## 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.
SB200, SB220, L7, etc.
73,
... Joe, W4TV
On 2/1/2014 9:21 AM, Jim Thomson wrote:
Date: Fri, 31 Jan 2014 11:51:36 -0800
From: Paul Baldock <paul@paulbaldock.com>
To: "amps@contesting.com" <amps@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
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