Following some success with a W3EDP I am playing with End Fed Half Wave antennas, at the moment for 80m. I have on the bench a link coupled parallel tuned circuit, and its doing a lovely job of transforming a resistive load of between about 3k ohms and 5k ohms into a 50R resistive load. Its almost like magic to an electronic simpleton such as myself.
This is all fine, and I have a reasonable understanding of how an EFHWA works according to AA5TB at his excellent page on these matters:
The thing is, how do I calculate the impedance at the end of a 1/2 wave bit of wire cut for 80m? What will actually happen is I’ll go out now with some wire and see what happens. But I’d like to be able to do the whole thing “by the book” - I’ve figured out the values of my capacitor and inductor, calculated the amount of turns on the toroid etc etc, but it would be better if I knew how to calculate the impedance of the end of a bit of wire!
Can anyone help?
PS. I have tried modelling such a thing in MMANA, but the output just isn’'t making much sense to me!