"Qas" wrote in message
om...
Hi,
I am new to ham radio. Well I found lots of QRP receiver circuit on
web, I tried to build some. Everything going to be OK, except making
coil inductors. I don't know how to calculate them, with type I need
(air core or slug tuned), what a difference between coil and RF choke.
Let's assume I need a 100uH coil. How to star making it. I looked for
factory made coil at my radio shack store, but I only found bobbin for
coil.

If you know any interesting link on this topic, please let me know.
I'll appreciate any comment or help.

100 uH is quite a lot of inductance for a radio circuit, expecially at HF.
Inductors around 10 uH or less are very easy to make using toroidal cores.
For instance, a 5 uH inductor is about 32 turns on a T50-2 core. I use a
simple Excel spreadsheet for this sort of thing.

RF chokes are basically inductors, but specifically intended for stopping RF
from going somewhere unwanted. They are usually wound on ferrite cores, and
tend to have fairly high inductance values. They are used on their own,
usually, unlike coils, which tend to be used with capacitors. RF chokes have
a self-resonant frequency due to their self-capcitance - this needs to be
checked when using them and the self-resonant frequency avoided.

73, Leon
--
Leon Heller, G1HSM

http://www.geocities.com/leon_heller