Date:02-06-93 00:24 From:Bill Cheek To:All Subject:PRO-43 S-Meter! Greetings Scanner Fans! It had to happen! The fundamentals for an S-Meter exist alive and well in the PRO-43! Only a simple circuit and your choice of meter, analog or LED, is required for a jim-dandy S-Meter function! The key point in the circuit is the cathode of D-302 located on the bottom (solder side) of the AF Board (middle board). You will need the Service Manual for the PRO-43 to find it as it's not marked and it would take me 10,000 words to guide you to exactly where it is located. Call Tandy National Parts at (800) 442-2425 to order your manual:approx $10. Now here is the deal: Locate D-302 and either build the following circuit right there on the back of the AF board in the vicinity of D-302, or solder a wire to the cathode of D-302 and route it to somewhere else more convenient to feed the below circuit. This wire ought not to be very long, though, say not more than a couple of inches. Refer to the ASCII schematic diagram as follows: PRO-43 PRO-43 D-302 existing T-302 x---o--|<-------x PRO-43 ckt / | Connect | here | 0.01-uF 1N34A |------||------o-------->|----o---o-----------> (+) | | | | \ | To the | 47-k / | S-Meter of | ohms \ = 0.01-uF Your Choice | / | (This should | 1N34A | | be a jack |-----|<-------o---o----------> (-) mounted on ^ PRO-43 Ground^ the case of Legend: the scanner. | 1. ---||--- and = are 0.01-uF capacitors; disk, mylar, monolythic, chip | 2. --->|--- and ---|<---- are germanium diodes, 1N34A | is cathode < is anode 3. o means a connection, preferably soldered 4. The 47-k resistor is self-explanatory, I hope. 5. -------- and | are wires/conductors. | | 6. x is existing PRO-43 circuitry If you use an analog meter, preferably a real S-Meter like salvaged from an old junked CB rig, then rig it as follows to connect to the circuit above: 5-k Trim Pot (+) --------/\/\/\/\---o--------| | | | This should |-------| | be a plug of + some sort to The S-Meter connect to the Terminals mating jack on - the scanner | | (-)-----------------------------| You can also build the 10-segment LED S-Meter as shown in Volume 2 of my SCANNER MODIFICATION HANDBOOK, available from leading mail order radio dealers everywhere. ISBN 0-939780-14-3 published by CRB Research Books, Inc. Commack, NY. After connected and working, locate the PRO-43 very near a known strong transmitter, perhaps a ham transmitter, a police cruiser, your favorite security guard's handheld or right next to a cordless telephone, or anything else known to transmit a strong signal. Tune the scanner to the frequency, and adjust the 5-k trim pot above so the meter reads exactly full scale. All other signals will read proportionally lower to yield "relative signal strength" measurements! A hell of a circuit here, boys & girls! Have fun! Developed & distributed by: Bill Cheek COMMtronics Engineering PO Box 262478 San Diego, CA 92196-2478 Ok to distribute, but credit appreciated. Thanks! Bill Cheek --- GEcho 1.00/beta+ * Origin:Hertzian Intercept, San Diego (6pm-1pm) 619-578-9247 (1:202/731.1)  Amsterdam View Our Stats   CLICK FOR A FREE DOMAIN NAMES HTTP://WWW.YOURNAME.TK FOR YOUR OWN WEBSITE IF YOU CLICK HERE AND YOU CAN VOTE FOR OUR FREE WEBSITES IN THE TOP 100 LIST  WANT A TOP RANKING ? USE THE ULTIMATE SOFTWARE SUITE FOR WEB SITE PROMOTION  FreeWebSubmissions Submit Your Site To The Web's Top 50 Search Engines For Free THE ALEXA BANNER, THIS BANNER GIVES THE DALLY STATISTICS OF THIS FREE WEB SITE The World of Free Packet Radio Software Amsterdam The World Of Free Packet Radio Software Amsterdam The Netherlands |