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Author Topic: solid state amplifier reliability  (Read 11227 times)
KC4ZGP
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Posts: 1276




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« Reply #30 on: April 18, 2017, 07:19:35 AM »


RR on the serious gear AC2RY. That's why I went with the EB-104 by Communications Concepts.

Say, you don't think MFJ is to hams what 'Great Value' is to the typical food stamp/welfare recipient
Wal-Mark shopper?
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KM1H
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Posts: 2188




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« Reply #31 on: April 18, 2017, 07:54:53 AM »

Ive found many items at WM that are equal to overpriced "national" brands. Just do your shopping the days before the welfare checks and EBT funds arrive.
I go there when I need a prescription filled and combine that with food shopping.

Recently even Harbor Freight has been improving quality.
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M0HCN
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Posts: 530




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« Reply #32 on: April 18, 2017, 09:08:23 AM »

Part of the problem is that folk will buy a 1kW amp, then notice that it has a MRF1K50 in there and decide that that means it must really be a 1.5kW amp, when the cooling, power supplies and filters are 'value engineered' to meet the 1kW level under ICAS operating conditions.

We are actually finally past the point where the LDMOS is no longer the major cost in a SS amp, so fitting power devices derated to 70% or even 50% of datasheet ratings is not anything like as expensive as it once was (That MRF1K50N is a $200 part from Mouser, probably much cheaper by the reel), and the derating is the key to reliability (Together with some PIN diodes or such to protect against overdrive, the other common way hams kill fet gates).
I await the release of the MRFX1K80N with interest, mostly for its higher drain voltage rating, cooling will still limit it to about a kW I suspect unless you go to water, but 180V abs max drain should improve robustness on a 50V or so rail significantly.

A set of three Taylor 572b from RFP or a 3-500Z will cost you about the same as the LDMOS device, and I bet the same guys that kill LDMOS gates slag tube grids in much the same way by doing much the same things.

If you operate a SSPA the same way you can get away with operating a glass fet amp, it will die, (the time constants are very much smaller), but it is not like an indirectly heated glass fet does not have its own issues if you do not know what you are doing.

The commercial stuff is reliable, the art will be in figuring out where the corners can be cut to produce an affordable product in the ICAS space (And no, cutting the protection circuits is NOT a good option, neither is designing for die temperatures above 200c), it may be that some rethinking of the relationship between the rig and the amp will be necessary to really make this work well, the commercial guys all come out of the exciter at mW levels, there is maybe a reason for this, it may be that an amp using the transverter connections to the rig actually makes better sense then one using the main output does.

Now MFJ reliability issues are of course nothing to do with SSPA reliability issues.

73 Dan.
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WA1RNE
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Posts: 986




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« Reply #33 on: April 18, 2017, 01:00:28 PM »

Quote
Why is it that I've never had a problem using a solid state transceiver while I had to send my ALS600 in for repair 7 times in less than a year?


 You might want to lead-in with the cause of failure for each of the 7 returns.

 Each may have been different or may not have been determined properly the first-second-third time, etc.  which puts a completely different spin on your question.

 
  ...WA1RNE

 
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N5PG
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Posts: 1011




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« Reply #34 on: April 18, 2017, 10:14:13 PM »

N0SQ,

I don't know how much 1955 (say) $200 or $250 is in todays $. But I suspect that todays ham who balks at whatever that is figures on getting more for less than hams did then. Maybe that is why more hams developed enough technical skill to build that which they couldn't afford to buy....

What cost $250 in 1955 would cost $2276.33 in 2016.
http://www.westegg.com/inflation/infl.cgi

73
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ZS5WC
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Posts: 609


WWW

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« Reply #35 on: April 20, 2017, 12:17:28 AM »

 :)Running IC-2KL going on 15 years since I have owned it .. Used it with rigs old and new, with or without overshoot, using alc and common sense. Never had an issue.
In tandem been running the EXPERT 1K-fa without a glitch for 3 years, reset bias of 6 Mosfets to my spec. Been running DX and local ragchews ever since.
Now with Expert 1.5K on horizon..Things are looking up!..

Nothing wrong with Solid state--you just have to apply some savvy and caution.
Problem with multiple FET devices is that the bias for all of them must be exactly the same, otherwise some work harder than others.

73 de William
ZS4L / ZS5WC
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N2RJ
Member

Posts: 1971




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« Reply #36 on: April 20, 2017, 10:23:26 AM »

Why is it that I've never had a problem using a solid state transceiver while I had to send my ALS600 in for repair 7 times in less than a year?

Have any of your solid state HF transceivers been made by MFJ? None of mine are either. They're either Kenwood, Yaesu, Icom or Flex.

I have a solid state amp in my shack and it works pretty well. However it is not MFJ.
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N2RJ
Member

Posts: 1971




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« Reply #37 on: April 20, 2017, 10:25:29 AM »

Part of the problem is that folk will buy a 1kW amp, then notice that it has a MRF1K50 in there and decide that that means it must really be a 1.5kW amp, when the cooling, power supplies and filters are 'value engineered' to meet the 1kW level under ICAS operating conditions.

If this is a dig at SPE, they advertise it as a 1.5kw amp. And quite frankly, I run mine at legal limit even on contest weekend without a problem, except on RTTY and high duty cycle digimodes. No complaints about the IMD and always get (unsolicited) compliments about a clean signal. I hear and see tons of dirty signals from overdriven tube amps and even from the 2K-FA which is a 2kw MOSFET amp.

The 1K-FA is a 1kw amp but it's not an LDMOS amp.
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W9FIB
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Posts: 2053




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« Reply #38 on: April 20, 2017, 02:12:46 PM »

Why is it that I've never had a problem using a solid state transceiver while I had to send my ALS600 in for repair 7 times in less than a year?

Have any of your solid state HF transceivers been made by MFJ? None of mine are either. They're either Kenwood, Yaesu, Icom or Flex.

I have a solid state amp in my shack and it works pretty well. However it is not MFJ.

So the MFJ91XXB series radios are tubes?

My MFJ amp works fine. It has for several years now.
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Happy being an Amateur Extra!
Nothing says CB on my printed license.
Ares/Races but no lights or crown vic.
AE5X
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Posts: 980




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« Reply #39 on: April 20, 2017, 04:13:16 PM »

I have a feeling that many Elecraft KPA-500's will be hitting the used market soon.....
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VK3BL
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« Reply #40 on: April 21, 2017, 04:33:39 AM »

Part of the problem is that folk will buy a 1kW amp, then notice that it has a MRF1K50 in there and decide that that means it must really be a 1.5kW amp, when the cooling, power supplies and filters are 'value engineered' to meet the 1kW level under ICAS operating conditions.

If this is a dig at SPE, they advertise it as a 1.5kw amp. And quite frankly, I run mine at legal limit even on contest weekend without a problem, except on RTTY and high duty cycle digimodes. No complaints about the IMD and always get (unsolicited) compliments about a clean signal. I hear and see tons of dirty signals from overdriven tube amps and even from the 2K-FA which is a 2kw MOSFET amp.

The 1K-FA is a 1kw amp but it's not an LDMOS amp.

A dirty signal report it always but one good propagation window away...  And I mean that with respect to all amplifiers, not yours specifically.  The 1K-FA is a very nice SS Amplifier by all accounts.
« Last Edit: April 21, 2017, 04:44:32 AM by VK3BL » Logged

J.D. Mitchell - VK3BL / XU7AGA - http://vk3bl.wordpress.com
KC4ZGP
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Posts: 1276




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« Reply #41 on: April 21, 2017, 05:32:37 AM »


RR Dave/ZS5WC.

Don't have to use everything available. My EB-104 is acclaimed at 600 watts but I'll treat her fairly and only go 400.

73 to everyone and wear your seat belt.

Kraus
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M0HCN
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Posts: 530




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« Reply #42 on: April 21, 2017, 09:29:22 AM »

No, not a dig at SPE, I don't own anything of theirs and will not comment on kit I have not played with, a dig at the golden screwdriver set!

Not that I would consider running a MRFE1K50 at 1.5kW to be good practise, because abs max is not a place on a datasheet you EVER want to be.

73 Dan.
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N2RJ
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Posts: 1971




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« Reply #43 on: April 21, 2017, 11:30:20 AM »

A dirty signal report it always but one good propagation window away...  And I mean that with respect to all amplifiers, not yours specifically.  The 1K-FA is a very nice SS Amplifier by all accounts.

I have one of the loudest signals in NA. If my amp was splattering you'd know it.
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N2RJ
Member

Posts: 1971




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« Reply #44 on: April 21, 2017, 11:32:03 AM »

No, not a dig at SPE, I don't own anything of theirs and will not comment on kit I have not played with, a dig at the golden screwdriver set!

Not that I would consider running a MRFE1K50 at 1.5kW to be good practise, because abs max is not a place on a datasheet you EVER want to be.

73 Dan.

Of all the critics of SPE and LDMOS amps, I have yet to see one person come up with actual measurements. All I ever hear is speculation. It is true that they are pushing it to the max, but so does nearly every ham tube amp, including popular designs based on 811A and 572B. These are also not your fragile MOSFETs of yesterday. This is new technology.
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