Date: Wed, 10 May 2017 19:01:40 -0500
From: "Kevin Stover, AC0H" <kstover@ac0h.net>
To: amps@contesting.com
Subject: Re: [Amps] HV MOSFETs for RF
<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.
### marine SSB gear runs just fine on 11-12 vdc..and meets ITU IMD specs,
go figure. Before that, marine ssb gear would meet the even more stringent
FCC specs.
## A DC to DC converter would perhaps solve a loot of issues, and still
allow for 12 vdc operation. The car audio folks have already figured that one
out.
## The 2 x VRF-151 SS amp in the arrl hand book has good imd, when run
at 200-250 w out..and superb at 100-150w. A local buddy built it.
## 300W with 2 x MRF-150s is pushing your luck. If you wanted
300w out, use 4 x MRF-150s.
## use the pre-distortion, and take the sample from the output of your
AL-1500, and its -38 will improve to –48 to –52...problem solved.
Jim VE7RF
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