.....
>Does any one know the reason why Heath would chose to float the grids
>above
>ground on the 500z tubes. they are bypassed for rf thru a couple of chokes
>and capacitors, it seems to me it would make more sence to ground them
>directley to the chassis, for better isolation and stability.
I have tried direct-grounding the grids and grounding the grids through
3, 200pF capacitors. The grid's self resonant frequency is not
significantly different either way. Amplifiers that use
directly-grounded grids seem to oscillate occasionally at VHF, as do
amplifiers that use the C-bypassed grid approach. If you want to improve
VHF stability, you might try decreasing the VHF-Rp of the parasitic
suppressors.
cheers, Dick
Rich---
R. L. Measures, 805-386-3734, AG6K
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