[Amps] Dummy Load Blues

[Manfred Mornhinweg]

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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