[Amps] Non-linear linear

[Joe Subich, W4TV]

> ## 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 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
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