approximate RATIO between tube and transistor reliability, for typical components used in amateur radio.  And our conclusion from this excercise is simply:  Transistors are (pretty obviously) WAY more reliable than tubes.

Big surprise.

Maybe it's time to debate something else?  Just a thought.

Best Regards,

Brian - K6BRN



Title: RE: Goodbye tubes.
Post by: KM1H on August 14, 2019, 03:01:45 PM
Brian, beside you wasting a lot of forum space who ever said that SS wasnt generally more reliable than tubes??? All I have done is point out exceptions and unproven guesstimates....which may be completely accurate, once enough hours have been reached.

It seems some of the desk bound types cant fathom this and their only defense is insults. Maybe management on here should step in on a few.

I have been familiar with MIL-HDBK-217E (whatever revision was current then) since the mid 60's thru decades later as a civilian tech thru engineer. Working on military projects it was a separate reliability group who was responsible.  Was that your job Brian since you seem to know so much about it?

I never worked on NASA projects and unlike some try not to post on subjects I do not have the familiarity with to make a meaningful reply....yet feel the obsession to blabber away anyway and often with misinformation that they will never admit to.

As far as the MRF-150 is concerned, the actual Motorola part as used in thousands of transceivers certainly had its share of failures without Hammy Hambone being involved as the cause. Many of those failures were unexplained by the manufacturers and the requirement to use only those that were matched within a fairly narrow bias range could be used. Maybe the Japanese didnt buy a copy of MIL-HDBK-217E.

The Japanese versions, 2SC2879, used by other companies, seemed to be more reliable except in CB amps ::)  Neither is readily available from a quality source (Fleabay is mostly Chinese counterfeits) and then the price soars. OTOH the 572B just keeps chugging along and even from China once they were pretty much forced into producing quality....their government does not like their legitimate companies such as Shuguang being seen in such a bad way and senior managers were often shot across many industries. Saving face is a big thing to the Chinese.

I never worked on NASA projects but I have worked on CIA projects ;D

As an ET in the USN MIL-HDBK-217xx was never mentioned except possibly as a reference in the manual. My job was to fix the gear and not look for things that were outside my rate description. The navy is funny that way ::)


Title: RE: Goodbye tubes.
Post by: KM1H on August 14, 2019, 03:05:41 PM
Quote
Shame on you mean fellows for picking on gentleman Carl.

Was that an insult Mike? I havent noticed any other comments from you in ages so wonder if you Trolled here. If so Im very disappointed as I thought you were above that low class stuff.

Carl


Title: RE: Goodbye tubes.
Post by: K4EMF on August 14, 2019, 03:29:53 PM
So.....now that we've settled that debate.   Anyone know where I can get a brand new 160m - 10m amp capable of a 100% duty cycle carrier for say less than $600?

Tube, solid state or even flux capacitor would be fine by me.


Title: RE: Goodbye tubes.
Post by: KD8MJR on August 14, 2019, 03:34:03 PM

Apples to apples.

Next, I assumed the very lowest grade of plastic MRF-150 transistor, running at a junction temperature of 100C, continuously (full power).  Continuous, max temperature operation is generally the worst-case for MOSFET transistor reliability and is VERY conservative compared to the occasional, intermittent duty cycles seen in amateur service.  So I stacked the deck against transistors.  A LOT!

For the 572B/T160L I assumed full power, continuous operation, with zero penalty for thermal shock and mechanical vibration - the Achilles heel of tubes, which is seen a LOT in amateur radio applications.  Continuous operation is where tubes are at their very best for in-service reliability.  So I zeroed out tow of their primary failure mechanisms and emphasized a key tube strength.  Every advantage to the tubes.

Doing the (very simple) arithmetic in the Handbook FOR THIS APPLICATION yields the following FIT rates (Failures In Time - per billion hours) - a lower number is better and MTTF is the reciprocal (in hours of the FIT rate):

MRF150 MOSFET transistor (worst case assumptions):  4,262 FITs
572B/T160L tube (under best case assumptions): 75,000 FITS


So, as a starting approximation, giving every advantage to the tube, the transistor is (very generally) at LEAST 18x more reliable than the tube.  Add in realistic thermal and mechanical shock derating for the tube and that difference reaches and exceeds 100x.  And, if you repeat the excercise, you'll discover that similar numbers can be produced for the for the 3-500Z, 3CX800, 1000, etc.

Brian - K6BRN

Yeah this would come as no shock to me.  I would say that even 100x more reliable in the real world is still a bit conservative.
For Ham Radio operations it might be around 50x more reliable because Hams treat their equipment well and by the nature of the Hobby they are not stressed by vibrations or other effects like a lot of power cycling.  It must have been a nightmare in the old days to use tubes on things like Planes and car radios.  I would imagine the failure rate was off the chart.  Of course that was before my time so maybe someone who was in the field back then can give me a history lesson on that.

73s
Rob




Title: RE: Goodbye tubes.
Post by: AA4PB on August 14, 2019, 04:18:13 PM
I worked on tube equipment used in the S2F aircraft back in the 1960's. You would think that carrier landings would be really hard on tubes but the majority of failures occurred when the equipment was first powered up, rather than during a landing. Originally they had a tech go out and power up all the avionics equipment (communications, navigation, and radar) several hours before the pilots manned the aircraft in order to check that everything was working okay. Later on they decided that most of the failures were occurring on power-up so they discontinued the early pre-flight check and just let the pilots check it on their preflight. If it worked for the pilot then it was not powered down again until the flight was finished. The overall failure rate was NOT improved by having the early check because it just added an extra power cycle so it was just as likely to fail the next time the pilot turned it on.

I was amazed to find that the S2F still had an ARC5 receiver. I was very familiar with them from my amateur radio experience during my teenage years (I purchased them new in the original carton for $10 each). It was nice to be able to replace the "bathtub" capacitors with the exact replacement from Navy stock instead of patching in a radial capacitor.  ;D


Title: RE: Goodbye tubes.
Post by: KD8MJR on August 14, 2019, 04:49:17 PM
I worked on tube equipment used in the S2F aircraft back in the 1960's. You would think that carrier landings would be really hard on tubes but the majority of failures occurred when the equipment was first powered up, rather than during a landing. Originally they had a tech go out and power up all the avionics equipment (communications, navigation, and radar) several hours before the pilots manned the aircraft in order to check that everything was working okay. Later on they decided that most of the failures were occurring on power-up so they discontinued the early pre-flight check and just let the pilots check it on their preflight. If it worked for the pilot then it was not powered down again until the flight was finished. The overall failure rate was NOT improved by having the early check because it just added an extra power cycle so it was just as likely to fail the next time the pilot turned it on.

I was amazed to find that the S2F still had an ARC5 receiver. I was very familiar with them from my amateur radio experience during my teenage years (I purchased them new in the original carton for $10 each). It was nice to be able to replace the "bathtub" capacitors with the exact replacement from Navy stock instead of patching in a radial capacitor.  ;D


Wow that is interesting.  So how bad was the overall failure rate for various modules.  Did they have to be replaced within a certain amount of hours or did they go by landings or what?  I assume that they would always chuck all the tubes during a service procedure.

73s
Rob


Title: RE: Goodbye tubes.
Post by: AA4PB on August 14, 2019, 05:25:09 PM
Wow that is interesting.  So how bad was the overall failure rate for various modules.  Did they have to be replaced within a certain amount of hours or did they go by landings or what?  I assume that they would always chuck all the tubes during a service procedure.

73s
Rob
Whenever the aircraft reached a certain number of operational hours (don't remember how many) then it was brought in for scheduled maintenance. We pulled all of the avionics equipment, brought it into the shop, and gave it a complete check to ensure that it met all original specifications. Tubes were only replaced if needed to bring the unit up to original specs. A detailed record was kept for each piece of equipment showing when it was in for repair and what was done to it. When the tech had the work finished, he had to get a QC guy to inspect it, recheck final specifications, and sign off on it before it went back into the aircraft. The failure rate really wasn't too bad but then the equipment was mounted on shock mounts with all mounting hardware safety wired. In addition, safety-of-flight equipment like radios and navigation stuff always had two independent systems in case one failed in flight.


Title: RE: Goodbye tubes.
Post by: KM1H on August 14, 2019, 05:32:58 PM
For Ham Radio operations it might be around 50x more reliable because Hams treat their equipment well and by the nature of the Hobby they are not stressed by vibrations or other effects like a lot of power cycling.  It must have been a nightmare in the old days to use tubes on things like Planes and car radios.  I would imagine the failure rate was off the chart.  Of course that was before my time so maybe someone who was in the field back then can give me a history lesson on that.

I have worked on tube equipment since 1955 when I started with a home brew regenerative RX and a 6AG7-6L6 TX for 80/40M.

Next came a BC-454 and 455 and it still continues thru 2019. I have been repairing/refurbishing radios for others and myself, including auto radios, since the mid 60's after being trained as a USN ET and later as a Service Tech at National Radio, one of the great names of the past.  

While I have plenty of modern gear including lots of SS up into the microwaves where I design and build much myself using state of the art components. While tubes provide most of the high power RF, up to 1500W, the ones for 1296 and 2304 MHz have been replaced by surplus commercial SS modules as the prices have plummeted; 903 MHz will be next. I doubt that anything lower in frequency will go SS since I have spares for all to last me in this life ;D

I also have a few operating benches dedicated to hollow state and used often on AM, SSB and CW.

I have found that auto tubes seem to last as long as any others since the types were common since 6.3V filaments became standard around 1932 for the new auto radio industry. Some real early glass tube types became microphonic in auto radios detector/first audio stage but you have to consider what passed for roads back then and vehicle suspensions were punishing even to humans. With the metal octal tubes debut in 1935 that problem went away except for replacing the old types which last just fine on modern roads.

Carl


Title: RE: Goodbye tubes.
Post by: KD8MJR on August 14, 2019, 06:14:48 PM
Wow that is interesting.  So how bad was the overall failure rate for various modules.  Did they have to be replaced within a certain amount of hours or did they go by landings or what?  I assume that they would always chuck all the tubes during a service procedure.

73s
Rob
Whenever the aircraft reached a certain number of operational hours (don't remember how many) then it was brought in for scheduled maintenance. We pulled all of the avionics equipment, brought it into the shop, and gave it a complete check to ensure that it met all original specifications. Tubes were only replaced if needed to bring the unit up to original specs. A detailed record was kept for each piece of equipment showing when it was in for repair and what was done to it. When the tech had the work finished, he had to get a QC guy to inspect it, recheck final specifications, and sign off on it before it went back into the aircraft. The failure rate really wasn't too bad but then the equipment was mounted on shock mounts with all mounting hardware safety wired. In addition, safety-of-flight equipment like radios and navigation stuff always had two independent systems in case one failed in flight.


Thanks for the history lesson :)  It's always nice to learn something from somebody who was there.
BTW I was watching a show on the Curiosity Stream about rebuilding WWII aircraft.  One thing that caught my attention during the episode on the P51D was that they mentioned that the engine was only designed for about 100 hours of flight time before it was literally dumped.  Although the guy said the odds of a pilot getting through 100 hours without something else  happening to the plane was pretty slim.


73s
Rob


Title: RE: Goodbye tubes.
Post by: KD8MJR on August 14, 2019, 06:23:35 PM

I have found that auto tubes seem to last as long as any others since the types were common since 6.3V filaments became standard around 1932 for the new auto radio industry. Some real early glass tube types became microphonic in auto radios detector/first audio stage but you have to consider what passed for roads back then and vehicle suspensions were punishing even to humans. With the metal octal tubes debut in 1935 that problem went away except for replacing the old types which last just fine on modern roads.

Carl

And here I was thinking that every time you dropped in a big pothole the radio probably went out  ;D
I guess if everything is constructed well it can take a fair amount of abuse before something cracks or gives way.

As for spare parts for the amps, I know what you mean.  I have a load of spare finals right now.   I just spent $400 on a pair of ARF1500 for my THP2.5Kfx.  The manufacturer says they are still being produced but I was not taking any chances.  I monitored Digikey and Mouser and saw the stock slowly going down from hundreds to just a handful. So I knew it was time to pull the trigger.  Now I have spares for every amp in the shack and shop. Plus a few extras of the cheaper stuff.

73s
Rob


Title: RE: Goodbye tubes.
Post by: W9IQ on August 14, 2019, 06:36:36 PM
For Ham Radio operations it might be around 50x more reliable...

I will take 50x as a defensible number. Now that the surviving posters are in violent agreement, can we move on?

- Glenn W9IQ


Title: RE: Goodbye tubes.
Post by: KM1H on August 14, 2019, 07:06:36 PM
Quote
And here I was thinking that every time you dropped in a big pothole the radio probably went out  Grin
I guess if everything is constructed well it can take a fair amount of abuse before something cracks or gives way.

Often it was the driver or passenger who went out ::)

Common damage in the 30's was wire wheel rims, tires/tubes, a bent front axle or wishbone in Fords. Independent front suspensions got their own share of damage.

With a lot of bodies framed in wood as late as 1935 those loosened up and added a lot of creaks and groans plus many roofs were tar covered cloth inserts as full body stamping/welding into one piece was playing catch up. Auto radio antennas had no common agreement; some were under a running board, in the cloth roof, attached to a rear spare tire ring, a little rod above the roof and turned by an inside knob, were among the most common. The cowl mounted telescoping antenna that most remember took over in the 1936-37 years and led by Philco

No, I wasnt around then but read a lot of auto industry magazines at libraries or what I picked up in the usual low cost places ;D

Quote
As for spare parts for the amps, I know what you mean.  I have a load of spare finals right now.   I just spent $400 on a pair of ARF1500 for my THP2.5Kfx.  The manufacturer says they are still being produced but I was not taking any chances.  I monitored Digikey and Mouser and saw the stock slowly going down from hundreds to just a handful. So I knew it was time to pull the trigger.  Now I have spares for every amp in the shack and shop. Plus a few extras of the cheaper stuff.

I stocked up when production volume was high and tube prices low. Most of my sealed box NOS came from hamfests, early Fleabay, estate sales and the like.  For awhile I was a mail order/hamfest reseller for CeCo in NYC of the popular Eimac tubes such as 3-400 and 500Z until Richardson screwed it up for everybody with a sole source agreement from Eimac. They also have all the original Cetron 572B tooling and are just sitting on it.

Carl


Title: RE: Goodbye tubes.
Post by: KM1H on August 15, 2019, 07:53:42 AM
Quote
I still haven't seen any MTTF ratings for tubes that are commonly used in amateur radio linears. Can you quote or reference any?

Since you enjoy sitting at a keyboard why not look for yourself?

Im going to take a nice long walk, get some Vitamin E, and then mow the lawn.


Title: RE: Goodbye tubes.
Post by: W9IQ on August 15, 2019, 08:02:58 AM
Since you enjoy sitting at a keyboard why not look for yourself?

Im going to take a nice long walk, get some Vitamin E, and then mow the lawn.

I did look rather extensively. Nothing found. I even read Bill Orr's "IVS" pontification but it appears that those ratings never took hold.

You are slacking, old man. I have already moved 80,000 pounds of hay and moved herds between pastures. My grass cutting involves 8 to 12 foot widths per pass. I am off tomorrow and Saturday so I should be able to get a lot more ranch chores done.

- Glenn W9IQ


Title: RE: Goodbye tubes.
Post by: K6BRN on August 15, 2019, 12:02:07 PM
This is getting too funny.  I'm checking in from a boat on Cayuga Lake.  Not mowing the lawn.  Not bailing hay or mucking out the barn.  I'm done with cattle, horses, ponies, chickens, peacocks, etc.  Did enough of that when I was young, working my aunts farm.  Right now, water is great, weather is great, concert tonight, play last night, great local food....   Life is good.  Will be moving on to QTH#2 on the Sound later this week. 

Concerning Carl's question... way earlier... just look me up on LinkedIn.  All you ever want to know is there or on line.  Degrees, patents, awards, papers.  Live it up and satisfy your curiosity.  No need to post it here.

On the tube vs. transistor reliability debate ... that's pretty much done.  Anything further is just beating a dead cow... um.  ...  horse.

Have a good week, gentlemen.  I'm going to cruise up to Taughannock Park now and see what's happening.  Boat is full of family and friends.

Brian - K6BRN



Title: RE: Goodbye tubes.
Post by: KM4AH on August 15, 2019, 01:28:24 PM
Now we can argue about whether or not you can discern the difference in the transmit audio quality of a transistor amplifier versus a tube amplifier.


Title: RE: Goodbye tubes.
Post by: KD8MJR on August 15, 2019, 03:45:47 PM
Now we can argue about whether or not you can discern the difference in the transmit audio quality of a transistor amplifier versus a tube amplifier.

Probably in AM or FM mode their might be a slight difference but I doubt in SSB that anyone could ever tell.
I have never seen any test done so I am just guessing.


Title: RE: Goodbye tubes.
Post by: K6BRN on August 15, 2019, 04:41:14 PM
Off topic triggered by Carl's old cars OT commentary....

Quote
With a lot of bodies framed in wood as late as 1935 those loosened up and added a lot of creaks and groans plus many roofs were tar covered cloth inserts as full body stamping/welding into one piece was playing catch up. 

The reason most "hard top" cars from the '20s and early '30s had flat, canvas covered  roof cutouts was to prevent annoying "oil-canning" when the body flexed.  It was not until the late '30s that makers realized that simply putting a gentle curve fore and aft and side to side in the steel roof would solve the problem.  No more canvas roof cutouts needed.

It had nothing to do with that eras metal stamping and forming technology, which was pretty good.

Brian - K6BRN


Title: RE: Goodbye tubes.
Post by: ZL1BBW on August 15, 2019, 08:19:10 PM
GENEROUS OFFER  ;D ;D ;D


Being as Toobes are so outdated, old fashioned, carbon hungry etc, as a kind hearted person if anyone has some good 3-1000's they wish to donate to me, I will plant some carbon absorbing trees on their behalf.

 ::)  Gavin  ZL1BBW


Title: RE: Goodbye tubes.
Post by: KM1H on August 16, 2019, 01:07:48 PM
Quote
The reason most "hard top" cars from the '20s and early '30s had flat, canvas covered  roof cutouts was to prevent annoying "oil-canning" when the body flexed.  It was not until the late '30s that makers realized that simply putting a gentle curve fore and aft and side to side in the steel roof would solve the problem.  No more canvas roof cutouts needed.

It had nothing to do with that eras metal stamping and forming technology, which was pretty good.

Brian - K6BRN

More misinformation here from Brian folks.

The well rounded and curved, called streamlining back then, 1934 Chrysler Airflow had a roof insert as did the the 1935 VW Beetle prototype, 1936 Toyota and Volvo that was inspired by Chrysler.

The insert remained due to production limitations until wide sheet handling metal drawing and stamping came along. Welding small individual pieces was costly and often came out warped. As bodies were slowly rounded the inserts shrunk in size. GM tested the public reaction to no insert in the 1933 Oldsmobile and the full line was all steel by 1936 as was Chrysler. Ford followed in 37.
The 1935 Chevrolet Standard had an insert and the Master was the first from GM to use the all new body.

Some luxury cars and coachbuilt models kept the insert a little longer as customers were often tradition bound.

Carl



Title: RE: Goodbye tubes.
Post by: W1BR on August 16, 2019, 03:08:13 PM
Now we can argue about whether or not you can discern the difference in the transmit audio quality of a transistor amplifier versus a tube amplifier.

Probably in AM or FM mode their might be a slight difference but I doubt in SSB that anyone could ever tell.
I have never seen any test done so I am just guessing.

FM mode????


Title: RE: Goodbye tubes.
Post by: K6AER on August 16, 2019, 04:21:53 PM
An amplifier does not have to be linear for FM.


Title: RE: Goodbye tubes.
Post by: KM1H on August 16, 2019, 05:20:30 PM
Nor for AM, CW, RTTY, SSTV, Digi.  Just for SSB and that can tolerate going rather deep into Class B before it becomes objectionable and there are ways to use it in Class E.


Title: RE: Goodbye tubes.
Post by: G3RZP on August 17, 2019, 02:34:20 AM
Quote
Nor for AM, CW, RTTY, SSTV, Digi

That depends on exactly what you mean by 'digi'. OFDM requires linearity, for example, while high order QAM has an appreciable amplitude component.


Title: RE: Goodbye tubes.
Post by: AH7I on August 17, 2019, 06:30:47 AM

The OP mentioned that he was looking to build a single band amp.  Why settle for single band, unless that's all you want.  The bandpass fillers are not hard to construct if you want multiband operation.
Solid state devices are here to stay, and they are in alot of applications better than tubes. 

But for some, nothing beats the glow of a tube.  And that's ok too.

The single band amp makes a lot of sense when using single band antennas.
No worries about band switching followed by antenna switching.
No worries about broadband transformers or broadband feed back.
With inexpensive active devices, for CW power on a few favorite bands, band specific or antenna specific amplifiers are more attractive for my application than spending $5k to $10k on an auto switching, auto tuning, idiot proof, computerized tube amp.

73 -Bob



Title: RE: Goodbye tubes.
Post by: KM1H on August 17, 2019, 08:23:06 AM
Quote
That depends on exactly what you mean by 'digi'. OFDM requires linearity, for example, while high order QAM has an appreciable amplitude component.

Im referring to the common ham band modes Peter. I had enough of that high level stuff at work where linearity specs for the multi channel TX was extreme. This was for Alcatel in the 23 -38 GHz segments for EU cell phone towers/poles. This was in the late 90's so Im sure the gear is more sophisticated these days.


Title: RE: Goodbye tubes.
Post by: K6BSU on August 17, 2019, 08:36:40 AM
The only place where "high fidelity" audio is even considered is 75M AM, where hams fo on for hours discussing audio quality.

Otherwise, the goal is audio "punch", where distortion is tolerated, and even encouraged in order to increase readablity.


Title: RE: Goodbye tubes.
Post by: W0BTU on August 17, 2019, 08:55:04 AM
I don't think that we are all on the same page.

Any mode that is generated in a transceiver and amplified by an external non-linear Class-C amplifier must have a steady carrier which never varies in amplitude, or IMD products will be transmitted with a resulting increase in bandwidth.

That includes CW and AM.

And I am not speaking of a class-C output stage where the plate is directly modulated by an audio amplifier in AM, nor a directly-keyed Class-C output stage which properly shapes the rise and fall times of a Morse transmission.


Title: RE: Goodbye tubes.
Post by: SM0AOM on August 17, 2019, 09:35:56 AM
Previously, some "hard statistics" about power tube reliability compared to transistors was requested.

Here is what I can come up with, from about 35 years of my own and others practice:

- Low and intermediate power tubes;
receiving and up to 6146 class, closely following the predictions in the tables of the "Reliability Engineering" textbook and the ARINC Report 411 "Investigation of Electron Tube Reliability in Commercial Airline Applications" a wear-out life of about 8000 to 13000 hours of H24 operations.

- Medium power tubes up to the 4CX250B/4CX350A class;
depending of usage profile, up to about 12000 hours when the tube quality was good such as in Eimac, ITT-STC and English Electric, but then declining to about 4000-5000 hours when "no-name" tubes came on the market.

8877s were used in about 20 AL-1500 amplifiers for maritime radiotelex channels during the time-period of 1993-2015.

Average tube life in the beginning around 12-15000 hours of H24 operation, later below 10000 hours but showed quite a lot of "outliers"

- Higher power tubes, P290A, 4CX5000A, 4CX10000D and 4CX15000A

The oxide cathode P290A, mostly around 18000-25000 hours in the beginning. Some late tubes went "gassy" already at
6-7000 hours averaging around 12000, but a select few survived for more than 80000 hours.

Without filament voltage management and reduction of idle current in SSB, 4CX5000As and 4CX10000Ds lasted for about 10000 hours in the 70s. When VOX relays and filament voltage management were introduced in the 80s, the life increased to about 12-14000 hours.

The original RS2793 (approx 4CX15000J) final in the Telefunken 30 kW amplifiers originally lasted for about 8000 hours, but after retrofit with 4CX15000A and VOX relays together with filament voltage reduction in the idle periods they lasted for about 13000 hours on average.

Now for transistors.

Smaller and early production power transistors in the BLX15 class, showed scattered ageing related (probably metal migration) failures after around 150000 hours of operation.
No definitive patterns were observed before finally retiring the transmitters in 2014, after a service life of over 30 years.
It appears that later production with ceramic cases had somewhat more stable characteristics.

Higher power transistors such as the ST TH430 and the 300 W Motorola type used in the Collins HF-80 and Spectrum 2000 system have not shown any systematic wear-out signs yet.

One system I am responsible for has been in H24 operations since 1996. It contains 6 Collins PA-2250 amplifiers (closely related to the HF-8023) each with 24 final transistors. Over 22 years of operations have netted 0 (zero) final transistor failures during about 27 million transistor-hours of operations.

Logged failures have been a few cases of worn-out electrolytics in DC-DC converters, and one (1) transistor failure in a driver amplifier,
possibly caused by a ripple-effect from a "blown-up" DC-DC converter.

Attempting to scale the field reported final transistor reliability to an amateur radio usage profile and to a typical amplifier design would point to a predicted MTTF of around 500 000 hours of H24 operations or 50 years.

However, it is likely that power supplies and other peripherals will have worn out before the final transistor MTTF is even approached.

The experience gained from using the smaller 8xBLX15 equipped amplifiers points in the direction that about 20 years of H24 operation is able to approach their MTTF.


Title: RE: Goodbye tubes.
Post by: G3RZP on August 17, 2019, 10:23:34 AM
Somewhat off topic, how do they protect the PA transistors from lightning induced EMP surges coming back down the transmission line?


Title: RE: Goodbye tubes.
Post by: SM0AOM on August 17, 2019, 11:03:11 AM
In the system I supervised, the amplifiers used DC-grounded combining networks and high-pass filters with static chokes between the antenna feedline entrance, switch matrix and the transmitters.

Also, Poly-Phaser transient suppressors using AC coupling were used at the amplifier output connectors, per the advice of the applications engineers at Rockwell-Collins when purchasing the PA-2250 amplifiers.

At the first location of the transmitters, one vertical log-periodic took a direct hit in the late 90s which damaged the balun and the transient suppressor without harming the PA transistors.


Title: RE: Goodbye tubes.
Post by: K6BRN on August 17, 2019, 11:17:55 AM
Karl-Arne (SM0AOM):

Well, your reliability input seem to be right in line with the MIL-HDBK-217 predictions of a transistor reliability edge of about 20x to 100x, depending on application and environment.  Nice to have yet another independent confirmation.

Brian - K6BRN


Title: RE: Goodbye tubes.
Post by: SM0AOM on August 17, 2019, 12:22:09 PM
Professional users have today for all practical purposes abandoned tube amplifiers due to operational economy, maintenance and reliability reasons.

An example;

During the final 5 years (44000 hours) of their operational life, the 6 Telefunken 20 kW amplifiers which usually were intermittently operated on the 5 kW level consumed a total of:

- 24 ea 4CX5000A
- 20 ea 4CX250B
- Other spares
- 300 man-hours of scheduled maintenance
- 150 man-hours of non-scheduled maintenance
- 1 500 000  kilowatt-hours of energy

totalling 1 300 000 SEK

Their Collins solid-state replacements consumed the following during their first 5 years

- 60 man-hours of scheduled maintenance
- 40 man-hours of non-scheduled maintenance
- 180 000  kilowatt-hours of energy

totalling 230 000 SEK


Also, it was possible to retire 2 engineers and technicians, and to de-man the transmitter site, only visiting it for a monthly maintenance check.

A financial analysis showed that the investment was paid off in less than 5 years, and that the operations using the transmitters otherwise would have to be prematurely curtailed when the site engineer retired or for lack of spare parts.

Radio amateurs seldom make financial analyses about their investments in amplifiers, but it may be of educational value to compare with enterprises that require profitability...


Title: RE: Goodbye tubes.
Post by: KM1H on August 17, 2019, 01:39:34 PM
Im glad to finally read some hard facts about properly operated commercial amps, presumably all HF or lower??

Now what about SS ham amps? Has anyone done a study and released the data??? Ameritron, Yaesu, etc?
What ham amp has used the failure prevention techniques as mentioned above?

Carl


Title: RE: Goodbye tubes.
Post by: K6BRN on August 17, 2019, 02:15:58 PM
Carl (KM1H):

Quote
Now what about SS ham amps? Has anyone done a study and released the data??? Ameritron, Yaesu, etc?

Odd question.  Why would you expect it to be substantially different? 

Because it's obviously not. 

There is still a thriving business in trading, buying/selling HF amplifier tubes as the existing stock shrinks and prices skyrocket.  They ARE consumables.  In amateur HF transistor amps, the final transistors are not considered consumable and usually have FIT rates as good or better than other amp components.  They do not often fail in a SS amp unless there is abuse, an amp design defect or infant mortality.

You saw the MIL-HDBK-217 numbers for the T160L/572B vs. MRF150.  You can run the numbers yourself for different parts, duty cycles, environments, device qualities, plastic vs. ceramic packages, frequency and use, etc.  It's just arithmetic.  Circle A and the various government tech corps took pains to make it simple and easy to use.
 And it has been used to set life and maintenence baselines for thousands of military and areospace systems for decades.   Oddly enough, quite a few off-the shelf amateur tranceivers, amps and receivers have also been used in the combined services for decades, as well as the agencies.

And assuming that all amateurs use their amps the same way is probably not a good bet.  If there IS an "average" amateur use for amps, it's probably "turned off 99.9% of the time".  Which means it'll be the caps that set the MTTF, not the transistors.

Now if you want a precise figure for, say a Yaesu Quadra MTTF or FIT rate in (composite) amateur service, perhaps you could call up Yaesu (or Elecraft, or Icom).  Chances are that they have done the calculations for their own equipment AND have service data available to back it up.  If you ask nicely, they may just tell you.  Then you can let us know.

Best Regards,

Brian - K6BRN




Title: RE: Goodbye tubes.
Post by: SM0AOM on August 17, 2019, 02:50:48 PM
The field reported MTTF:s and MIL-HDBK-217 figures for PA devices assume proper design and operation of the amplifier that contains the devices. If these criteria are not met, "all bets are off".

It appears that SS amplifiers that are aimed to the amateur markets are designed with smaller margins and with less elaborate protection than professional units in the same nominal power output range, which may lower the MTTF considerably due to catastrophic failures caused by overdrive spikes, self-oscillations or power supply transients.

In order to attain high fielded device MTTF figures, proper design and derating becomes very important.

Trying to get away with "ICAS ratings" for transistor currents and voltages will result in problems. Tubes are much more forgiving to momentary overloads caused by careless operation.

Frankly, the average amateur is not qualified to handle equipment that operates at power levels much above 100 W.
Very few understand the physical limitations for their equipment.


Title: RE: Goodbye tubes.
Post by: K6BRN on August 17, 2019, 06:26:17 PM
Mmmm.  Yes.  Amateur equipment design quality varies a lot.  From that of Elecraft KPA-500/KPA-1500 quality, where the amplifiers are very consevatively designed (and well done) to the marginal 3-tube MFJ/Ameritron ALS-800 amp design.

Regardless, all bets are off for ANY technology where designs are not properly executed.  Commercial, military or amateur.  And there are brainfarts in every category.

Brian - K6BRN


Title: RE: Goodbye tubes.
Post by: K6BRN on August 17, 2019, 06:39:06 PM
Regarding "ICAS"...  There is no such legitimate rating, in my mind.  ICAS WAS a RCA marketing rating aimed at the amateur market for tubes to convince them they could sacrifice tube life for power, when Tubes were pretty cheap.  And they could.  Today, when tube replacements are becoming more and more rare, it makes less sense.  It NEVER had any applicability outside of that realm.  Yet I see it attached to antennas, solid-state amps (and probably bananas) where it has no consistent basis or meaning.

It's like "Watts Music Playing Power" for stereo equipment of the '70's and '80s.  A stereo with a 1 amp fuse would claim "1,000 Watts MPP".  At least there, the FTC stepped in and clearly defined "Watts RMS" (no, its NOT literally the mathematical definition of RMS watts - two entirely different things), the test procedure and preconditioning period.  It was a reliable standard and apples to apples comparisons could be made across equipment from different makers.  It worked to bring claims to realistic levels.

Today, ICAS pretty much means "I THINK it'll work, for a very short while at least, at this power level.  Then it will probably catch fire or explode."

Brian - K6BRN


Title: RE: Goodbye tubes.
Post by: KM1H on August 17, 2019, 06:51:43 PM
Quote
The field reported MTTF:s and MIL-HDBK-217 figures for PA devices assume proper design and operation of the amplifier that contains the devices. If these criteria are not met, "all bets are off".

As anyone who has actually been involved would know.

Quote
It appears that SS amplifiers that are aimed to the amateur markets are designed with smaller margins and with less elaborate protection than professional units in the same nominal power output range, which may lower the MTTF considerably due to catastrophic failures caused by overdrive spikes, self-oscillations or power supply transients.

As to be expected and absolutely no surprise there despite some backround chattering.

Quote
In order to attain high fielded device MTTF figures, proper design and derating becomes very important.

Which costs money and that results in low sales at high prices. It should come as no surprise that Ameritron leads the pack in SS amp sales.

Quote
Trying to get away with "ICAS ratings" for transistor currents and voltages will result in problems. Tubes are much more forgiving to momentary overloads caused by careless operation.

Inadequate cooling is another SS problem in both home and mobile use.

Tube grid damage from momentary overloads has never been adequately examined AFIK. The typical ham is happy if the amp still works after it kicks off. To be clear Im talking about the 8873/74/75, 8877, 3CX800A7, 4CX1000A and similar 0-1W allowable grid dissipation tubes and not a 3-500Z, 3CX3000A7, etc.

Not mentioned by some of the anti tube chattering class is that several of the high power tubes in commercial service can be rebuilt several times at a substantial savings over new.

Quote
Frankly, the average amateur is not qualified to handle equipment that operates at power levels much above 100 W.
Very few understand the physical limitations for their equipment.

So true and so sad yet many of those are the first to claim they know all the answers and create OTA and online dissension with constant posting. IOW, they do not understand their own limitations, often between their ears.

Carl


Title: RE: Goodbye tubes.
Post by: W1VT on August 17, 2019, 07:41:29 PM
It appears that a lot of solid state TV amplifiers have outlived their useful lifetime with the re-arrangement of TV broadcast frequencies in the USA.  I just saw some ex-broadcast equipment this week!
After having to re-scan the channels on my TV set!


Title: RE: Goodbye tubes.
Post by: K6BRN on August 17, 2019, 08:16:21 PM
Quote
So true and so sad yet many of those are the first to claim they know all the answers and create OTA and online dissension with constant posting. IOW, they do not understand their own limitations, often between their ears.

Well... its an amateur forum for the radio amateur radio HOBBY and anything goes.  From those who know quite a bit to those who would like to learn (and more or less).  There should be no "pecking order here, just help and support.  At it's very best, ham radio is a service hobby - not just for amusement and emergency comms but also for help, enlightenment and goodwill to our fellow hams and citizens of the world.

It's not like the professional world where livelyhoods and lives are on the line, competence is absolutely required and reflected not in personal claims, but in professional college degrees, professional certification, high compensation levels, high demand for services, revenue bearing patents that allow early retirement, and where there are very real career ending disincentives for poor performance or the inability to work on a team.  Lots or real pressure in that realm.  For real reasons.

Apples and oranges, right?

Brian - K6BRN


Title: RE: Goodbye tubes.
Post by: SM0AOM on August 18, 2019, 01:32:46 AM
In properly designed and operated SS amplifiers for professional use, it appears that wear-out phenomena of other parts, such as power supplies, come much earlier than any PA transistor wear-out.

The SRT SSA400, that used BLX15 throughout in the driver and PA stages, was a very early (1973) SS amplifier, and had some "teething problems", with bias stability and device encapsulation. After correcting these, they have shown exceptional reliability.

The Danish Navy is into their third generation of exciters for these amplifiers (!), having worn out SRT CTD500 and
Selenia exciters during the 45 year usage term.

Failures due to electrolytic capacitor ageing and similar causes usually begin show up around 100000 hours of accumulated operating time.

Regarding the competence of radio amateurs, I am of the firm belief that amateur radio operators should be held at higher standards than professionals.

No professional operator is allowed to build or modify their equipment, and today's radio amateur has lower examination standards (with Germany as one exception) than the current maritime (GOC) or aeronautical radio operator.

An engineering degree and documented Morse competence should be required for the highest classes of amateur licences. Others should be limited to 50 W and "plastic radio equipment"


Title: RE: Goodbye tubes.
Post by: G3RZP on August 18, 2019, 02:28:17 AM
So from what Karl-Arne says, professionally, there are a lot of factors in the installation required to protect the SS amplifier against lightning induced EMP. That leads to my next question which is how many SS amplifiers fail in amateur service because of failures to provide such protection?

It seems to me unlikely that Joe Q. Ham will understand the protection requirements, and it's quite possible that an unexpected thunderstorm can occur with the amp switched off but still connected. I lost the front end FET in the FT102 in 1984 to a thunderstorm. I heard thunder as I got in from work, disconnected the VHF rig and there was a flash which was bright enough for me to seeing a purple afterglow for a few hundred milliseconds, a simultaneous loud bang that shook the house and the telephone answering machine started up , and required major repair to get it to work afterwards! That with underground telephone and electrical services....For my home brew amplifiers, I always had the antenna relay 'energise to receive', figuring that the PA tubes could stand the surge when off rather better than the receiver front end.


Title: RE: Goodbye tubes.
Post by: SM0AOM on August 18, 2019, 05:18:35 AM
It takes a "layered approach" to protect PA transistors (and receiver front-ends) from LEMP.

DC grounding and high-pass filters serve to bleed off the high-energy fundamental of the lightning waveform, transient protectors clip any voltage surges before they can make their way through the filtering.

SS amplifiers need more attention to detail in these matters, as the transistor junctions are more fragile.

The Poly-Phaser transient protectors we used clipped the transient waveform to about 500 V peak, and provided a first-order high-pass filter with about 500 kHz cut-off frequency.
 
The amplitude of a standard 4/20 µs lightning waveform would be reduced to about 100 V after passing through the network. Frequency responses of the combining networks would reduce it further before it can reach the transistors.

SSA400 amplifiers were connected via diplexers with an integrated matching network to large discones for MF maritime services, which used static drain chokes and the transmitters had transient protectors.

They attracted a lot of lightning, but no PA modules were lost during the 15 years they were in H24 operations, but strikes sometimes blew up mains fuses, SDSL data modems, intrusion alarms and ordinary telephone circuits at the sites.

Fitting proper entrance transient protections, mains line filters and using opto-isolation made the situation much better.

The SSA400s were retired in 2010, and strangely enough, their successors, 1 kW SS transmitters from "down under" were much more susceptible to lightning damage.

I did not work with these transmitters myself, but was told that transients entering through the mains feed was suspected to be the cause.




Title: RE: Goodbye tubes.
Post by: K6BRN on August 18, 2019, 07:52:51 AM
Quote
Regarding the competence of radio amateurs, I am of the firm belief that amateur radio operators should be held at higher standards than professionals.

You do realize that this is a hobby, it's specifically "amateur" radio, and the bands amateurs are authorized to TX on are miniscule.  In other words, any damage they may do is VERY limited.  For a reason.  It is literally a "playground"

Quote
An engineering degree and documented Morse competence should be required for the highest classes of amateur licences. Others should be limited to 50 W and "plastic radio equipment"

Morse code?  You MUST be kidding.  It has no purpose at all in modern communications.  Even POWs didn't use it to communicate between cells (they used "Tap Codes"). 

I guess I'd be fine (degrees, code certified).  But there'd be precious few people to talk to and the Hobby would be quite dead within a short time.

Maybe we just get along and help each other?  Joe Taylor and his digital communications develpment partner and team are literally setting the benchmark as we speak.  Maybe it's time to ask:  "What have I contributed?"

Best Regards,

Brian - K6BRN



Title: RE: Goodbye tubes.
Post by: SM0AOM on August 18, 2019, 08:08:06 AM
I am not kidding.

Morse qualified radio amateurs have shown to have much higher quality over the years than the "no-coders", which have wrecked our reputation with the regulators here.

They consider current amateur radio in general to be of low quality, being under-qualified in comparison to the privileges, and as a mostly irrelevant nuisance. If there was a simple way to reduce the number of radio amateurs to a more palatable level, the regulators would have implemented it long ago.

But in view of our irrelevance in the larger schemes of things, they are just waiting for the "attrition solution" of their problem.

And I am quite convinced that the views of the Swedish regulator are shared in more or less extent among the international spectrum management community.

In my opinion, the way of survival for amateur radio is along the path of quality before quantity, as we are supposed to form an elite among radio hobbyists.

We tried quantity, but it did not work.


Title: RE: Goodbye tubes.
Post by: G3RZP on August 18, 2019, 08:20:51 AM
I don't have a degree, Karl-Arne. But I can do Morse and I am a Senior Member of IEEE, with 16 now expired patents.  I have been paid to lecture to university short courses on RF, been a consultant to what was then the UK Dept of Trade and industry and a consultant in the RF field - including to a Swedish company. Degrees aren't everything.....My XYL has a licence, can do 18 wpm CW, has an honours degree in electrical and electronic engineering  and is a Chartered Engineer and MIET: her forte is in digital IC design, which isn't that applicable to RF problems.

Drawing up the ladder doesn't always help. What I find sad is the number of complaints of the shortage of RF engineers and yet amateur radio just isn't pushed as a way to get people into the field.


Title: RE: Goodbye tubes.
Post by: K4EMF on August 18, 2019, 08:48:29 AM
Morse code?  You MUST be kidding.  It has no purpose at all in modern communications.

You do realize that this is a hobby? Specifically "amateur" radio.  Based on my observations it would appear 10's of thousands of our fellow hams did not get your memo.
 
Quote
Even POWs didn't use it to communicate between cells (they used "Tap Codes"). 


Interesting, did they make up the code on sight or is this something they learned in survival school.   Do these "tap codes" survive today?


Title: RE: Goodbye tubes.
Post by: K6BSU on August 18, 2019, 09:15:37 AM
Proficiency in Morse has no relation to competence in electronics knowledge or proficiency. 

The so-called "dumbing-down" of amateur radio has more to blame than the elimination of Morse in licensing.  Instead, blame the written exams, which can be passed with only a marginal electronics knowledge.

I am an Extra class amateur (since 1952), with military Morse experience (35 WPM) and a BS in Electronics engineering. Yet, hands-on experience has taught me more about ham radio than any of my college classes.


Title: RE: Goodbye tubes.
Post by: SM0AOM on August 18, 2019, 09:22:45 AM
Drawing up the ladder doesn't always help. What I find sad is the number of complaints of the shortage of RF engineers and yet amateur radio just isn't pushed as a way to get people into the field.

So do I.

There is a major obstacle to find younger students that are interested in RF in general and HF in particular.

When trying to introduce grammar school pupils to amateur radio, they give "blank stares" back. Amateur radio lives up to its description of a "faintly embarrassing hobby" that it got in Time Magazine some decade ago.

The median age of newcomers here during the last year was about 55, and the fraction of "youngsters" around 10 %. "Yesteryear" their fraction was almost 40%.

But the major problem here has become the lack of quality, and the general "dumbing-down". People that have the patience to learn Morse, also have the patience to learn other subjects.

Earlier, amateur radio had a certain standing in the public eye, but during the last 20 years or so, the relevance of amateur radio has eroded considerably. We are now mostly considered as "weirdos".

This has not improved when certain elements started to pick fights with the regulators, leading to an almost complete distancing from amateur radio matters by them.
There will no longer be any support in the CEPT and ITU.


Title: RE: Goodbye tubes.
Post by: KM1H on August 18, 2019, 09:28:37 AM
Quote
I don't have a degree, Karl-Arne. But I can do Morse and I am a Senior Member of IEEE, with 16 now expired patents.  I have been paid to lecture to university short courses on RF, been a consultant to what was then the UK Dept of Trade and industry and a consultant in the RF field - including to a Swedish company. Degrees aren't everything.....My XYL has a licence, can do 18 wpm CW, has an honours degree in electrical and electronic engineering  and is a Chartered Engineer and MIET: her forte is in digital IC design, which isn't that applicable to RF problems.

What I find most disturbing are those who flaunt their degrees, patents, and "accomplishments" whenever some one questions their posting accuracy. To me that is an immediate Red Flag. Having a public biography easily visible gives the first level of weeding out the phoneys and poseurs and QRZ.com is the most often viewed site.

As an Engineering Manager and also Sr Engineer in an EE R&D group I found how easy it was for some job applicants to pass the generally useless HR weenies interviews, get past the also useless (Promote incompetence syndrome) hiring manager, and foist the results on needy group heads.

Ive dismissed outright or sent back upstairs to be moved to where "Do No Harm" slots were opened. Some of the worst were Piled Higher & Deepers who arrived fully arrogant, had no experience outside of academia, refused to take direction, had the group in an uproar and stunk to high heaven as the final insult :o. These were always from less than top rated engineering schools.

In academia and some companies the number of patents filed is part of the game and often means little in the end results.

Deadwood (dismissed without comments available) often wind up as consultants which really disturbs me as those who hire them have no business being in that position and the cycle continues.

Carl


Title: RE: Goodbye tubes.
Post by: K4EMF on August 18, 2019, 09:36:28 AM
I have not purchased an amplifier yet.   But I have been looking at what's available vs ham reviews and what not.

Given the large number of tube models still available.  I have surmised the reports of the death tubes have been greatly exaggerated.



Title: RE: Goodbye tubes.
Post by: N2SR on August 18, 2019, 10:45:42 AM
Proficiency in Morse has no relation to competence in electronics knowledge or proficiency. 

The so-called "dumbing-down" of amateur radio has more to blame than the elimination of Morse in licensing.  Instead, blame the written exams, which can be passed with only a marginal electronics knowledge.

I am an Extra class amateur (since 1952), with military Morse experience (35 WPM) and a BS in Electronics engineering. Yet, hands-on experience has taught me more about ham radio than any of my college classes.

So if the exams are "dumbed down," and with all that experience, you should be able to pass the Extra exam without studying one iota and get every question correct.  Please let us know when you plan to do that, and let us know what the result is. 


Title: RE: Goodbye tubes.
Post by: VK6HP on August 18, 2019, 11:49:23 AM
Karl-Arne (SM0AOM)

Thanks for an interesting commentary, including the opinion on licensing.  I share many of your sentiments although I don't believe that degree level qualification is the answer for two main reasons.  The positive one is that I have seen many motivated and intelligent hams, most usually qualified under earlier and stricter regimes, learn a great deal of solid RF theory and practice. Less positively, with a career in R&D and the real world, I've occasionally seen the irrelevance of formal education to good practice and even commonsense.  I do understand very well your comments about effective intake filters especially with national amateur bodies hopelessly conflicted between membership ambitions and standard setting, and national regulators being killed in the rush to abrogate their standard-setting duties.  It's certainly tempting to look for external filters such as formal qualifications and, in a weird way, the idea might indeed play to the current refrain of many western governments where, it seems, nothing is their "core responsibility" anymore and if something can be outsourced or privatised, they do so.

Unfortunately, outsourcing to conflicted bodies usually fails as most energy and resources get devoted to the bums on seats mission, at the expense of proficiency and standards.  Interestingly, I've also seen this in Australian recreational aviation, which is an almost exact parallel of the amateur radio case.  The difference is that the failings of the self-interested aviation administrating body, and the lazy and increasingly technically inept regulator, occasionally become all too publicly obvious as, for example, aircraft engines fail at more than an order of magnitude the established rate, or aircraft fly into ferris wheels, or....I could go on, but you get the point.

Fortunately, the failings of amateur radio standards are usually less severe, although they are certainly obvious to listeners and other operators.  They are pretty obvious on the internet forums, too.  For example, how is it that the US Extra class can admit folks who can run a 1.5 kW amplifier but have no clue how to hook up the keying circuit?  Why can a General licensee not do an Ohms Law calculation for filament voltage and current?  How do you get a licence without being able to work out the correct position of the antenna tuner relative to the exciter and amplifier?  OK, I'll again stop with the examples.

I wish I could say things were better in Australia, but they're not.  Reading a current discussion paper from the regulator (the ACMA) it's clear that they can't wait to shed any real responsibility for amateur radio as soon as possible.  It's goodbye to incentive licensing, and effectively open slather on bands and modes.  About the only thing they are worried about, in the fashion of the day, is whether hams cook themselves or anyone else with RF. One thing is sure: there won't be any serious national or international advocacy for ham radio forthcoming from them.

In my line of R&D I've actually been pretty successful in attracting very good RF and antenna people, including students, principally because of the challenges on offer.  A few of these people see the promise of ham radio as an experimental platform but, in truth, some are turned off by the lowest common denominator aspect of the hobby.  That tension has always been around of course but it seems to me that the top end of the hobby is now being invigorated at too low a rate.  About all I can think of as a counter-argument is that numbers are not the sole metric; it's who you attract and what they achieve.  That makes it worth continuing to try.

73, Peter.





 


Title: RE: Goodbye tubes.
Post by: SM0AOM on August 18, 2019, 12:32:39 PM
"It is difficult to predict, especially regarding the future"

The ACMA is probably as fed up with radio amateurs as are most other administrations, and you will end up in real trouble if and when they decide to "hand off" amateur radio matters to the power-hungry control freaks that run the national societies, preferably without transparency.

Some years ago, I became appointed to a working party that was tasked by the regulator to find ways to make the amateur radio examinations more in line with the intentions in the ITU Radio Regulations and the CEPT guidelines for competence.
This turned out to be an eye-opening experience.

From day one, the work was solidly obstructed by the national society that had one single objective; quantity over quality.

After a year and a half of continuous obstruction, including a smear campaign aimed at the official in charge intended to discredit him in the eyes of his superiors, the regulator finally lost patience, disbanded the working party and made up the new exams by themselves.

In a way the silent wishes of the regulator to reduce the number of radio amateurs may have been fulfilled, as the newly licensed numbers have dropped to an all-time-low.

The reasons for this are not clearly evident, but as amateur radio classes at the clubs often have to be cancelled due to lack of participants, a general lack of interest may be one of the main causes.

Back to the original topic.

The market for amateur radio amplifiers may be diminishing in general. Ageing population, EMC problems and a general lack of knowledge of how to operate and service an amplifier properly may contribute. Often, EMC problems with the neighbours start in earnest when the 200-300 W levels are reached. In countries like Germany, you also have to file a notice of EMF compliance with the Authorities, which may put off some prospective amplifier buyers.

Also, power tubes will only become more and more expensive for each year, as the markets are shrinking to just the "audiophools" and the older and older amateur radio users.

When the turning point will be is beyond my judgement, but as modern SS technology will become progressively cheaper, it is likely that we will achieve
a lower "watt per $" ratio for SS compared to the tube case within the next few years.

Younger radio amateurs are usually clueless of how to tune a "classic tube PA", which often results in them sitting unused in club stations. A friend of mine tried to teach proper tuning and loading practices to the preciously few 25-30 y/o that were present in his local club, but there were no interest. They simply did not want to learn.

If there will be any chance of selling amplfiers, regardless if they are tube or SS, to the few younger newcomers in amateur radio, the use of servo-tuning or automatic antenna matchers like our professional brethren started to use already in the 80s, or broad-band antennas likely will be required.

Any manual involvement of tuning and matching the antenna probably is way over the heads of the new-comers.





Title: RE: Goodbye tubes.
Post by: KM1H on August 18, 2019, 12:55:21 PM
Quote
Given the large number of tube models still available.  I have surmised the reports of the death tubes have been greatly exaggerated.

Wishful thinking from the chattering class.

If you dont want to learn how to service/update them as serious high voltage is involved there is likely someone close by that can help.

While some amplifier tubes will become unobtainium/very expensive there are very few if any that attract the audiophools. Adapting other tubes has been going on for decades.

Stay far away from sweep tube amps.

The Ameritron AL-811/811H have poor reliability due to overstressed tubes and engineering issues.

Carl


Title: RE: Goodbye tubes.
Post by: G3RZP on August 18, 2019, 02:08:47 PM
Karl-Arne and Peter,

It does appear to me that in my 20 odd years of dealing with Administrations at CEPT, iTU, the European Commission (probably the worst of the lot!) and ETSI that the dumbing down is by no means limited to the amateur radio world, but also to the technical ability of the majority of the younger people (<50 years old) in Administrations.

Which explains to some extent the apparent antipathy to amateur radio - a degree of jealousy that there are amateurs who are more technically competent that the so called porfessional administrators. Except when they want something, as was the case for 2012 Olympic games in London where they were appealing for suitably qualified amateurs to assist in checking gear being brought into the country.....


Title: RE: Goodbye tubes.
Post by: K6BRN on August 18, 2019, 05:12:25 PM
Hi Jay (K4EMF):

Quote
Morse code?  You MUST be kidding.  It has no purpose at all in modern communications.

You do realize that this is a hobby? Specifically "amateur" radio.  Based on my observations it would appear 10's of thousands of our fellow hams did not get your memo.

Yes, I do realize this is a hobby and (almost) anything goes in a hobby.  But it's not by any means modern communications.  More of an affectation to a commercially and militarily dead mode.  I get it, you like it.  But it's just not used in the "real" world anymore, for some very good reasons (there are MANY better modes).
 

Quote
Even POWs didn't use it to communicate between cells (they used "Tap Codes").

Interesting, did they make up the code on sight or is this something they learned in survival school.   Do these "tap codes" survive today?

Yes, tap codes live on.  See this for a basic background:  https://en.wikipedia.org/wiki/Tap_code

Hi Floyd (K6BSU):

Quote
The so-called "dumbing-down" of amateur radio has more to blame than the elimination of Morse in licensing.  Instead, blame the written exams, which can be passed with only a marginal electronics knowledge.  I am an Extra class amateur (since 1952), with military Morse experience (35 WPM) and a BS in Electronics engineering. Yet, hands-on experience has taught me more about ham radio than any of my college classes.

The current amateur radio exams are more excercises in memorization rather than in technology and were made that way as an attempt to breath new life into a dying hobby by opening the door to more amateurs.  Can't have it both ways, right now.  Way too much competition from other forms of amusement and technical hobbies.  Even high schools have turned away from amateur radio in favor of robotics, which seems more relevant to them today.  It's a pity, too.  Instant communications is what "makes our society go" right now.  But it's also killing ham radio.  If anybody has a good solution to this problem, let's hear it.  Because it would be SOOOO easy for the ITU to strip the really teeny/tiny ham bands aways from us - because to them, we have only nusiance value.

Regarding learning more in your career than in school...  I HOPE so!  An undergraduate degree teaches you the basics AND to a smart student demonstrates how much you will have to learn in the future, which is why its called a Bachelor's Degree (safe to practice without close supervision).  A 30+ year career will only add to fill out basic knowledge.  A Master's degree adds advance learning to that, and the title speaks for itself.  But without the Bachelor's degree and the basics, you really do not know what you do not know, and this is a very well known and major disadvantage in the workplace.

Hi Carl (KM1H):

Quote
What I find most disturbing are those who flaunt their degrees, patents, and "accomplishments" whenever some one questions their posting accuracy. To me that is an immediate Red Flag. Having a public biography easily visible gives the first level of weeding out the phoneys and poseurs and QRZ.com is the most often viewed site.

Actually, the most viewed professional site is LinkedIn, not QRZ, which is an amateur hobby site that no company offering a serious professional job really cares about.  And people who were unable to make the grade, do the work and actually get a degree from an accredited professional program at a university are usually the ones most resentful of those that actually have degrees and are successful.  And you are RIGHT in what you imply, that there are a number of very good non-degreed people doing engineering.  Don't hear much from them because they just do what they do and usually have to work 5x as hard to get ahead because they have not passed that very critical quality test of actually getting a degree.  They have to really, really prove themselves to any prospective employer and have a VERY hard time moving up.  The more motivated ones earn the degrees(s) they need to move forward, after work.  The ones that don't tend to stagnate.  There are always exceptions, but on the average, that's the way it is.

Regarding red flags - in a work environment, the inability to work on a team and contribute when and where needed without constantly putting down fellow workers is the primary red flag.

Hi Peter (G3RZP):

Quote
My XYL has a licence, can do 18 wpm CW, has an honours degree in electrical and electronic engineering  and is a Chartered Engineer and MIET: her forte is in digital IC design, which isn't that applicable to RF problems.

Sounds like one smart lady with a great earning potential.  Definitely a keeper!

Quote
It does appear to me that in my 20 odd years of dealing with Administrations at CEPT, iTU, the European Commission (probably the worst of the lot!) and ETSI that the dumbing down is by no means limited to the amateur radio world, but also to the technical ability of the majority of the younger people (<50 years old) in Administrations.

Newly graduating engineers from good programs in good schools are as good as they've ever been, IMHO.  I work with and mentor them every day.  However, the western business world has definitely decided to cut corners by placing unqualified, minimum wage personnel in improbable positions they are unqualified for, sometimes with comical or tragic results.  Data breaches are often driven by this.  Recent issues in the aircraft industry smell of this problem as well.

In addition, the venerable "5-year" plan for company, technology and product development seems to have been discarded in favor of A 1-year plan at many firms, leading to a crash and burn of their core technical competentcy, with GE being a reasonable example - as well as the previously mentioned aircraft businesses.  This is driven by the need to show a positive cash flow from technology and product development almost immediately, which means skipping much of the core engineering, testing and analysis that is required to produce a good, safe product.  Not a good trend at all and one we have to work hard to reverse.  In this, we are bucking the demands of major investment blocks (funds, money managers, etc.) whose decision cycles are now measured in milliseconds and spend less time looking ahead.  Not always, but very, very often.

Hmmm.  Think I'm caught up on this thread, now.

Best Regards,

Brian - K6BRN





Title: RE: Goodbye tubes.
Post by: K6AER on August 18, 2019, 05:49:58 PM
Morse code?  You MUST be kidding.  It has no purpose at all in modern communications.

You do realize that this is a hobby? Specifically "amateur" radio.  Based on my observations it would appear 10's of thousands of our fellow hams did not get your memo.
 
Quote
Even POWs didn't use it to communicate between cells (they used "Tap Codes").  


Interesting, did they make up the code on sight or is this something they learned in survival school.   Do these "tap codes" survive today?

Tap code is the rhythm of old-fashioned Morse code. I will bet 40% of the hams know CQ without a tone.

All pilots from WWII to current pilots are required to know Morse code. The VOR (VHF108-118 MHz.)  navigation aids are identified in Morse code. LAX, SFO, and my home airport CMA.


Title: RE: Goodbye tubes.
Post by: W9IQ on August 18, 2019, 06:25:30 PM
It is painfully clear that the younger generation is inferior, apathetic and inadequate. This has been known by generation after generation.

- Glenn W9IQ


Title: RE: Goodbye tubes.
Post by: K4EMF on August 18, 2019, 06:31:37 PM

Yes, I do realize this is a hobby and (almost) anything goes in a hobby.  But it's not by any means modern communications.  More of an affectation to a commercially and militarily dead mode.  I get it, you like it.  But it's just not used in the "real" world anymore, for some very good reasons (there are MANY better modes).


I get it, you don't like it.  As a hobby I guess I just don't see how what the military and or commercial operators use or don't use is particularly relevant to us.
 

Quote
Yes, tap codes live on.  See this for a basic background:  https://en.wikipedia.org/wiki/Tap_code

I have to admit I'd never even heard of tap codes.  Has anyone developed a new digital mode based on tap codes yet?  (sarcasm)


Title: RE: Goodbye tubes.
Post by: W0BTU on August 18, 2019, 07:00:33 PM
It is painfully clear that the younger generation is inferior, apathetic and inadequate. This has been known by generation after generation.

- Glenn W9IQ

LOL! ;-)


Title: RE: Goodbye tubes.
Post by: G3RZP on August 19, 2019, 01:40:13 AM
Brian said:

Quote
Sounds like one smart lady with a great earning potential.  Definitely a keeper!

Not now! She retired at age 58 - tired of the hassle of travelling the world, and also suffering 'managerial thrombosis'  -  i.e. having a manager who was a clot!


Title: RE: Goodbye tubes.
Post by: K6BRN on August 19, 2019, 05:46:54 AM
 Hi Jay  (K4EMF):

Quote
I get it, you don't like it.  As a hobby I guess I just don't see how what the military and or commercial operators use or don't use is particularly relevant to us.

Actually, I'm indifferent to CW as i rarely use it and enjoy digital modes more - my entire career has been based on digital comms and perhaps that's why.  Though I also enjoy a good rag=chew on SSB or AM.  I'm glad you enjoy using the code and more power to you.  But its purely a ham radio thing these days and perhaps one of the reasons hams are considered just a little eccentric by the general public (thought bubble of a 20-Y.O. standing next to a 60+ man with a straight key.)


Glenn (W9IQ):

Quote
Insert Quote
It is painfully clear that the younger generation is inferior, apathetic and inadequate. This has been known by generation after generation.   - Glenn W9IQ

OK!  Now (funny) irony!  You're doing a very credible impression of George Carlin!  I can see I'm going to have to "up my game" to compete at all in online humor.

Brian - K6BRN


Title: RE: Goodbye tubes.
Post by: K6BRN on August 19, 2019, 06:02:34 AM
Michael (K6AER):

Quote
Tap code is the rhythm of old-fashioned Morse code. I will bet 40% of the hams know CQ without a tone.

You're thinking of "American Morse Code". also known as "Railroad Morse".  Amateurs use "International Morse" and even the character construction is different.  Tap codes are a different animal entirely and are completely unrelated to morse code.

Quote
All pilots from WWII to current pilots are required to know Morse code. The VOR (VHF108-118 MHz.)  navigation aids are identified in Morse code. LAX, SFO, and my home airport CMA.

Maybe.  But one of my best buddies is a recently retired Continental pilot (retired during the merger) who has freely confessed he can't send/receive Morse code - just recognize a few sequences .  Rick had quite a chuckle about it when I asked him about it this AM.  Oh... and he's ex-Air Force.

Brian - K6BRN


Title: RE: Goodbye tubes.
Post by: VK6HP on August 19, 2019, 08:04:39 AM
Navaid morse is send veeeerrrryyyyy sloooowwwwwlllly...and even then most pilots refer to the cheat boxes written on the navigation charts.  Being able to read the ident without a chart is considered by fellow aviators to be one of my more useless skills :)


Title: RE: Goodbye tubes.
Post by: KM1H on August 19, 2019, 08:43:29 AM
Quote
When trying to introduce grammar school pupils to amateur radio, they give "blank stares" back. Amateur radio lives up to its description of a "faintly embarrassing hobby" that it got in Time Magazine some decade ago.

I didnt read that article but OTOH I would not have wasted money on that biased rag and only glanced thru it while in various waiting rooms.

I have mentored a few into the "hobby" but those were older Comcast CATV Service Techs who started with "What are all those antennas"?
All 3 are Extras and one is in love with CW.

Quote
From day one, the work was solidly obstructed by the national society that had one single objective; quantity over quality.

As does the ARRL where the name of the game is for employees/volunteers to stay in power forever. With only about 20% of FCC licensed hams ARRL members they are an embarrassment and not a resource.

Quote
The market for amateur radio amplifiers may be diminishing in general. Ageing population, EMC problems and a general lack of knowledge of how to operate and service an amplifier properly may contribute. Often, EMC problems with the neighbours start in earnest when the 200-300 W levels are reached. In countries like Germany, you also have to file a notice of EMF compliance with the Authorities, which may put off some prospective amplifier buyers.

I dont know about that. Amp companies come and go and at present they are at or near the highest numbers as several non US companies have become FCC certified. Those companies are far superior in quality and engineering than Ameritron.
Ameritron sales of the Big 3 amps are in the 100-200 per year range of each model but with a common platform including most components small common runs is profitable as the only big expense is tube choice.
OTOH their AL-811 and AL-80B family are widely popular. The AL-572B and AL-800's are odd choices which are seldom mentioned and I wasnt given their production numbers as I didnt ask ::)
The AL-811's exemplify the complete dumbing down of the modern ham and I cant think of a current analogy in the automotive world that would describe a Scheißkiste :o

Carl


Title: RE: Goodbye tubes.
Post by: K4EMF on August 19, 2019, 09:03:43 AM
...... Being able to read the ident without a chart is considered by fellow aviators to be one of my more useless skills :)

 8)


Title: RE: Goodbye tubes.
Post by: KM1H on August 19, 2019, 09:46:46 AM
Quote
Actually, the most viewed professional site is LinkedIn, not QRZ, which is an amateur hobby site that no company offering a serious professional job really cares about.  

Actually LinkedIn is of minimal interest to those in this discussion unless they are perpetually in search of a "professional" job for whatever reason.

Returning to Earth and this forum, QRZ.com offers a start in understanding who we are dealing with. Many continue to hide from that and after a prompt or two without a result I dismiss them as IMD distortion. ;D

Quote
And people who were unable to make the grade, do the work and actually get a degree from an accredited professional program at a university are usually the ones most resentful of those that actually have degrees and are successful.

Typical snob talk and far from reality in many cases. Many of those without degrees are often resentful of those that actually have them and are so poorly educated or suited for a real world environment that they cause project development to lag or even fail. Those individuals often show up on LinkedIn looking to save face as consultants.  Being a consultant saves companies a lot of money for multiple reasons plus they can be fired at will.

My reputation in the Boston RF world meant I never had to go begging for a job,  from Sr Tech to Sr Engineer, offers came to me on a regular basis. I also chose only those that were within a ~ 15- 20 minute commute.

Raytheon is one example of a company who has a long history of outsourcing jobs and even complete projects. In the past their treatment of employees caused unions to be formed right into the so called "professional" levels. It was/is a joke in the Boston area that everyone worked for Raytheon at some point. It is still a revolving door company.

An example is a company where I was a R&D engineer for millimeter wave products was hired by Raytheon to do all the RF development and interfacing to their digital electronics. They were a PITA to deal with as specs changed on the fly without discussion. I was in one meeting where one of their managers was berating us and I lit into him with both feet.
Trying to deal with union pukes in their engineering groups was just for starters. My manager was aghast but let me continue as I ticked off on my fingers what was really going on behind the scenes via many ham contacts which was a huge network in those days of the late 90's. Our company president nailed the Raytheon honcho at the top of that particular food chain, the a'hole that showed up was never seen again, and the project returned to a smooth process.  Likely the union honcho got a nice cash payoff to cooperate :o
I got a nice raise. ;D

Raytheon was also a raider and grabbed several of our test techs at a nice pay increase but being Raytheon they were gone when the end product was delivered. We did not rehire them.....

Carl


Title: RE: Goodbye tubes.
Post by: K6BSU on August 19, 2019, 09:54:19 AM
N2SR.  To answer your post.  I passed the Extra exam in 1955, after being a General for 3 years.  I did not have a "Study Guide".  I took the exam at the FCC Regional office in Los Angeles, and passed 20WPM Morse using pencil/paper and a straight key.

All this BEFORE entering college in 1957.


Title: RE: Goodbye tubes.
Post by: K6BRN on August 19, 2019, 11:10:37 AM
Carl:

Quote
Actually LinkedIn is of minimal interest to those in this discussion unless they are perpetually in search of a "professional" job for whatever reason

Um.  You mean like...  young, not yet retired and still working?  Exactly the type of people we need to continue the Amateur Radio hobby?  Kind of a "Let it die.  Who cares what happens after I'm gone" stance.  Hmmmm.

Well... there you go.

Brian - K6BRN


Title: RE: Goodbye tubes.
Post by: KM1H on August 19, 2019, 11:17:26 AM
Quote
Um.  You mean like...  young, not yet retired and still working?  Exactly the type of people we need to continue the Amateur Radio hobby?  Kind of a "Let it die.  Who cares what happens after I'm gone" stance.  Hmmmm.

Well... there you go.

Brian - K6BRN

A perfect example of fuzzy thinking with no links between them.
Par for the course.


Title: RE: Goodbye tubes.
Post by: K4EMF on August 19, 2019, 12:14:45 PM

....The AL-811's exemplify the complete dumbing down of the modern ham...
Carl

I'm always interested in experience based opinions.  Any elaboration you'd care to offer would be appreciated.

Jay


Title: RE: Goodbye tubes.
Post by: KM1H on August 19, 2019, 12:17:47 PM
Id suggest learning how to use the Search function on here and QRZ. Saves me time for other fun.



Title: RE: Goodbye tubes.
Post by: K4EMF on August 19, 2019, 01:33:40 PM
...All pilots from WWII to current pilots are required to know Morse code. The VOR (VHF108-118 MHz.)  navigation aids are identified in Morse code. LAX, SFO, and my home airport CMA.


You mean Military pilots?   I've been a professional civilian pilot for over 30 years and I've never been required to know Morse Code. 


Title: RE: Goodbye tubes.
Post by: K4EMF on August 19, 2019, 01:39:36 PM
Id suggest learning how to use the Search function on here and QRZ.



 Saves me time for other fun.

Of course, you could for example work on your second 5,000 posts.


Title: RE: Goodbye tubes.
Post by: KM1H on August 19, 2019, 02:52:19 PM
You should worry more about not falling out of the sky and learn more how to use the computer on your hobby time.
Most of my posts are trying to help others even when they are being "professional"........


Title: RE: Goodbye tubes.
Post by: SOFAR on August 19, 2019, 03:05:22 PM
Thats what ditches, streams and fields are meant for. The day I pay any fool bureaucrat/gummint entity  to dispose of something like that will never happen.

Carl

Helpful..


Title: RE: Goodbye tubes.
Post by: KM1H on August 19, 2019, 03:15:47 PM
Quote
Helpful..

Stale reply already discussed and you cant even attribute it to the proper thread........get a life.


Title: RE: Goodbye tubes.
Post by: W9IQ on August 19, 2019, 04:49:49 PM
Someone is in a snarky mood...

- Glenn W9IQ


Title: RE: Goodbye tubes.
Post by: KM1H on August 19, 2019, 05:38:08 PM
Quote
Someone is in a snarky mood...

- Glenn W9IQ

Id suggest staying out of something that isnt even thread related Glenn. it is called TROLLING.

The other person has nothing but insults for a comeback, Im sure neither one of us wants to be associated with anyone using a phony name either.

IGNORE TIME


Title: RE: Goodbye tubes.
Post by: K4EMF on August 19, 2019, 05:40:42 PM
You should worry more about not falling out of the sky
Fortunately for me between physics engineering and professional aeronautics it's of little concern.
Quote
... and learn more how to use the computer on your hobby time.
I'm was using it then when I asked for a simple explanation of your statement, and I am using it now.
Quote
Most of my posts are trying to help others even when they are being "professional"........

Would this constitute irony or...... hypocrisy?


Title: RE: Goodbye tubes.
Post by: KM1H on August 19, 2019, 06:13:28 PM
Quote
Most of my posts are trying to help others even when they are being "professional"........

Quote
Would this constitute irony or...... hypocrisy?

Straight Facts when viewed by someone without a self defeating agenda or personal vendetta.
I guess you dont qualify as a valid viewer.


Title: RE: Goodbye tubes.
Post by: K6BRN on August 19, 2019, 08:24:45 PM
OK. This thread has just become very painful for me.  I opened it up, read through the last few pages and laughed so hard I inhaled my "Dark & Stormy"  (a layer of dark rum over ginger beer) and blew it out my nose.  What a mess!  Still cleaning up...  OK...  OK...

A few choice one-liners from the posts....

To a pilot:
Quote
You should worry more about not falling out of the sky and learn more how to use the computer on your hobby time.

In response to a statement about safe electronic waste recycling...
Quote
Thats what ditches, streams and fields are meant for. The day I pay any fool bureaucrat/gummint entity  to dispose of something like that will never happen.
Anyone want to live in THAT neighborhood?

Quote
I have worked on CIA projects!
But of course!  All the best agents post their resumes on international forums.

Quote
And here is what ICAS is really all about from the horses mouth.
Wow!  I've heard the phrase "Know Thyself" but "Identify Thyself!" is REALLY above and beyond.

These lines read like Archie Bunker's script from a particularly crazy "All in the Family" episode.

Well, time to make another "Dark and Stormy".  Good night!

Brian - K6BRN





Title: RE: Goodbye tubes.
Post by: N2SR on August 20, 2019, 02:43:28 AM
k6bsu - what question did I ask you?   what I did say what that if you think the amateur radio tests are "dumbed down," then I challenge you to take and pass all of them today with no study guides and no prep.  please post the results of your exams.   



Title: RE: Goodbye tubes.
Post by: K4EMF on August 20, 2019, 06:09:36 AM
Do the bad actors on this website talk to their fellow hams on air with the same rude arrogant condescending tone they do online?

Is it any wonder FT8 is so popular?  Where there is no conversion.
If you despise people in general and polite conversations in particular.  What made you want to be a ham to begin with?