Greetings all, and happy post-Thanksgiving.
I'm progressing nicely on my first homebrew amplifier, a pair of 3-500z's in
GG. I have collected all the tank components (pi network) including a used two
section Radio Switch 86. It has enough positions for 160 to 10m.
My question is this: Most of the schematics that I've seen for a bandswitched
tank show the switch common connected to the low impedance side of the tank.
Is there a compelling reason for this?
I'm leaning towards connecting the common point of both switch sections on the
high side of the tank inductor. My reasons are as follows:
My tuning cap is an old E.F. Johnson, big, probably 7 kV spacing, and I've
measured 33 to 250 pF using a H-P impedance bridge.
To keep the tank Q reasonable on 10 and 15m, I'd like to switch some fixed C in
series with the tuning cap to lower the tuning range. I envision one section
of the bandswitch for this.
I need about 200 pF in parallel with the tuning C for 160m. Since my tank
inductor will be totally used on 160m (about 20 uH total), I envision having
one free tap on the second bandswitch to switch in the 200 pF fixed C in
parallel with the tune C.
I'd welcome any comments/suggestions/etc. on my plan. Replacing my tuning
capacitor with a vacuum variable is not an option.
Many thanks in advance,
Charlie N9CO
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