[Amps] HV MOSFETs for RF

[Kevin Stover, AC0H]

All,

IMHO the problem with today's 100W radios is that they are designed for 
12V finals. Comparing a "modern" solid state radio designed to run on 
12V finals to a Collins 32S-3 is borderline ridiculous. There is a price 
to be paid for "no tune" and using 12V finals makes it worse.

If I was designing a final section for one of these rigs it would be a 
pair of 50V MRF-150's derated to 150W max out. They're plentyful, 
comparatively cheap, probably close to a matched pair of 6146B/W's for 
TS-520.
Of course there are going to be people who are unhappy not being able to 
run the rig "all knobs to the right", to the max of a pair of 
MRF-150's...300W, but too bad. Buy someone else's rig.

I'd bet a final section built and run like that would hit -40 IMD 
running full tilt boogey. Add a little pre-distortion and we'd hit -50dB.

The days of the 12V SSPA in rigs are numbered, or should be.

So... that leaves me with a rig that will do -45 to -50 IMD and an amp 
(AL-1500, Ameritron's number) that'll do -38. Hmmmm.

Let the anecdotes fly.



On 5/10/2017 11:17 AM, Manfred Mornhinweg wrote:
> Jim,
> 
>> ##  The 100w  K3  driver section is junk, both the driver and the
>> main 100 watt pa need a serious  re-design.
> 
> What exactly would you improve in that design?
> 
> I just had a look at those schematics. The driver section looks pretty 
> OK to me, while the 100W amp suffers from a typical design flaw that 
> also affects most other 100W radios from the last 20 years or so. But 
> it's really not easy to avoid that flaw!
> 
> I would be interested in seeing your suggestions for improvement, to see 
> whether or not they agree with my own.
> 
> Calling that design "junk" seems a bit over the top. It's no worse than 
> many others. In fact better than some...
> 
> Can you point me to some 100W broadband amplifier stage that you would 
> consider good? And some 10W driver that you would endorse, and why it's 
> better than the Elecraft "junk"?
> 
> Manfred
> 
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-- 
R. Kevin Stover    AC0H
FISTS #11993
SKCC #215
NAQCC #3441
ARRL