[Amps] Clipperton L - GI-7B

Chris Wilson chris at chriswilson.tv
Wed Mar 3 09:47:17 EST 2021

Hello Jim,

 Tuesday, February 23, 2021

 Have any schematics and / or build details been published for home build HF band VDMOS amps? This sounds the way forward, better matching to the ubiquitous 50 Ohm antennas, no insane currents, blah blah. I am assuming this may be the VDMOS amp you are talking about Jim?


Any info on practical HF VDMOS amps welcome!

Best regards,
 Chris          mailto:chris at chriswilson.tv

JT> Date: Sat, 13 Feb 2021 14:03:03 -0500
JT> From: "Joe Subich, W4TV" <lists at subich.com>
JT> To: amps at contesting.com
JT> Subject: Re: [Amps] Clipperton L - GI-7B

JT> <All of this is a result of using output devices rated for saturated
JT> <power output at 12 Volts.  If one looks at the spec sheets for all
JT> <of the devices used in the mentioned transceivers, *IF* the spec
JT> <sheet shows parameters for IMD, it will be significantly better at
JT> <60 to 80 W PEP than at 100 W PEP.

JT> <Amateur transceiver manufacturers *MUST* get their design heads out
JT> <of where the sun don't shine and start using 24V devices for 100W
JT> <power levels and 48V devices for 200W power levels.  Driving solid
JT> <state amplifiers well past the 1 dB compression point guarantees
JT> <IMD3 worse than -30 dB and it is time to stop accepting such garbage.

JT> <73,

JT>   <  ... Joe, W4TV

JT> ##  Funny thing is, the  Icom marine  100  watt xcvrs  are 10 db
JT> better  for  IMD, vs the  Icom  ham  junk  specs.....
JT> and both  operate on 12 vdc.   The marine versions  use a lot more  NFB.

JT> ##  On another note,  while LDMOS  might be all the rage for  1.5
JT> kw  SS amplifiers,  VDMOS  devices  offer  more simplicity.
JT> They,  microseimi  now have  VDMOS  devices up to 700 vdc.   This
JT> simplifies a lot of things.   Like an output  Z of  50 ohms for 
JT> 150 watts pep out...when  run at  125 vdc. 

JT> ##  A  buddy in  CT  designed and  built a  2-3 kw  pep output 
JT> VDMOS amp, that will operate on either  120 vac..or  240 vac.   Run on  120 vac,
JT> it uses  2 x  separate power supplies, with inputs in
JT> parallel..and isolated  outputs.  On  240 vac,  same  2 x power
JT> supplies  used, again, with isolated outputs.
JT> Kicker is,  NO  xfmr used.  And yes, the  entire chassis  is
JT> bonded to the  green ground wire.   It senses the drive level, and
JT> freq,  and if  drive is too high,  the relays
JT> wont even activate.   If drive is a normal level, then 
JT> increased, it will  kick offline.   If it overheats, it  kicks
JT> offline.  It’s  got  8  levels of protection built into it,
JT> you just cant  blow it up, or damage it.   So far. so good.  
JT> Bunch of testing being done on it this week.  Stay tuned.

JT> Jim   VE7RF
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