FM Subcarrier SCA Boards for Sale
 

I found Dave Jackway is still selling his excellent and inexpensive SCA
boards which tap off the FM detector. Here is a post I did way back in
'93 and the information is still good:

I recently ordered and received three SCA demodulator boards from SCS Radio
Technology after noticing an advertisement in Radio News. Bruce Elving's
SCA design uses a CA3089 IF/detector chip and a PLL (I designed his XR2211
PLL SCA demodulator) SCA. Bruce also sells FM receivers modified with the
boards.

What was interesting about the SCS SCA board design, while it uses a CA3089E
IF chip also, a multipole filter in front of the 3089 decreases main channel
crosstalk interference (by 60 dB). David's board is of excellent
construction, with no jumpers and small size to be inserted in an FM
receiver's FM detector stage (before deemphasis attenuates the SCA signals).
Anyway, three pretuned boards are available from SCS, 57Khz, 67Khz, and
92Khz - $30.00 each, $80 plus $7.00 P&H for all three.

I am satisified with the design and construction of each board. One area of
modification I would make is to monitor the SCA signal's multipath and level
with an x-y monitor. Use pin 13 of the 3089 chip for a signal level (scope
y) output and pin 7 for the y axis output. Of course levels must be set to
set vertical and horizontal traces. A flat vertical line, max amplitude, is
the ideal signal for tuning. A "wavy" line illustrates multipath. This is a
great tool for tuning FM signals...

SCS's Address and Phone Number:
SCS Radio Technology
5742 Fairoak Springfield, MO, 65810

Phone: 417-881-8401
(I have no affilication with SCS, only as a satisfied customer)