Hi Tim,
I normally do that mod to SB-220's and other amps.
> So what benefit did directly grounding the grids bring?
If you put a lug by each grid pin, you can actually remove turns
from the suppressor without running into instability compared to a
similar test with the grids grounded through the caps.
I don't remove turns from the suppressors in operating PA's since
the 220 suppressor is fine as is, but only use this as an A-B test
indicator of how stability changed.
> More output on any or all bands for the same drive power?
Well, if you mod the PA for 160 M it works a lot better there. If not,
you only see a slight gain flatness improvement. Also, you see
less input SWR change as the tuning control is adjusted. That's a
good sign also.
> The same output on any or all bands for LESS drive power?
Not a great amount, but there is a slight improvement in gain.
> A better VSWR between the radio and the amplifier input? The stock 220
> input VSWR on 10 and 15 is pretty poor.
I've always has to redo the input, so I can't say which way it goes
without the changes. I do know the input SWR varies less as the
plate control is rotated around the plate current "dip" and maximum
output is closer to dip center.
> Does the amp tune smother on 10 and 15?
As above.
73, Tom W8JI
w8ji@contesting.com
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