Re: 80 meter bpf toroid winding 30 turns givel 4.3 micro Henrys, not 3.8

Bob Benedict, KD8CGH

I second Kees advise on tuning by turn spacing.

I have also had to remove turns from LPF torroids. I put a small modeling study in the files section
that you can use to compare your sweep to.

One issue with a VNA is calibration. You should calibrate at the point of device test. I built a LPF test holder along with plug in calibration devices for open, short, 50 ohm load and through. Here is a post on it
and a nice commercial version here

Finally here are two posts I found helpful from Allison


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