>
>> >It was not Rich's idea. Eimac recommends a shunt screen regulator
>> >for smaller tetrodes. I used the circuit in two amplifiers and
>> >dynamic screen V regulation was better than 1%. A caveat: Operate
>> >zeners at no more than 33% of rated dissipation.
>
>> If I remember correctly, the measurements made by GW4FRX (and/or
>> G3SEK?) showed a significant improvement in IMD if screen regulation
>> was improved from around 1% to around 0.1%. That's not the same as
>> saying that 1% regulation produces unacceptable results in the real
>> world, but shouldn't we aim for the better target? The effort of
>> building a better screen supply is usually minor compared with the
>> rest of PA building.
>
>Regulation will be much better than 1% if you wrap around the
>zeners with a gain stage. The overall cost will be the same, since
>you can use cheap HV NPN or PNP transistors and smaller zeners.
Smaller zeners have more dynamic R.
>In that case you can use a very high value resistor from the HV to
>the zeners,
true
>and the ESR of the zeners is less important.
>
blarney
- Rich..., 805.386.3734, www.vcnet.com/measures.
end
--
FAQ on WWW: http://www.contesting.com/FAQ/amps
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
|