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Author Topic: Who likes a pair of MRF157?  (Read 15421 times)
VE7RF
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Posts: 212




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« Reply #30 on: December 29, 2011, 07:12:30 AM »

For a working project using a pair of these devices see http://www.ibelings.com/n4ip/mrf157.html

Note the size of the heatsink and the heat spreader because a KW amplifier is a serious piece of kit. FYI the current price of the MRF157 from Mouser is 610 Dollars per device.

Tanakasan

##  Yikes, that's $1220.00  for a pair of em !  I paid $1100.00  for a brand new Eiamac YC-243..[socketless version of a 3CX-6000A7].... which will do any easy 12 kw pep out..with superb IMD.  Heck, the smaller  3CX-3000A7  I have, will do an easy 5.2 kw pep out... with -59db  IMD3.  The 3CX-3000A7 tube is relatively cheap.  50w in=1.5 kw out   100w in = 2.5 kw out  150w in = 3.5 kw out.  200w in = 5.2 kw out.  the 3CX-3000A7 is one of the very best tubes for IMD  in the entire eimac catalog. 
None of these overpriced SS amps are all they are cracked up to be.  You trade "tune+ load"   for  "C1 + C2"  on the [now required]  KW rated  ant tuner.

later... Jim  VE7RF
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VE7RF
Member

Posts: 212




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« Reply #31 on: December 29, 2011, 07:17:18 AM »

Some of the RMI amps do use 28 volt devices and avoid the common 12 volt CB power devices...

Tom Rauch has tested at least one of those amps, and posted the results on his webpage. Concluding
remarks:

 



90 watts PEP: The HLA-150 is a 90-watt PEP amplifier at best, and if operated that way will be acceptable for many uses. It is not as good as it could be for the very wide bandwidth distortion at higher power, but it is comparable to worse-case IMD for a common radio like the FT1000MP when it is at 90-watts PEP output.


The HL150 amplifier has exceptionally good harmonic suppression on most bands. The low-pass filters work well. It is an acceptable amplifier when operated at 90 watts PEP output or less.

 


It appears that running these amps conservatively might indeed improve IMD.  It is pretty sad to see the IMD can even be
compared to the typical IMD of what is a very popular transceiver.

Personally, if someone gave me one I'd consider using it after a 10 watt K2 or K3 on CW providing the harmonic suppression
meet FCC spec.

Pete
[/quote

##  well, u almost got it right.  RM  rates that amp at an absurd 300w pep out.  The devices used in it are only RATED at 150w pep out max..and that's with lousy IMD.  JI is right, if u back it down to 90 w pep out, it's IMD is now acceptable...barely.  No way , shape or form is it good for 300w pep out.  But at 90w pep out, it's eff is beyond lousy.

Later... Jim  VE7RF
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M0HCN
Member

Posts: 473




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« Reply #32 on: December 29, 2011, 07:34:28 AM »

And you can not run the amp at less than 400w!  The eff is so low at  that power level, that it kicks itself offline.
Cannot be true surely, with SSB a 1KW amp will spend most of its time well below 400W.
Efficiency does go down at less then 100% power as the drain match degrades, but I cannot see any linear amp being designed to drop off line under those conditions, I could maybe see it in a class C or E design where the heatsinking would not cope with the dissipation caused by inadequate gate drive, but not in a 'linear'.

There is of course no doubt that RM basically make for the 11M market, with some spin off into ham markets, and little doubt that the ah "Value Engineering" is somewhat more extreme then I would be happy to perpetrate, but I will again withhold judgment until some real numbers for that particular implementation become available. There is more to this subject then the data sheet numbers, which in any case are often just given for third order.  

Not all countries have this weird CB/HAM pissing match going on, and most actually do not have a major issue with numpties with KW class CBs.... That is a peculiarly US thing, and while I do not much like the look of RMs stuff, and would probably buy something better if I was in the market, I am not prepared to publicly slate a product I have not even seen a final data sheet for let alone had on the bench. The US has all sorts of regs aimed at their 'CB problem' that do not apply elsewhere, and actually I can see uses for a low drive power PA that are entirely legitimate (Saves a couple of stages when building a rig).

My old Racal TA1816 solid state amp will make full output all the way across the HF spectrum with just 250mW drive, and that is not a pony piece of kit by any means. If you have the space and are satisfied with 500W from a rather old design they are also a bargain (£250 region), and we are limited to (for a full license) no more then 400W at the feed point anyway.

I would note that Italy has for a long time had a somewhat 'relaxed' attitude to such things as the more inconvenient European Directives on things like electromagnetic compatibility, and has also been a long time producer of very cheap (and generally not much loved) radio transmission gear.

Regards, Dan.
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K1ZJH
Member

Posts: 949




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« Reply #33 on: December 29, 2011, 08:40:05 AM »

 

 
 

 Personally, if someone gave me one I'd consider using it after a 10 watt K2 or K3 on CW providing the harmonic suppression
meet FCC spec.

Pete

##  well, u almost got it right.  RM  rates that amp at an absurd 300w pep out.  The devices used in it are only RATED at 150w pep out max..and that's with lousy IMD.  JI is right, if u back it down to 90 w pep out, it's IMD is now acceptable...barely.  No way , shape or form is it good for 300w pep out.  But at 90w pep out, it's eff is beyond lousy.

Later... Jim  VE7RF

Jim

I never realized the IMD was a consideration on CW....  Grin Reread my post.
With some harmonic filtering many of the "CB" amps might have some utility for giving a CW QRP rigs a boost of several dB..
Of course, that assumes they are found at bargain prices, and the design offers something to work with to start with.
I'd jhope that any competent ham can add harmonic band filters as needed.
Pete
« Last Edit: December 29, 2011, 08:58:01 AM by K1ZJH » Logged
W5JON
Member

Posts: 163




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« Reply #34 on: December 29, 2011, 12:22:07 PM »

Quote Zenki:
DNJ Radio another illegal seller of CB amplifiers most of which end up on the US market.  I wonder when the FCC will close them down? OH I forgot its for export only!

1. To be accurate your statement should say: DNJ Radio another illegal seller IN THE US, BUT LEGAL IN THE REST OF THE WORLD of CB amplifiers most of which end up on the US market.  I wonder when the FCC will close them down? OH I forgot its for export only!

2. "I wonder when the FCC will close them down?" If the FCC standards are to be enforced on foreign companies to meet US IMD standards, when will FCC make it ILLEGAL for US Amp manufactures to produce or sell amps capable of 2kw, 3kw, 4kw that are ILLEGAL on the amateur bands in the US AND THE WHOLE REST OF THE WORLD.  In your words: OH I forgot its for export only!
So please be accurate RMI amps are Illegal in the US, BUT LEGAL IN THE WHOLE REST OF THE WORLD, unlike 2kw+ amps.

3. When will the FCC not allow the US tranceiver manufactures to sell tranceivers in the US that can transmit PHONE in the US CW portion of an amateur band, against FCC rules.

These are only a couple of examples, there are MANY.

I am not condoning the problems of the RMI products, for all the reasons beat to death in this forum.  HOWEVER, it would be a very slippery slope, when a country trys to force its standards, rules, laws on the rest of the world.  The IMD slope being amoung the most slippery.

73,

John  W5JON

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N3OX
Member

Posts: 8854


WWW

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« Reply #35 on: December 29, 2011, 05:01:46 PM »

I never realized the IMD was a consideration on CW....  Grin

Depending on the transfer function of the amp, it can make a CW signal more clicky.  

I built a cheap 400W MOSFET amp for 160m using ordinary power MOSFETS.  (http://n3ox.net/files/uglyamp/inside_annotated.jpg)

I was running a few hundred mA bias.    It plus the exciter had pretty bad IMD even at 350W, something like 17dB below 1 tone (I never used it on SSB only on CW... I was just curious):

http://n3ox.net/files/350W_2tone.jpg

That's an audio 2 tone test of the full chain, FT-857D + amp, but I did the '857D at amp-drive level (7W) and it was more like 27dB down on the left hand 3rd order product (don't know what's up with the asymmetry... yikes)

Bunch of other junk in there is some kind of noise problem I believe, though some of it seems to be in the exciter output too at different levels... anyway, this was a very simple lashup, mixer into soundcard like this:

http://www.astromag.co.uk/ssa/

I also measured the spectrum with 20WPM dit string:

http://n3ox.net/files/400W_uglyamp_20WPM_widest.jpg

500Hz away I was down a bit less than 40dB.  That's not great, compare to the K3 keying spectrum on G4AON's page where it's 60dB down at 500Hz away.   I believe the K3 is generally considered excellent in the click department.   Now, that relatively bad spectrum is NOT the amp's fault entirely or even the majority.  Mostly it was my exciter.  But when I measured compared to the exciter spectrum the amp made it about 3dB-4dB worse out in the tails.  A few dB probably isn't a huge deal but it is what it is.  Switching to a better rig or fixing my keying would  have made more of an improvement in my total spectrum occupancy but the amp did make it a little worse.  

I don't remember now how close 400W was to running it saturated, and I can't check it without replacing the FETs Cheesy
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73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
ZENKI
Member

Posts: 916




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« Reply #36 on: December 29, 2011, 06:21:21 PM »

Hi Jon

Well wherever the CB service is legal in a proper western democracy, high power CB amplifiers are illegal. These amplifiers  are illegal in most of Europe. SSB has only just become legal in Europe and the legal limit will be 12 watts pep. Not 200 watts running a RM Italy product. Just as you can buy illegal CB amplifiers from this company in the USA, you can also buy these products everywhere else in the world. This still makes them illegal products in most countries where the CB service is legal.

If you want too understand the impact of this uncontrolled marketing of illegal CB radios, handhelds and HF equipment, just take a trip down too somewhere in Asia. From one end of the spectrum to the other, including critical frequencies like Air and  Marine rescue, the bands are all full of pirates. The HF aeronautical channels are also full of pirates running illegal amplifiers and  using them as CB chat channels. Theses pirates are causing havoc and endangering the public's safety. This is even before we start talking about the ham bands like 10 and 12 meters that is covered by stations using these illegal radios and amplifiers. Many of these radios are the ones that the so called CB hams want to promote here as legitimate ham equipment. We only supporting piracy by making these companies successful.

How any ham can support these products and not be concerned about the long term implications of  having too share the spectrum with illegal cbérs is beyond me. Their products are really part of the cancer, and this cancer is spreading to the ham bands. Hams who should know better who think that  using these products  are really making a fundamental technical mistake in their judgement. Its just unfortunate that many dont even understand the implications  of their poor decision making.

The long term destruction of the HF frequencies by turning the spectrum into a no mans  wasteland will be our demise too as a ham service. Politicians need every excuse possible now to try and destroy the HF services for things like BPL. Us becoming anarchists and ignoring the law will only hasten our own demise. Practices like splattering the band by using poor CB amplifiers will only enhance the arguments for increasing emission limits from things like BPL. Unfortunately the fools who use these products dont even understand how they are contributing to the destruction of the weak signal noise floor of the higher frequency bands.

While the FCC might not have a legal right enforcing  sales of CB amplifiers internationally, they do have an obligation under international law too stop the illegal use of the HF spectrum in all its forms. This would include suppliers of equipment that is shipped from the shores of the USA, especially when the equipment is destined to be used by illegal pirates.  If you are breaking ITU regulations the FCC could technically pursue you. I wont pass any further comment since I am not familiar with the the FCC laws, and how the apply internationally to their obligations too enforce ITU regulations. I will stick with attacking the scourge of filthy amplifiers that seem to be drifting into the ham bands. Nasty filthy pollution that no ham really needs to put up with because of idiots

Giving any of these companies support in anyway is only hurting our own long term interest..

Quote author=W5JON link=topic=79840.msg564556#msg564556 date=1325190127]
Quote Zenki:
DNJ Radio another illegal seller of CB amplifiers most of which end up on the US market.  I wonder when the FCC will close them down? OH I forgot its for export only!

1. To be accurate your statement should say: DNJ Radio another illegal seller IN THE US, BUT LEGAL IN THE REST OF THE WORLD of CB amplifiers most of which end up on the US market.  I wonder when the FCC will close them down? OH I forgot its for export only!

2. "I wonder when the FCC will close them down?" If the FCC standards are to be enforced on foreign companies to meet US IMD standards, when will FCC make it ILLEGAL for US Amp manufactures to produce or sell amps capable of 2kw, 3kw, 4kw that are ILLEGAL on the amateur bands in the US AND THE WHOLE REST OF THE WORLD.  In your words: OH I forgot its for export only!
So please be accurate RMI amps are Illegal in the US, BUT LEGAL IN THE WHOLE REST OF THE WORLD, unlike 2kw+ amps.

3. When will the FCC not allow the US tranceiver manufactures to sell tranceivers in the US that can transmit PHONE in the US CW portion of an amateur band, against FCC rules.

These are only a couple of examples, there are MANY.

I am not condoning the problems of the RMI products, for all the reasons beat to death in this forum.  HOWEVER, it would be a very slippery slope, when a country trys to force its standards, rules, laws on the rest of the world.  The IMD slope being amoung the most slippery.

73,

John  W5JON


[/quote]
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M0HCN
Member

Posts: 473




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« Reply #37 on: December 29, 2011, 06:59:59 PM »

I would like a cite on SSB CB being legal in Europe, as far as I can see everything on 11M over here is FM (And the CB band is basically dead on a quick tune around).

CB enjoyed a brief period of popularity in the early to mid  80's, but has largely died, killed by the mobile phone.
In fact it was noticeable that ham radio actually got a lot of converts from CB at the time (Including G0FUW the guy who put our exam course manuals together!), it really was not a bad thing for amateur radio over here. 

I still say KW class CBs are a mostly US problem, and it is noticeable that while a 11M KW class C 'linear' may be illegal to USE, the US is about the only place that requires amplifiers to add hardware to explicitly lock out the 11M band in order for them to be legal to SELL.
Hell a CB and crap 11M amp probably makes a dandy RF source for a plasma generator or a AO Q switch or something, and as long as it does not radiate, wheres the problem?

I suspect you are projecting US problems and to some extent cultural assumptions onto places where it does not apply.

Regards, Dan.
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K1ZJH
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Posts: 949




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« Reply #38 on: December 29, 2011, 07:03:11 PM »

We have our own crap being sold over here, and the RM amps actually put them to shame!!!!

http://fatboyamp.com/

Note that "biasing" is an extra option!  No warranty for blown "pills" or alcohol related problems Smiley

Pete
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M0HCN
Member

Posts: 473




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« Reply #39 on: December 29, 2011, 07:16:11 PM »

I had thought I was joking about a class C 'linear'! OUCH!
I take it 'Pill' is CB speak for transistor? 

PLEASE tell me that stuff is purely aimed at the 11M market.

Regards, Dan.
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K1ZJH
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Posts: 949




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« Reply #40 on: December 29, 2011, 07:25:44 PM »

I hope so. Apparently the FCC turns a blind eye to this; those amps are even sold on eBay!
There's a few other equally bad vendors, but they try to skirt the law by selling "kits" stateside.
Yes, pill apparently is CB slang for RF power transistors.  Unfortunately, I'd bet more than a few
of these are on the ham bands. 48  each 2SC2879  devices to make a claimed 12,000 watt PEP
(fairy tale type watts) amp that runs on 12 volts!!!!!!!!!!!!!

Pete
« Last Edit: December 29, 2011, 07:35:31 PM by K1ZJH » Logged
VE7RF
Member

Posts: 212




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« Reply #41 on: December 30, 2011, 06:03:55 AM »

I hope so. Apparently the FCC turns a blind eye to this; those amps are even sold on eBay!
There's a few other equally bad vendors, but they try to skirt the law by selling "kits" stateside.
Yes, pill apparently is CB slang for RF power transistors.  Unfortunately, I'd bet more than a few
of these are on the ham bands. 48  each 2SC2879  devices to make a claimed 12,000 watt PEP
(fairy tale type watts) amp that runs on 12 volts!!!!!!!!!!!!!

Pete

### believe it.  Did u browse the fat boy site?   Check out their bird/coaxial dynamics page. They have slugs  right up to 100 kw. I wonder if they even include the LP filter on their amps ?   If not, the harmonic content would be absurd.  And any wattmeter will be reading way higher than normal..which is probably part of the scam.  [Ameritron  says with an LP filter installed, after the combiners, you could see as much as a 40% drop on a wattmeter. Ameritron sells a stand alone box, with several 1 kw pep rated /400W CCS LP filters in it]

##  check their wattmeters.. fat boy style  http://fatboyamp.com/...under "bird supplies"  They also seem to have developing the power figured out..and run em up to 20 vdc. ..using motor mauls and dahl xfmr's etc.

later... Jim  VE7RF
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ZENKI
Member

Posts: 916




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« Reply #42 on: December 30, 2011, 06:05:37 PM »

If we used ham power ratings, the  12000 watt 48 device amplifier is really only a 2400 watt amp. Then if you wanted it to clean you would have to half that power again  for real power output of 1200 watts. 

What I find interesting is that they have all this mega hardware on their web page, however the only dummy load that they can come up with is a lousy 1kw  cantenna. It says a lot about their hyperbola associated with their amplifiers output power.

A pair of 2SC2879s is  really only good for only 50 watts of clean power. Ham transceivers typically  run them up to 100 watts of output. The idiots screw their radios above this.

I would rather have a 200 ft tower with  6 stacked Ultrabeam antennas which  can be electrically steered, an antenna like this would accomplish something with 100 watts of output power.  Unlike these idiots whose only legacy will be causing a lot of interference. I find it staggering that they dont have multiple brain tumors from being exposed to such high RF fields. 27mhz is a common industrial heating and MRI frequency. Hey, if they having fun so be it, just keep this garbage away from the ham bands! Its a living nightmare if you  have a Cbér who runs illegal power and lives near you. Even a W3NQN bandpass filter cant stop the trash from breaking through on and 10 and 12 meters. The only re-course is a call to the local authorities.

I hope so. Apparently the FCC turns a blind eye to this; those amps are even sold on eBay!
There's a few other equally bad vendors, but they try to skirt the law by selling "kits" stateside.
Yes, pill apparently is CB slang for RF power transistors.  Unfortunately, I'd bet more than a few
of these are on the ham bands. 48  each 2SC2879  devices to make a claimed 12,000 watt PEP
(fairy tale type watts) amp that runs on 12 volts!!!!!!!!!!!!!

Pete

### believe it.  Did u browse the fat boy site?   Check out their bird/coaxial dynamics page. They have slugs  right up to 100 kw. I wonder if they even include the LP filter on their amps ?   If not, the harmonic content would be absurd.  And any wattmeter will be reading way higher than normal..which is probably part of the scam.  [Ameritron  says with an LP filter installed, after the combiners, you could see as much as a 40% drop on a wattmeter. Ameritron sells a stand alone box, with several 1 kw pep rated /400W CCS LP filters in it]

##  check their wattmeters.. fat boy style  http://fatboyamp.com/...under "bird supplies"  They also seem to have developing the power figured out..and run em up to 20 vdc. ..using motor mauls and dahl xfmr's etc.

later... Jim  VE7RF
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EI9JU
Member

Posts: 61




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« Reply #43 on: September 22, 2012, 01:38:46 PM »

I was a bit late finding it topic but nevertheless it made very interesting reading.
Here's a bulletin issued earlier this year on the Martin Lynch site, one of the largest Amateur radio outlets in the UK:

"IMPORTANT NOTICE! Due to high failure rate of these amplifiers in the field ML&S have decided to discontinue the sale of the BLA-350. With a failure rate of almost 70% we were very concerned on reliability and therfore have withdrew them from sale. We do have a quantity of refurb units for sale in full working order at TRADE price. Please call the sales desk if you are interested."

Mmnnnn, this hardly fills one with confidence regarding RM build quality. Shocked
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MM0IMC
Member

Posts: 30




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« Reply #44 on: November 05, 2012, 12:09:47 PM »

I was a bit late finding it topic but nevertheless it made very interesting reading.
Here's a bulletin issued earlier this year on the Martin Lynch site, one of the largest Amateur radio outlets in the UK:

"IMPORTANT NOTICE! Due to high failure rate of these amplifiers in the field ML&S have decided to discontinue the sale of the BLA-350. With a failure rate of almost 70% we were very concerned on reliability and therfore have withdrew them from sale. We do have a quantity of refurb units for sale in full working order at TRADE price. Please call the sales desk if you are interested."

Mmnnnn, this hardly fills one with confidence regarding RM build quality. Shocked


Speaks volumes about RM's build quality! Shocked  I know of a couple of folk who use these amps to beef up their QRP rigs from home.  I wonder if their 1kW amp has build issues too? Huh
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