...
>>Question: What would be the expected efficiency of this amp,
>>considering the tubes may be 15-20 years old?
>
>
>Efficiency is the same this year as in 1966 Ron. With good tubes expect
>60% or so.
well put
>> ........ Idling current is 135 ma which produces considerable
>>heat; a zener in the filament return line is my next project.
>>
For minimal distortion you need 75mA of ZSAC per anode. If heat is a
problem, why not use high speed VOX with high speed switching in the
amplifier? When one is not talking, zero dissipation occurs within a few
hundred milliseconds - which is pretty nice since it's more like talking
on the telephone instead of broadcasting at each other - a.k.a. 'lock to
talk'. . There's a high speed switching circuit in the 1/94 *QST*
article on amplifiers. If you use a modern radio, you need it to prevent
hotswitching.
>>Again, thanks to all for their posts. I compare this project to
>>rebuilding a sixties' big bore Mustang. It's big, ugly, but still fun!
>
Big is right. My old 20db gain 'tetrode with handles' amp. was 27.5
inches high - including the 8kV anode and 1.5kV screen supplies,
including the blower.
>More like a small block 351C . You need 4-1000A's to equate to a 429
>Cobra!
...... good tubes have handles.
Rich---
R. L. Measures, 805-386-3734, AG6K
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