[Amps] Non-linear linear

[Jim Thomson]

Date: Fri, 31 Jan 2014 11:51:36 -0800
From: Paul Baldock <paul at paulbaldock.com>
To: "amps at contesting.com" <amps at contesting.com>
Subject: Re: [Amps] Non-linear linear


Well ignore everything I said. It's a measurement error. I was 
assuming the input SWR was relatively constant with power levels and 
basing my input power variation on a voltage measurement on the scope 
sampling the input coax to the amp. Turns out the input SWR varies a 
lot with power input on all bands, for example on 20M 1.4 at 75W, 1.1 
at 35W, and 1.4 at 10W drive.

So now the new question, is such an input SWR variation typical of a 
GS35B?  My 2 x 3-500Z amp is almost constant with input drive (as is 
Jim's VE7RF)

- Paul

##  On my array solutions power master watt meters, they have an option on there
called ... net power.    Net power is simply  forward power minus reverse power.  
This is the mode I normally use.  This would be no different than doing the same thing
with any bird wattmeter.   What I have noticed on a lot of GG amps is... the lower the
input swr, the higher the grid current, and the higher the plate current and also power output.
Also, depending on which brand and calibration of the SS Xcvr, with higher input swrs, 
the lower the power output of the xcvr.   My yaesu  FT-1000D  will easily do 100 w out
into a 3:1  swr.     My  yaesu  FT-1000-MK-V  is under 100 w   into a 2:1  swr.   A lot of xcvrs will
drop off  with a 1.7:1  swr. 

##  still, it does not explain why ur input swr on 20M is lowest at  35w of drive.   Have u tried
tweaking the input swr when operating normal 75-100w  drive levels ?? 

##  I checked my drake amps..and input swr  doesn’t change at all  between 5 watts  of drive
and 110  watts of drive.   B4 you go off a tangent, you might want to try a known good spare tube.
Then compare the results.   You may well get the same swr anomaly but  it could be quire different again.
If swr is still haywire, then proceed with other possible fixs. 

##  I have yet to ever see a setup whereby the tuned input and PI  kw  output  share the same bandswitch..yet use
different wafers.   Two separate switchs, one below the chassis and one above the chassis..and driven by a plastic chain
is nomal..or a relay scheme etc.  

Jim  VE7RF