S-Meter for PRO-2004/5/6 & Other Scanners S-METER FOR THE PRO-2004/5/6, PRO-43, PRO-2035/2042 also the PRO-34/37/39 and PRO-2022 and possibly other scanners with the 108-136 MHz Aero Band ========================================================== This article/file is for the benefit of all. (c) 1995-96 Bill Cheek-COMMtronics Engineering This article/file is for personal use only and may NOT be placed on a CD-ROM nor any other media that conveys, stores, or transports for any monetary cost, without expressed permission of the author. This article/file can only be given away, absolutely free of charge. -Bill Cheek- Build the following simple circuit left of Points A and B on a piece of perfboard. The circuit to the right of A and B is optional, explained further below. |<-----Build on perfboard----->| |<--Project Box-->| in scanner o-------| Connect Jack Plug | | to Y .01-uF 1N34A A C v | Cathode>----||-----o--->|------o-----o----> (+) >--o-/\/\/\----o detector | | | 5-k | <+> diode --- --- \ Trimpot CB in 1N34A ^ --- / 68-k type scanner | .01-uF | \ OPTIONAL S-Meter | | | | <-> Ground >-----------o-----------o-----o----> (-) >--------------o Z B D |<---keep leads short--->||<----Any length leads ok---->| Diodes must be germanium, 1N34A or 1N60. Capacitors should be ceramic disks. Resistor and trimpot are not critical. The circuit to the left of Points A and B must be as shown. If you want to use an external CB-type S-meter, so much the better....just build the meter of choice into an attractive or functional project box with a cable of any length from the box to Points C and D which should be wired to a male RCA plug. Connect Point Y to the cathode of: PRO-2006: D-33 PRO-2005: D-33 PRO-2004: D-31 PRO-2022: D-29 PRO-2035: D-34 PRO-2045: D-34 PRO-43: D-302 PRO-39: D-202 PRO-34: D-117 PRO-37: D-122 Other Scanners: This mod may work with other scanners that have the civilian aero band of 108-136 MHz. If your scanner has 108-138 MHz and is not listed above, then find the last 455 kHz IF section, and locate the AM detector diode. Connect Point Y to the cathode of the AM detector diode. NOTE: This mod may not work with Uniden scanners. Keep this Point Y lead length very short, not more than an inch. Connect Point Z to scanner PCB or chassis ground and keep that lead short, not more than 1 inch. Points A and B are the metering points where any DC voltmeter can be used. Signal range will be about 0-1v. The circuit to the right of A and B is an optional CB type S-Meter, and should be used external to the scanner. Therefore, it is ideal to wire A and B (length not critical) to an RCA phono jack on the rear panel of the scanner for easy connection of the external meter. Otherwise, any DC voltmeter can be used directly at A and B including a bargraph LED display. If the external S-meter circuit is desired, then wire it as shown. Use a walkie talkie or other transmitter to send a strong signal into the scanner, and adjust the 5-k trimpot so that the meter reads exactly full scale. All other signals will then read proportionally lower. Most any analog CB-type S-Meter is ideal for this project, but the larger the face, the more readable it will be. There are thousands of junked CB rigs all over the planet, and most any CB or radio shop will have a bin full of them. The cost of a salvaged S-Meter should be negligible. You can embelish your S-Meter with a small pilot lamp behind it to illuminate the face. Many CB meters have such a lamp built into the body of the meter. You may have to tap 12-volt or other power from the scanner for the lamp, or provide external power. NOTE: I cannot and do not supply S-meters. I can and will provide technical support of this project on this forum or by e-mail. (c) 1996 Bill Cheek +----------------------------------------------------------------------+ | Bill Cheek E-mail: bcheek@cts.com FidoNet: 1:202/731 | | COMMtronics Engineering Compuserve: 74107,1176 | | World Scanner Report Voice Phone: (619) 578-9247 1:30pm-5:30pm | | PO Box 262478 BBS & FAX: after 5:30pm & before 1:30pm | | San Diego, CA 92196-2478 24-hrs, weekends/holidays | | WWW home page: http://ourworld.compuserve.com/homepages/bcheek | | FTP Sites: ftp://ftp.cts.com/pub/bcheek | | ftp://ftp.cts.com/users/crash/b/bcheek | +----------------------------------------------------------------------+