Date: Sat, 13 Feb 2021 14:03:03 -0500
From: "Joe Subich, W4TV" <lists@subich.com>
To: amps@contesting.com
Subject: Re: [Amps] Clipperton L - GI-7B
<All of this is a result of using output devices rated for saturated
<power output at 12 Volts. If one looks at the spec sheets for all
<of the devices used in the mentioned transceivers, *IF* the spec
<sheet shows parameters for IMD, it will be significantly better at
<60 to 80 W PEP than at 100 W PEP.
<Amateur transceiver manufacturers *MUST* get their design heads out
<of where the sun don't shine and start using 24V devices for 100W
<power levels and 48V devices for 200W power levels. Driving solid
<state amplifiers well past the 1 dB compression point guarantees
<IMD3 worse than -30 dB and it is time to stop accepting such garbage.
<73,
< ... Joe, W4TV
## Funny thing is, the Icom marine 100 watt xcvrs are 10 db better for
IMD, vs the Icom ham junk specs.....
and both operate on 12 vdc. The marine versions use a lot more NFB.
## On another note, while LDMOS might be all the rage for 1.5 kw SS
amplifiers, VDMOS devices offer more simplicity.
They, microseimi now have VDMOS devices up to 700 vdc. This simplifies a
lot of things. Like an output Z of 50 ohms for 150 watts pep out...when
run at 125 vdc.
## A buddy in CT designed and built a 2-3 kw pep output VDMOS amp, that
will operate on either 120 vac..or 240 vac. Run on 120 vac,
it uses 2 x separate power supplies, with inputs in parallel..and isolated
outputs. On 240 vac, same 2 x power supplies used, again, with isolated
outputs.
Kicker is, NO xfmr used. And yes, the entire chassis is bonded to the
green ground wire. It senses the drive level, and freq, and if drive is too
high, the relays
wont even activate. If drive is a normal level, then increased, it will
kick offline. If it overheats, it kicks offline. It’s got 8 levels of
protection built into it,
you just cant blow it up, or damage it. So far. so good. Bunch of testing
being done on it this week. Stay tuned.
Jim VE7RF
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