Newsgroups: alt.radio.scanner From: riyadth@boi.hp.com (Riyadth Al-Kazily) Subject: A (useless?) modification for the PRO-38 Sender: news@mail.boi.hp.com (News Server Project) Message-ID: Date: Fri, 4 Dec 1992 23:18:42 GMT Organization: Hewlett-Packard Company / Boise, Idaho Lines: 95 Modifications for the Radio Shack PRO-38 10ch scanner These PRO-38 modifications may also apply to the current PRO-41, and the Uniden BC50XLT and BC55XLT scanners, which appear to be the same unit in different packaging. Initially I wanted to enable my scanner to receive TV audio bands, just for fun. This started a quest for modification information, and I learned a lot about what can and can't be done with a scanner. Unfortunately, I didn't learn until after I performed this modification that TV audio (and FM radio) is broadcast in WFM (wideband FM), but most scanners only receive NFM (narrow-band FM). This results in major garbling of the sound when the scanner is tuned to a TV audio frequency. Anyway, on with the modification. I purchased the Realistic Service Manual for the PRO-38, part number 20-139, for a paltry $5.28 and a 1 week order delay. In it I found quite a bit of useful information. It contains full board layouts, a block diagram, a detailed schematic, and some pinout information for the UNIDEN UC-1143 microprocessor which controls frequency selection. This is in addition to the test and alignment procedures. There is even a nifty reset/test mode [WHICH ERASES STORED FREQUENCIES!], switch on while depressing 2-9-MANUAL. This programs all channels to test frequencies. The first thing I found was the ability to select U.S. or European band coverage, through a jumper on the CPU board. Installing this jumper (normally missing in the U.S.) changes the VHF-low frequency range from 29-54MHz to 66-88MHz. This looked very much like what I wanted for at least some of the TV audio reception. But it sounded like garbage, then I found out about WFM/NFM... So I removed this mod (I don't know of any frequencies in that range that would be useful). I looked through the service manual some more, and found that there were 3 pins on the processor that appeared to be inputs (from the test voltages given in the manual) yet were not used or given any other designation. I grounded each one of these pins, as I did with the European mode jumper, and tested the results. Only one of them made any difference, and it too is probably useless. What it did was to change the VHF-high frequency range from 136-174MHz to 118-174MHz. This extends the frequency coverage into the aircraft band, but this band is AM, and this radio does not have any AM detector circuitry (as far as I know). I was hoping that some magic pin would enable 16 channels (as on the similar mobile PRO-2025), but I couldn't find one. There is the possibility of more keys being added, as the scan matrix is 3x8, but only 16 keys are used (8 more could be added). The PRO-2025 has 2 more buttons, PRIORITY and WX (weather), and both of these features would be nice. Maybe someone else has some ideas? I was thinking of getting the PRO-2025 service manual, to see the differences, but I may just get a better scanner and be done with it :-) If anyone out there can come up with more modifications or information about this scanner, please let me know. There are quite a few of us out there that have simple scanners like this, and we would like to get more out of them. Not all beginners go straight to a PRO-2006, after all :-) THE MOD: European band selection: 1. Add a jumper to the digital board, connecting the empty pads near the upper left corner of the IC when looking at the board from the component side (display up/speaker down - facing away from you). When completed you should be able to power up and enter frequencies in the 66-88MHz range, with frequencies in the 29-54MHz range resulting in E(rror). Note, it should be possible to place a small switch on this jumper so that the unit can change from European to US modes (probably only when powered off). Once a frequency is entered into memory, it can be received no matter what bands are enabled. FM "Air-band" coverage: 2. Add a jumper between pin 67 of the microprocessor and ground. Pin 67 is one down from the pin connected to the pad used in the European band selection, it is the third from the top on the left side of the chip. Ground can be obtained at the opposite side of the European band jumper pad. Be very VERY careful while soldering to the pins of the surface mount chip, and have a VERY fine soldering iron tip. Once the jumper is in place, frequencies can be entered in the 118-135MHz range, and no other range is lost. If you think I take any responsibility for any errors on your part (or on my part for that matter), you have another thing coming. No warranty is expressed or implied. Use at your own risk. -- { Riyadth Al-Kazily riyadth@hpdmd48.boi.hp.com riyadth@hpbs1904.boi.hp.com } { (208) 323-4987 | When am i going to have time to use all this } { Boise, Idaho | stuff I'm collecting? More important, how can } { DoD #295 1983 BMW R65 | I get more stuff? Amiga 500+ (+ stuff, that is) } Copied from the QRZ! Windows Ham Radio CDROM