Xref: utzoo sci.electronics:19490 rec.radio.amateur.misc:1901 Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!mips!pacbell.com!ucsd!nosc!crash!hale!system From: system@hale.UUCP (System Administration) Newsgroups: sci.electronics,rec.radio.amateur.misc Subject: Re: FM SCA Subcarrier Demodulation Message-ID: Date: 21 Apr 91 09:07:19 GMT References: <1991Apr19.050618.23977@elroy.jpl.nasa.gov> Organization: Hale Telecommunications San Diego CA Lines: 40 szeto@kilroy.jpl.nasa.gov (James T. Szeto) writes: > After reading the FCC Rules and Regulations concerning the engineering standa > for subsidiary communications (SCA), I was wondering if someone would give a > clearer understanding on how SCA is added to the FM signal and how it is > recovered from the signal. Also, I'm looking for a reference where I may fin > an example circuit which recovers SCA. > SCA is used to transmit various programming, usally on a subscription basis, services like background music are the most common, but there have been some dabling with data transmission, paging services, etc... The FM signal (without getting into tech) generates two sidebands, which can be modulated to carry additional information, the decoder just adds an offset to the recieved signal to recieve the SCA (also known as MPX for Multiplex.) North Country Radio (PO Box 53, Wykagyl Station, New Rochelle, NY 10804) sells a kit for SCA/MPX decoding for $75 and $2.50 S&H, I believe the company just sells kits that Rudolf Graf and William Sheets come up with, which appear in electronic mags as "Build This" type things. Panaxis Productions (PO Box 130, Paradise, CA 95967-0130) sells one also, and has a much larger catalog, Ernie Wilson even has a kit for SCA Generation if you want to that involved, my catalog is not handy for prices, sorry. ($140 I think for the SCA Generator) This is very basic, note the time if you want to flame for gross lack of technical detail. Future BE in slavery. --------------------------------------=--------------------------------------- System Administrator Hale Telecommunications Public Access system@hale.uucp 619-660-6734 8N1 24 Hours --------------------------------------=--------------------------------------- ------=---------------------------------------