Calculating the 80M LC Circuit

I was able to find an online calculator that will give me the circuit components for an 80M LC tank circuit:

I happen to know that my Palstar roller inductor goes up to at least 20 uh, and while my giant Palstar variable capacitor goes up to 450 pf at 4.5 kv, I’d like to try to use a smaller E.F Johnson variable capacitor that is also high voltage but has a smaller footprint. Its capacity is 20 – 251 pf.

When I plug in values near the middle of each component, I get resonance between the 75 and 80M band. This means I should be able to get a much better match at the antenna and then I will be able to take the AT2K out of the circuit as 160, 80 and 30 will all be within range of the SPE amplifiers ATU range. I will probably keep the AT2K in line – in case I have to use the Inverted L on another band that will require a tuner, but keep it switched direct bypassing the actual tuner.

So – this relay switching network has proven to be an invaluable tool and “platform” for testing and playing with antennas and getting the match just right. There is nothing as good as simply making the antenna resonant, and while that is easy to do on a mono-band antenna, its really tricky when you try to multi-band an antenna (at least beyond two “sympathetic” bands like 160 and 30M).

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