Subject: PRO51 MOD

There is an interesting test mode in the PRO-51 that, 
combined with the direct search feature of the scanner, lets 
you pick up out-of-band frequencies. You will have full 
access to the 66-88 Mhz ranges as well as the cellular base 
range of 869-896 Mhz.

Actually, there are several test modes in the PRO-51 (most of 
these comments should be true for any Uniden-made Radio Shack 
scanner, such as the PRO-46). I'll describe them first and 
then how to take advantage of one of them to get the 
restricted frequencies.

There are three data test modes. These modes completely 
destroy any frequencies you had programmed into your scanner, 
so it's best to use these techniques before you program your 
scanner. If you have already programmed it, you'll have to 
decide if these new capabilities are worth reprogramming.

TEST MODE 0. Clear the scanner.
--------------------------------
A well-known method of clearing the scanner to all zeros is 
to hold down the 2 key, the 9 key, and turn on the scanner. 
All frequencies will be lost.

TEST MODE 1. Fill channels 1-25 with test frequencies.
-------------------------------------------------------
Press the 2 key, the 9 key, the L/Out key, and turn on the 
scanner.

This fills channels 1-25 with these frequencies:

 1       30.050
 2       40.840
 3       49.900
 4      138.150
 5      162.400
 6      173.225
 7      406.875
 8      453.250
 9      511.9125
 10     108.500
 11     118.800
 12     127.175
 13     135.500
 14      66.450*
 15      76.825*
 16      87.425*
 17     157.800
 18     482.3625
 19      29.000
 20      54.000
 21     806.000
 22     857.200
 23     888.96*
 24     911.500
 25     954.9125

* indicates not within the PRO-51's normal coverage. More on 
how to use these in a minute.

TEST MODE 2. Fill channels 1-17 with test frequencies.
-------------------------------------------------------
Press 2, 9, Manual

Fills channels 1-17 with these frequencies:

30.00, 40.00, 50.00, 140.00, 155.00, 170.00, 410.00, 460.00, 510.00, 54.00, 
109.00, 118.00, 127.00, 135.00, 810.00, 860.00, 950.00.

There is also a display diagnotic mode.

TEST MODE 3. Display Test. 
-------------------------------
Press 2, 9, BAND or 2, 9, MONI.

This put the display in test mode. Every annunciator and 
every digit element is turned on in a scan from the left side 
of the display to the right. To keep this test mode 
continuous, release the buttons before the first scan 
finishes. This mode does not affect stored memory. Press any 
key to exit this display mode.

Now, if you've decided to try test mode 1, you will find 
several out-of-band frequencies stored in your memory 
channels. Channels 14-16 hold frequencies in the blocked-out 
66-88 Mhz range, and channel 23 holds a frequency in the 
blocked-out cellular base range. Once you have these 
frequencies stored in a memory channel, the PRO-51's direct 
search feature will let you search though these ranges. In 
the cellular band, the scanner searches in the correct 30 Khz 
steps.

You don't have to keep these frequencies in the channels they 
were stored by the test mode. You can move them to any 
channel in the scanner. HereUs how.

First move the frequency to a monitor channel:

While on a channel with one of these frequencies, open 
squelch completely. Press direct search button, either up or 
down. The direct search button puts the scanner into search 
mode and the open squelch holds the frequency. Then press the 
Monitor button. The frequency is now in the monitor channel 
indicated in the display. 

Now you can move it to any regular memory channel in the 
scanner:

Enter the channel number
Press PROG
Press MONI
Press the number of the monitor channel if the proper channel 
is not displayed
Press E(nter)

The frequency is now permanently stored in the memory 
channel. You can do a direct search from this memory channel 
at any time.

The 66-88 Mhz range mainly covers TV audio. However, there is 
a strange phenomenon concerning TV audio and the PRO-51. 
Channels 4, 5, and 6 fall within the 66-88 Mhz range (71.75 
Mhz, 81.75 Mhz, and 87.75 Mhz respectively), yet the PRO-51 
will not pick up the audio frequency while searching in this 
range. However, TV channel 2 audio is at 59.75 Mhz. When you 
add the intermediate frequency of 21.6 Mhz, you get an image 
of the TV channel 2 audio appearing at 81.35 Mhz. This does 
come in, although raspy, since the PRO-51 is receiving in 
narrow FM mode while TV audio requires wide-band FM mode for 
proper reception.

I'd be interested if anyone can verify that any of these test 
modes work on the PRO-46 or any other Uniden-made Radio Shack 
scanner.

Howard Bornstein

CompuServe 76174,637
Internet: 76174.637@compuserve.com
--------------------------------------------------------------------
Piran Mohazzabi
piran@freenet.fsu.edu


From: moy@xp.psych.nyu.edu
Newsgroups: rec.radio.scanner
Subject: PRO-51 Mod: Shorten squelch tail
Date: 20 Sep 1994 20:34:06 -0500
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Sender: nobody@cs.utexas.edu
Message-ID: <9409210139.AA07611@xp.psych.nyu.edu>
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Hello fellow scanbots,

Radio Shack PRO-51: Modification to shorton squelch tail

This change was performed successfully on a unit coded "11A3."  The
CPU in this unit was marked "Uniden UC1581."  Use the following
information at your own risk!  Neither I nor my employer are
responsible for any damages you may incur from this information!

Orientations are with the set flat on a work surface, LCD display 
facing down, with antenna BNC and knobs facing away from yourself.

As with any electronic instrumentation, remove all power and take 
all necessary precautions to prevent damage from electrostatic 
discharge (ESD).  This modification requires fine soldering and
familiarity with surface mount devices.

CAUTION:

Be aware that parts of the circuitry will *still* be powered!
There is a capacitor on the digital board that keeps the channel 
memory alive.  This capacitor may contain enough energy to damage 
the electronics should a short occur.

Parts required: One 1/10th watt carbon resistor, 100K to 220K.  Value is
not critical.  A lower value shortens the time the squelch remains open
after incoming signal stops.  The resistor should physically as small
as possible.

Opening Case

Fortunately, this set is very easy to open.  Open battery 
compartment and remove batteries.  Remove four screws: two 
straddle the sticker on the back of the cabinet, two others at the 
upper part of the battery compartment.  There are two small 
plastic detents at the floor of the battery compartment.  They are 
directly downwards from the "-" and "+" legends, which are molded 
on an extension of the removable back.  These detents will need to 
be unhitched to allow the back to separate from the front.
Pull back off gently.

Remove RF board

The RF board is attached to the top panel, which contains the 
volume and squelch controls and the antenna connector.  At this 
point, the board is essentially free and will separate from the 
rest of the set when the header connector at the lower right is 
pulled apart.  This header provides electrical connections between 
the two boards.  Lift the RF board straight out, and set the rest of the
radio aside.  Flip RF board over, keeping BNC pointing away from
yourself.

Add resistor

Refer to the ASCII diagram below.  Bend one of the resistor leads close
to the body of the resistor so that the resistor forms a hairpin shape.
Trim leads and solder the new resistor in parallel with the chip
resistor marked "105."  The latter is positioned between the two
surface-mount IC's towards the bottom of the RF board.  Press the new
resistor parallel to the circuit board, making sure there are no
shorts.

                   +------------+
         [101]     |            |
                   |            |
         [684]     |  NJM2090V  |
                   |            |
         [224]     |            |
                   +------------+
         [   ]   [   ]            [  || ]

         [225]   [105]              [123]
                 |   |
                 |  +-+
                 |  |R|   <---add resistor: 100K - 220K
                 |  +-+
                  \_/       +------------+
                            |            |
                            |            |
                            |  TK11900M  |
                            |            |
                            |            |
                            +------------+


Thanks to Bob Parnass for clarifying the nature of the "squelch tail"
problem and for inspiring me to figure out this modification.

Moy Wong (moy@xp.psych.nyu.edu) Dept. of Psychology, New York University