> -----Original Message-----
> From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com]
> On Behalf Of Jim Thomson
> ## he also erroneously states that a PI network wont' suppress
> harmonics..
> which is nonsense. The PI tuned input, inside a GG amp, will attenuate
> harmonics. In the ten tec manual for the Centurion 2 x 3-500z amp...
> they refer to the individual pi nets.. as ' LP filters' which is
> actually
> what they are... and is correct.
>
> ## the idea behind the Pi-net is to kill the harmonics of the amp
> itself,
> not the exciter driving it. The Pi net will provide the required
> flywheel
> effect with loaded Q of aprx 3. It also does any Z matching. It works
> best,
> then the C2 cap [facing the cathode].. is closest to the cathode. If
> the tube's
> input Z is aprx 50 ohms... 50 ohm coax can be run between output of
> tuned input
> and the cathode, with no ill effects.... it's like a line extension.
> If the tube is
> 25/35 ohms... then parallel 50/70 ohm coax can be used.
>
> later... Jim VE7RF
The pi network won't kill harmonics generated in the amp but the output
capacitor of that pi network (on the cathode side) will reduce the harmonics
generated in the amp.
I don't think that you have to worry about the impedance of any coax used
inside of the amp as it does not really look like a transmission line with
those short lengths. I believe that it can be treated as just adding
capacitance.
73
Gary K4FMX
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