[AMPS] Resonances

[Steve Thompson]

In message <19980514.201648.9535.4.km1h@juno.com>, km1h@juno.com writes
>
>
>Steve, next time run the test with the cap in-circuit. Several years ago
>I ran the SB-230 on the analyzer and found multiple high impedences
>100-300MHz. 

I'd love to, but the amp has been put on 6m and I don't have any othe hf
PAs - I'm not allowed as I can't send morse on a straight key.

>If you look at Heath construction you will find the Tune cap has brass
>end plates, which sit on cad plated steel washers which then are in
>contact with the aluminum chassis. All held together with a pair of 6-32
>screws and no shaft to panel contact. Talk about inviting problems.
>Then you throw in a  "VHF" choke in series with the plate choke that is
>inches away and in parallel with the 80-20M tank coil AND has a series
>resonance around the reported parasitic frequency and you wonder why
>almost a dirty look will cause a zap.

I've long thought exactly the same.


Cheers, Steve

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