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From: parnass@ihu1h.UUCP (Bob Parnass, AJ9S)
Newsgroups: net.ham-radio
Subject: Re: Update: eavesdropping on SCA transmissions
Message-ID: <499@ihu1h.UUCP>
Date: Wed, 6-Mar-85 20:01:37 EST
Article-I.D.: ihu1h.499
Posted: Wed Mar  6 20:01:37 1985
Date-Received: Fri, 8-Mar-85 03:14:24 EST
References: <8666@brl-tgr.ARPA>
Organization: AT&T Bell Laboratories
Lines: 27

> SOUNDS LIKE A LOT OF TROUBLE JUST TO LISTEN TO SCA. I HAVE BEEN
> LISTENING TO SCA FOR AROUND 8 YRS NOW. LOOK AT ONE OF THE OLDER
> SIGNETICS APPLICATIONS BOOKS AND THERE IS A SLICK LITTLE CIRCUIT THAT
> WILL ALLOW YOU TO DO IT WITH A 565 PHASE LOCK LOOP CHIP. THE 565 DOES
> THE DETECTION AT 67 KHZ WHICH MEANS THAT YOU DON'T NEED TWO RECEIVERS!!.
> JUST TUNE THE FM RECEIVER AND THE PLL DOES ITS THING!!
> 
>                           REGARDS,
> 
>                           VAL L. ERWIN
>                           W5PUT

Thanks for the advice, Val. I built the Signetics 565 circuit in my lab,
but alas, it doesn't work!

The detector output of the average AM/FM radio is not high enough
to drive the 565. An additional stage of amplification is needed. 

I spoke with the proprietor of FM Atlas, who had the same results
with the 565 circuit.

Please post details of the simple circuit you've been using to detect SCA 
for 8 years. I might experiment with the XR2211 next, but it's a $6
chip. The 565 was on sale at Radio Shack for $1.19.
-- 
===============================================================================
Bob Parnass,  Bell Telephone Laboratories - ihnp4!ihu1h!parnass - (312)979-5414