Back when I was in college I majored in electronic communication which also included AM radio stations. So I have been reviewing what I used to know about AM radios starting with crystal receivers. Most of the tuning caps of that era were 10pf to 365 pf. The popular antenna of that era for handheld receivers what is a ferrite coil antenna. I'm trying to recover what the inductance range these antennas were in. The frequency range the tuner had to cover was 530 Khz to 1600 Khz. For the life of me I can't remember what the antennas were in inductance. Discuss?

 

Use this formula:

ω^2 = 1/(LC)

ω = 1 / √(LC)

where ω = 2πf

85 μH and 300 pF results in a resonant frequency of 1 MHz.

Or you can find an LC resonant frequency calculator online.

 

Did that:
https://www.omnicalculator.com/physics/resonant-frequency-lc
C=10pf L = 250µH fo = 3.1831MHz
C=365pf L = 250µH fo =533.49KHz
I was trying to figure out the inductance of a ferrite antenna, just recreating an exercise I did in my 20's. I believe it was 250µH which seems to work.

I could do much better this time around 40+ years later (oops, did I say that out loud?). I didn't know about schottky diodes back then. It is a bit dismaying I can't do math like I used to.

 

Yes, that checks out. I get 247uH.

At the low end, 40pF is required. But stray capacitance will likely be a good portion of that, hence the low of 10pF.

 

This is my SW DX aerial this morning.

 

When I was a kid I would buy 100' of wire and attach it to a tree with a screen door spring to keep it tight. Got fantastic shortwave reception But the wire kept breaking. Finally I gave up and stuck with an indoor shorter wire.