David G4FTC wrote:
> Searching the amps archives, I know this question has been asked before
> but........
>
> Apart from squeezing/expanding the coils of the input T network to obtain a
> satsifactory match, has anyone tried using a PI-L or similar network to
> simply the input tuning?
>
> The original W6PO design made one of the L in the T network variable to
> simplifiy obtaining a match - but the chances of getting a suitable
> ajustable core are probably nil, so adding a second variable C into the
> network would seem to be a logical move.
>
> Before I take an electric drill to the chassis to mount another C, does any
> one have any thoughts why this may not work?
>
> What worries me a little is that most tube VHF amplifiers use the same basic
> T network for the input, and no-one seems to have considered that the T
> needs to be improved.
Maybe, but make two coils like the airspaced one, spend just a few
minutes getting them squashed/stretched right and you don't need to
touch it again for 20 years. Beats drilling holes anytime :-)
Steve
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