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TUCoPS :: Radio :: pro43faq.txt

Radio Shack Pro-43 Mods Frequently Asked Questions

                     Radio Shack PRO-43 Modifications FAQ

        1.  Introduction
        2.  Which units can be modified for extended frequency
        3.  Companies that will modify the PRO-43 for extended
               frequency reception
        4.  The modifications
              extended receive (original mod + solderless)
              keypad beep delete
              improved audio
              attaching an S-meter
              400 memory channels
        1.  Introduction

        Because there is  a continuing  demand for  it, this  mini-FAQ
        about PRO-43  modifications will  be  posted every  two  weeks
        until there is demand for its  removal.  In large part, it  is
        the   file   PRO43.MOD    from   pub/hamradio/mods/tandy    at .

            The FAQ now includes mods for

                    (1) extended receive (original mod + solderless)
                    (2) keypad beep delete
                    (3) improved audio
                    (4) attaching an S-meter

            There is also a mod for 400 memory channels, but, to quote
        its author, it is very  complicated, should only be  attempted
        by someone with moderate  to advanced electronics  experience,
        and is not for the faint of heart or the "weekend technician."
        A brief description is  included at the end  of this FAQ.   If
        the mod were  included in its  entirety, the size  of the  FAQ
        would be increased four-fold.
        2.  Which units can be modified for extended frequency

            Note:   In  the  United  States, it  is  against  the  law
        (Electronics Communications Privacy  Act of  1987, public  law
        99-508, amended  1994  by public  law  103-414) to  listen  to
        cellular or cordless telephone communications.  However, it is
        not illegal  to  own equipment  that  can receive  or  can  be
        modified to receive such communications, even though it became
        illegal as of  April 1994 to  manufacture or import  equipment
        that could be easily modified by the user to receive  cellular
        communications.  Equipment manufactured before the cutoff date
        can continue to  be sold  until stocks are  exhausted.   While
        businesses  are  forbidden  from  importing  cellular  capable
        scanners for resale, the question  has been raised whether  an
        individual can legally import such equipment not intended  for
        resale.  The issue is not explored here.

            Which PRO-43 units can  be modified for extended  receive?
        Units sold  in the  US and  Canada can  be identified  by  the
        following scheme

                                Modifiable  |  Nonmodifiable
           serial number         no A in #  |  begins with A
           FCC-ID                AA020-300  |    AA020-300A

        Inside the battery compartment is a paper label containing the
        date of manufacture in the form "month A year".  For  example,
        5A3 is May, 1993.  The cutoff date after which units could  no
        longer be  modifiable is  April, 1994  (4A4).   So far,    the
        earliest reported date of manufacture of a nonmodifiable  unit
        is 3A4 (March,  1994).   [There have  been *no*  reports of  a
        modifiable 3A4 unit.]

            It has been reported that some units currently being  made
        for  sale  overseas  can  be  modified  for  extended  800 MHz
        reception.  However, it is  not known whether this applies  to
        all overseas  units or,  if not,  whether there  is a  way  to
        distinguish modifiable units from nonmodifiable units.

            The PRO-43 was  produced under  two brand names.   My  3A3
        unit carries  the Realistic  name; my  12A3 unit  carries  the
        Radio Shack name.  At the moment, it is not known whether this
        represented a changeover or  whether both types were  produced
        side-by-side for a time.  It  is also not known whether  their
        electronics are different.

            There are no software modifications for the PRO-43.  It is
        not possible to  extend the  frequency range of  the radio  by
        pushing  buttons  on  the  keypad.    Such  modifications  are
        possible with other models, such as the PRO-51, but *not* with
        the  PRO-43.    The  PRO-43,   made  by  GRE  (General   Radio
        Electronics) of  Japan, is  one of  Radio Shack's  few  triple
        conversion units.  Radio Shack scanners with software mods are
        double conversion units made by Uniden.

            Modification procedures for other radios are available  by
        anonymous  ftp   from   the   pub/hamradio/mods/<manufacturer>
        subdirectories at

            There is  some  debate  about  whether  step  (5)  of  the
        extended receive modification is worthwhile.  According to Bob
        Parnass, from his "Improved Audio Mod", below:

             "Now that I have a schematic, I see that the  European
             version  of  the  PRO-43   has  different  coils   and
             capacitors in  the low  (mid) band  front end  filter.
             That explains why the 75 MHz sensitivity isn't stellar
             after adding diode D3 to enable 30-88 MHz coverage."

            So, if you trash the diode in step 4 or want to quit while
        your ahead, don't  lose sleep  over it.   On  the other  hand,
        quoting (Ray Reese),

             When I purchased my PRO-43 and did the mod for  adding
             54-88 Mhz, using the removed cell. diode, I wanted  to
             be able  to listen  to the  sound carrier  for the  tv
             channels 2-6  as well  as the  72-76 Mhz  band. It  is
             worth the trouble to  make the mode  and it does  work
             well in my area, despite not having the correct  coils
             for that band area. Do the mod anyway, but [if  you've
             trashed your  original  diode],  use  a  1N4148  fast-
             switching diode.  Perhaps a  1N914  might do  the  job
             also. They can  be found  at Radio Shack  for a  cheap

        3.  Companies that will modify the PRO-43 for extended
               frequency reception

            If you'd  rather  not  do the  modification  for  extended
        frequency reception  yourself,  Cellular Security  Group,  106
        Western Avenue, Essex, MA 01929 (508/768-7486) will do it  for
        $40, which includes insured UPS return postage.  However,  CSG
        will not move the diode to extend the low band to 88 MHz; they
        only remove the diode to unlock the 800 MHz frequencies.  When
        CSG is mentioned  on the  net, two types  of comments  follow:
        testimonials from satisfied customers and comments from  those
        with the technical skills claiming that the service seems high
        priced for just removing the diode.  But, there have been *no*
        reports of shoddy work or  damaged radios.  (They've  modified
        two of mine.)  Units are processed within 24 hours of receipt.

            Grove Enterprises'  newly advertised  Repair Service  will
        perform the mod for $40 plus shipping.  They will move (rather
        than just remove) the diode in units that can benefit from it,
        but state  that there  is no  way to  tell whether  the  diode
        should be moved without looking  inside.  They claim that  the
        determination can not be made from the serial number,  FCC-ID,
        or date of manufacture.   For further  details, call Grove  at
        704/837-7081.   In order  to get  a unit  modified, a  service
        order number must be obtained from the same telephone  number.
        Packages without a SO# will be refused.
        4.  The modifications

From: (A. Ray Miller)
Summary: cellular (870-890 MHz) and low band (51-88 MHz) restoration for PRO-43

A few people have mentioned the cellular mod for the PRO-43; it turns out
you should not remove but MOVE the diode.  Doing so allows cellular coverage as
well as low band (up to 88 MHz) coverage.

Acknowledgments to Grove Enterprises; this information came from them.
They are selling the PRO-43 for $300 which is $50 less than Radio Shack.
I have no connection with them other than as a satisfied customer.

        Cellular Frequency Restoration and Low Band Expansion

Note: It is not lawful to monitor cellular or conventional mobile telephone

The following procedure requires familiarity with microcircuit soldering and
will violate your warranty.  Grove Enterprises assumes no liability resulting
from its attempt, nor will accept the modified scanner for return under any

TOOLS NEEDED: Fine point, low power soldering pencil; solder wick or a
desoldering tool; pointed awl, hemostats or pointed tweezers; small Philips
screwdriver; solder.

1) Remove the battery, antenna and back cover (held in place by four screws).

2) Remove the six screws holding the top circuit board in place.  Carefully
unsolder the two antenna connections from the board.  Bend the antenna ground
tab fully up from the board.  Carefully lift the board, unplugging the black
connector at its base, and lay the board out of the way on its bundle of
colored wires.

3) Remove the two screws from the next board and lift it, carefully unplugging
the white connector at the bottom of the board.  Lift it up and lay it aside on
its brown wire (which can be unplugged if necessary).

4) Unsolder and remove the metal shield from the final board, revealing the
microprocessor; note the row of diodes labeled D1-D5 above it.  Only diodes
D1, D2, and D4 are present; assisted by a pointed tool, unsolder and remove D4,
the lone diode (this restores cellular frequencies which will be searched in 30
kHz steps).

5) Resolder the removed diode carefully into position D3 to extend low band
coverage to 88 MHz.

6) Reassemble the boards, paying particular attention to the alignment of the
plugs.  Test the radio by entering any frequency between 870 and 890 MHz
(cellular) and 51-88 MHz (low band).

A. Ray Miller |
    From:   IN%""  2-FEB-1995 17:55:07.31

    BTW, I did something similar [to the mod that follows] but MUCH
    easier...  No soldering, removing antennas, PCBs, etc..

    Just open up the Pro 43 and look down on the bottom PCB from where the
    batteries usually lie.  You'll see the diodes there.  Simply take an
    xacto knife and and break the solder on the D4 diode (left-most on
    mine) on the side facing you. I just cut back-and-forth for a bit.
    Once the solder (it's surface mounted) is weak enough, I just bend up
    the diode a bit from the PCB.  Presto.  I left mine hanging on the one
    side with solder. If you continue to work it a bit, you can probably
    remove the whole diode.

    From: (Jason G. Springel)
    Subject: MODing a Pro-43 without soldering

    I just purchased a new Pro-43 to replace my Uniden 200XLT after reading
    many of the praises for the Pro-43 on this newsgroup.  I decided to try
    and MOD it, but don't have a lot of experience with a soldering iron.
    After examining the scanner's innards, I found it was quite easy to
    "fix" with nothing more than a minature philips screwdriver and some
    small needlenose pliars.

    ************ Standard Discalimer from other MODs:

    1-It is against the law to monitor cellular or mobile telephone calls.

    *****2-Procedures outlined below [DO NOT] require knowledge of
    microcircuits, soldering and assembly techniques.

    *****3-You will [NOT] need a low-wattage soldering iron, solder and
    other various tools to help in the procedure.

    4-The following procedure will void your warranty.

    Here is my new MOD:

    Step 1

    Remove the battery, antenna, and back cover which is held in place by
    four screws.  Place the scanner keypad-side down on your working surface.

    Step 2

    Remove the six screws holding the top circuit board in place.

    Step 3

    Using a VERY small screwdriver (I used one from a Radio Shack kit),
    remove the two screws from the lower circuit board.  Looking down at
    the unit, you will see that the screw on right side of the lower
    circuit board can be easily removed.  Remove the screw on the left side
    by by sliding the screwdriver between the top circuit board and the
    metal frame which holds the two boards together.

    Step 4

    With these two screws removed, you can now lift the entire top panel
    (antenna, volume, and squelch knobs) along with the top two circuit
    boards as one unit.  The two circuit boards will be connected to the
    final circuit board (the one attached to the front section of the
    scanner) by several wires.  Simply set the top panel/circuit boards
    alongside the front section of the scanner and you can leave these
    wires connected.

    Step 5

    The microporcessor is located under the large metal shield on the final
    board (the front section of the scanner with the display and keypad).
    If you look under metal shield from the side closest to the bottom of
    the scanner, you should see the row of diodes labeled  D1-D5.

    Only diodes D1, D2 and D4 should be present.

    Use a small pointed tool to break off D4. You actually don't have to
    remove it completely (unless you want to use it to restore additional
    frequencies as explained in other MODs), you can just lift one side so
    it dosen't make connection and then put a small piece of tape or heat
    shrink over it, so it won't. Make sure it's not lifted to high or the
    boards will not fit.

    This will restore Cellular Frequencies in 30 kHz steps.

    Step 5

    Reverse the process to replace the top panel/circuit boards and the two
    screws that connect the lower circuit board.  Replace the 6 screws from
    the top board.  Replace the cover, etc.....

    ...the diode positions on the cpu board, of which only three are
    filled look like this.  Where  X equals a diode soldered in place.

    D5 D4 D3 D2 D1

    O  X  O  X  X                 Normal configuration

    O  O  O  X  X                 Cellular modification(D4 removed)

    O  O  X  X  X                 Lo-Band modification(D4 in D3's place)

    These directions were based on an original MOD design whose origins I
    do not know.  My thanks go out to the original author of that MOD!
    Hope this helps those of you who do not own a soldering iron!
Date: 19 Aug 92 16:51:08 GMT

Here is my keypad beep delete mod for the RPO-43:

1. Remove battery.
2. Remove back cover (4 screws).
3. Remove top board (6 screws, desolder two antenna connections and bend
   antenna ground lead up out of the way). Be careful of black connector at
   bottom of board. Flip board over and lay aside (wire connectors need not be
4. Remove middle board (remove 2 screws and wire connector). Be careful of two
   multi-pin connectors along underside of board. Set middle board aside.
5. Locate 10 pin connector on side of bottom board (labeled CN3). Note that one
   end of connector has pin 10 labeled as such. Count back to pin 6 and bend
   pin 6 ninety degrees towards the large RF shield. Make sure the bent pin
   clears the RF shield.
6. Reassemble and your done OR do the cell mod since you are so close.

Have fun. Gary Ross               >usual disclaimer>
Subject: Improved audio for the PRO-43 portable scanner
From: (Bob Parnass, AJ9S)
Date: Wed, 2 Dec 1992 01:15:35 GMT


                  by Bob Parnass, AJ9S

     The Radio Shack PRO-43 scanner audio is too bassy.1 The
     lack of treble makes it difficult to hear the PRO-43 in
     noisy situations, especially while listening in  a  car
     or  truck.   Louis Shirley sent me a schematic and sug-
     gested I remove C341, a tiny 0.015  ufd  surface  mount

     I'm glad to report that  removing  C341  made  a  great
     improvement.   The  audio  is  now much "crisper," more
     like the Uniden 200xlt, although  still  not  quite  as
     loud.   Turning  the  volume control up still overloads
     the PRO-43's small, internal speaker, but there's  less
     need to do that once C341 is removed.

     The PRO-43 contains 3 printed circuit boards,  and  the
     middle  (second)  board  contains  the audio circuitry.
     Finding C341 is difficult, as it is neither marked with
     a  value nor a component designation.  It is located on
     the foil side of the  middle  board,  under  IC304,  an
     LM386 amplifier IC.  C341 is in parallel with, and phy-
     sically next to, R350 (33,000 ohm).  R350  is  slightly
     larger than C341 and is marked 333.  Both R350 and C341
     are connected between pin 2 of the LM386 and ground.

            A Note About 50-88 MHz Reception

     Now that I have a schematic, I see  that  the  European
     version  of  the PRO-43 has different coils and capaci-
     tors in the low (mid)  band  front  end  filter.   That
     explains why the 75 MHz sensitivity isn't stellar after
     adding diode D3 to enable 30-88 MHz coverage.


 1. See "PRO-43 Product Review," by Bob Parnass, AJ9S, in
    the November 1992 RCMA Journal.

Bob Parnass, AJ9S  -  AT&T Bell Labs  - - (708)979-5414
Subject: S-Meter for PRO-43
From: (Michael Schuster)

Found this on the Fidonet scanner echo:

=====begin quoted text=================

   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

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      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)

======end quoted text====================

_______________________________Mike Schuster________________________________
NY Pub. Access UNIX/Internet: | 70346.1745@CompuServe.COM
The Portal (R) System: | MCI Mail,GEnie: MSCHUSTER
From: (LORD BB)
Subject: PRO-43 w/400 CHANNELS HERES HOW!


Brett Bennett  4/12/94
Copyright 1994 B&D Electronics All Rights Reserved


 The following document details two enhancement modifications that are
possible on the Radio Shack PRO-43 scanning radio.  The first modification
doubles the factory standard memory capacity, allowing you to enjoy an
additional 200 channels of memory, plus 10 more monitor memories.  After
completing the first modification, it is a fairly simple matter to add a 7 to
10 second delay feature to the LCD back-light lamp circuit.  I designed and
performed these modifications on my PRO-43 and they do work.  As I understand
it, there (has been/is being) presented in WORLD SCANNER REPORT a similar
memory expansion.  I have not seen this modification and for all I know it is
a better way of doing it. What is presented  is a 'clean-room' design of my
own that to the best of my knowledge is the only one to also offer a time-
delay for the LCD back-light. Having said that, let me say:


 The procedure described below is very complicated, and involves the soldering
and desoldering of very tiny components and the cutting of printed circuit
board traces.  While the procedure is not irreversible, it will leave
permanent scars inside your scanner.  It should only be attempted by someone
with moderate to advanced electronics experience.  I don't think it should be
attempted by, to quote someone else, a "weekend technician."  If as you read
through this you feel intimidated by the jargon and required procedures or if
an electronic schematic looks like a strange piece of modern art to you, then
this might not be the 'mod' you are looking for.  The following document will
assume you have obtained the materials listed below, especially the Service
Manual, and you have studied the circuit in some detail.  I will not describe
in great detail where every component is or where every solder point on the
logic board should be placed.  Having the Service Manual, and having studied
the drawings therein will allow you determine to where it is I refer.


1 - PRO-43 Service Manual.  (Tandy Parts # MS-2000300 - approx. $6.00)
1 - CD4053 -  Triple - SPDT analog switch - Surface mount  package  (DigiKey
     #CD4053BCM-ND - approx. $1.50)
2 - 93C67 EEPROMs     (Tandy Parts # MX-8050 - approx. $13.00/each)
1 - 100k x 5 resistor network.  Common lead type.  (DigiKey # Q5104)
1 - UN2111 PNP transistor (Q1 on Logic PCB.  Tandy Parts  # )
1 - 1 uF 16v capacitor.
1 - 10 MOhm 1/8-1/16W resistor.
Wire wrap wire-30 gauge.  (Radio Shack)
Grounded soldering iron with approx.  1/32" tip or smaller.
Desoldering Equipment.
Digital Volt Meter.  (Used to double check your VCC and Ground connections,
  pre-check switching assembly)
Utility knife with fresh sharp small blade.  (Needed to cut traces.)
Strong hand held magnifying lens.  (Needed to check solder joints.)
+5-10 Volt bench power supply.  (Used to check switching assembly.)
Anti-Static work place and grounding wrist band.
Very fine needle nose pliers, wire cutters.

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