BFO for 465kHz +/- 10kHz
 

"Pete KE9OA" wrote in message
...
http://home.att.net/~n.gianakopoulos...ome.html-.html

The above URL should help quite a bit.............I have a universal
product
detector up there, that will work anywhere from 410 to 600kHz, if you use
a
black core Toko I.F. transformer that has an inductance in the 600uH
range.
Just make sure that you have the transformer oriented so the the primary
tap
is about 25 to 35% above ground. Some transformers are wired so that the
tap is reversed.

Pete


Radio Shack might have a suitable coil in thier inductor assortment. I
found a few in those packs, and I used one to make a transistor Hartley
oscillator for doing alignments. I don't know if all the inductor
assortments have the 455 kHz transformer, or if Radio Shack still sells the
assortment. The transformer has 5 pins, the side with 3 pins has the pins
you'd use.

I don't know what transistor I used or what current I biased it. I don't
think any of that is critical. It worked fine on my first try. I got the
circuit out of an ARRL handbook. There's plenty on Hartley oscillators on
the web.

Frank Dresser

Series-tuned Colpitts (Clapp) oscillator.

Coil: 250 turns 3/4" long on a 1/2" diameter form, scramble wound. Should
give roughly 600uH of inductance.

Cap: 100pF varable parallel with enough capacitance (determined
experimentally) to give you an Fc of 465 KHz with the variable cap at 50%.

--
Gregg
*It's probably useful, even if it can't be SPICE'd*

You might realign the radio's IF to whatever it takes (465 - 2.7= 462.3 kHz?)
to get 40M LSB.

(I think I put the oscillator on the correct side for LSB.)

Bill