Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/18/84 exptools; site ihu1h.UUCP Path: utzoo!watmath!clyde!burl!ulysses!mhuxr!ihnp4!ihu1h!parnass 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