THE NL3ASD MODIFICATION FILES - HAM RADIO MODIFICATIONS - PAGES L TO SHOMEPAGE

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) }


SOURCE: The QRZ Windows Ham Radio CDROM



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