Larry,
> Using your numbers and assuming the SWR issues are excess inductance,
> the inductance necessary to turn 50 ohms to a 1.5:1 SWR on 2m is ~23nH.
> If you were to put 8pF from the center pin to ground at the connector of
> the dummy load your 2m SWR would drop to 1.17:1 and the HF SWRs would
> get either slightly better or be virtually unchanged.
I didn't even measure whether the raised SWR on VHF is due to series
inductance, parallel capacitance, or whatever. When I made that PI
circuit, I was in a hurry to test a 1kW rig I had repaired for a
customer. So I hacked together a quick PI with two air-insulated trimmer
caps, which would allow me to tune the thing to 1:1 pretty much
regardless of what the problem was!
Nowadays I'm the proud owner of a fancy MFJ-259B (isn't it fancy...?),
so I could actually measure what the problem is, and apply the exact
cure. Someday I will do, I promise!
Manfred
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