Thanks for info. Of course you need always a high frequency screen grid cap
or grounded g2. But you did not get my point: if your g2 voltage is slowly
following your SSB-signal you do not get envelope distorsion but a slow gain
variation. Of course your parameters are changing as well and you may very
well get more distorsion from this. Anyway, this very compact NAG 144 MHz
linear had almost the same output with 3 or 10 watts drive and the only
explanation I can give is as above.
HEJ DAA DE HANS/SM5KI
----------
>Från: measures <measures@vcnet.com>
>Till: "sm5ki" <sm5ki@algonet.se>, "Ian White, G3SEK"
<G3SEK@ifwtech.demon.co.uk>, "AMPS" <amps@contesting.com>
>Ämne: Re: SV: [AMPS] Tetrode Amp Help
>Datum: tor 9 dec 1999 14.34
>
>
>>
>>Hej!
>>
>>Do you really need a stabilized screen grid supply?
>
>? On page four of Eimac's specification it says that the screen voltage
>must be maintained constant.
>
>>If the g2 voltage
>>follows relatively slowly the envelope of a SSB signal, you should get a
>>only a slow gain variation in the tube???
>
>? Not slow. Anode current increases exponentially with increasing
>screen potential.
>
>> You have then to use a large
>>condenser across the g2 voltage.
>
>? Why? One is trying to bypass HF and VHF energy in the anode-grid
>feedback path. .
>
>>If I remember right ( and I may be wrong
>>)looking into the NAG gg two meter 4CX350 linear the g2 voltage adjusted
>>itself
>
>? Eimac recommends constant screen voltage for all tetrodes and all
>pentodes in linear service. .
>
>>to the average drive level and you could use anything from 3-10 watts
>>of drive with good linearity.
>
>? Only if screen potential is held constant.
>
>cheers, Hans.
>
>- Rich..., 805.386.3734, www.vcnet.com/measures.
>
>
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