"DougSlug" wrote in message
...
You're correct that the audo tapes would only have audio information, but
the SCA information is also in the baseband signal except that it's
outside the audio bandwidth that the tape recorder would have recorded due
to AF filtering in an ordinary FM receiver. As I understand it, the SCA
information is filtered from the demodulated signal before it is sent
through the AF filter normally used for the audio output of the "main"
(primary carrier) baseband signal.

It is filtered out by the Stereo demultiplexer before it gets to any audio
stage. To receive SCA, you will need to tap into the receiver after the
product detector (discriminator, pll, whatever) and before it goes to the
demux.

An SCA receiver is effectivily a 67khz receiver plugged into your 100MHz
receiver.

There is a LOT of info out there from people doing the same mod for the
purpose of receiving data/pager transmissions. Search under " discriminator
tap" and see what comes up.


Nana