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QRZ! Ham Radio 18
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QRZ Ham Radio Callsign Database - Volume 18.iso
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pro38.txt
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2001-11-01
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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: <ByrCr7.Mvy@mail.boi.hp.com>
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) }
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