Andrew Holme wrote:
"Anthony Fremont" wrote in message
...
Hello all,

I was playing around and saw that my junk box had all the parts so I
started tossing this together:
http://newenglandqrp.org/files/w1aw-receiver.jpg
The problem is (well I think it's a problem) is that I'm all the way
down to a 10pF cap for the crystal trimmer and the highest frequency
I can get out of it is still less than 3580kHz. Pleae correct me if
I'm wrong, but I'm thinking that the 20uH inductor is supposed to
pull the colorburst crystal high in frequency then the adjustable
cap should be able to tweak it back down. Higher capicitance does
result in even lower frequency. I made the 20uH inductor by
wrapping 17 turns on an old amidon FT50-61 ferrite toroid. I don't
have any way to measure the inductance, but by my calculations it
should be approximately 20uH.

You have a capacitor and inductor in series.
Capacitive reactance = -j/(wC)
Inductive reactance = +jwL
The net reactance [jwL-j/(wC)] may be capacitive (negative) or
inductive (positive).

I understand that, but I don't use values like j and w, just 2, f and PI.
;-)

Reducing the inductor makes it less inductive i.e. more capacitive.
Reducing the capacitor also makes the net reactance more capacitive.

You turned your trimmer all the way down to 10pF and it wasn't
enough, so try taking a few turns off the inductor.

I took it out, and it's still too low in frequency. :-( Back to the
drawing board I guess.