[AMRadio] RE:Fun with coils and caps!

[Brett Gazdzinski]

Hello all AM,ers!
I have been doing lots of experiments with circuits
for the L.O. for the home brew receiver, and learning a lot.

I tried a hartley, and did not have luck with that, and don't
want taps on the coils, I tried a colpitts and had very good results.

I tried air wound coils and had good results, and I tried
coils wound on slug tuned forms, and had luck with them.
I put a slug tuned coil in a can (was a 8 pin to 9 pin
tube converter type thing) with the slug out the top,
and had very good results with that.
I played around with values of vari caps, trimmers, and the
circuit caps, and adjusted the tuning range down to where
it will work well...170 KHz on 80, 250 KHz on 40 meters.
(some work still to do here).

It seems somewhat stable, even though the tuning cap
has clip leads connecting it....
It seems stable listening to it in the r390 with the BFO on.

The slug tuned forms are nice, as you can adjust them
without unwinding expensive B+W coil stock.

After some more playing with the tuning range, I will start
on the rf amp and mixer stages.

The IF stages should be somewhat easy, but there is the AGC,
s meter, bfo, xtal calibrator, etc...

The only things I bought so far is some ceramic coil
forms and tube base type plug ins from AES...nice
but fragile ceramic forms, a bit small for 80 meters...

Playing with this stuff is fun, sort of like a puzzle,
a little more capacitance, a little less coil, etc, to
get the frequency range I want...

Brett
N2DTS