[Amps] Clipperton L - GI-7B

Jim Thomson jim.thom at telus.net
Tue Feb 23 12:10:35 EST 2021

Date: Sat, 13 Feb 2021 14:03:03 -0500
From: "Joe Subich, W4TV" <lists at subich.com>
To: amps at 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.


  <  ... 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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