[Amps] Question for the tetrode experts

Peter Voelpel dj7ww at t-online.de
Fri Nov 8 16:30:44 EST 2013

What is the loaded Q of your Pi circuit?
Is that sharp tuning with the load capacitor on all bands?

When tuning the anode capacitor, peak screen current with it and use load
for the correct screen current of about 35mA with a good tube.
That should coincidence with about 1500-1600W out.


-----Original Message-----
From: Amps [mailto:amps-bounces at contesting.com] On Behalf Of Vic K2VCO
Sent: Freitag, 8. November 2013 22:09
Cc: amps at contesting.com
Subject: Re: [Amps] Question for the tetrode experts

I have a vernier on it. Maybe I exaggerated -- it's not all that bad, just
different. It 
is smooth. I just need to get used to it. A plus: the screen meter is very
useful as a 
tuning indicator!

On 11/8/2013 1:01 PM, N1BUG wrote:
>> Tuning is VERY touchy. You really have to have the loading right or the
screen current is
>> excessive in either direction.
> None of my 4CX1000A or 4CX1500B amps were all that touchy, from 1.8 to 144
MHz. Screen
> current does vary with loading, from negative through zero to positive,
but it is a smooth
> and easily controlled change provided the loading capacitor has some
reasonable rate of
> adjustment. I prefer vacuum variables, but if using an air variable I put
a vernier drive
> on it.
> With vacuum variable tune and load caps in a pi network, I have no problem
going from band
> to band by using logged presets. Of course the presets have to be changed
if I make any
> change to the antenna system, and tuning needs to be verified if there is
any possibility
> of weather conditions affecting the antenna (ice or snow).
> 73,
> Paul N1BUG

Vic, K2VCO
Fresno CA
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