ORIGINAL MESSAGE:
On Sun, 21 Feb 2010 16:42:36 -0500, "Gary Schafer"
<garyschafer@comcast.net> wrote:
>Leave the CLC (pi network) input circuit in there. A broadband input will
>not provide the flywheel effect that you need. Neither will an LCL do the
>job as there needs to be capacitance from cathode to ground that you only
>get with the CLC type or a parallel tuned input circuit.
REPLY:
I agree and would take it a step further. The higher the Q of the
input circuit, the less tendency toward VHF parasitics. Why? A very
low Q input circuit will be very braodbanded and may allow the tube to
have enough gain at VHF to oscillate. The higher the Q at HF, the
lower the VHF gain.
I built my 8877 amp with a simple parallel resonant input circuit with
a Q of five on all bands from 160-10 meters and it is perfectly stable
without a VHF parasitic suppressor at all. Any time you can eliminate
the VHF parasitic suppressor, you should, IMO. They are nothing but
trouble.
73, Bill W6WRT
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