Skip to main content

Full text of "Bill Cheek - World Scanner Report"

See other formats


Publisher/Editor: II. D. Cheek. Sr. aka “Or. tmrm>rtis" V1N1<: Noveaber-Deceaber. 1991 

THE WORLD SCANNER REPORT 

A Journal of VHF-UHF Scanner Technology i Engineering 


Published at: COHHtronics Engineering; PO BOX 262478; San Diego, CA 9219$ Copyright (c) 1991 (All Rights Reserved) 


GROSS IGNORANCE & SHEER STUPIDITY 

Humble pie. The subscription blank that appeared in the 
last few issues was thoroughly confusing with good reason 
since it was designed for new subscribers with no thought 
given to renewals. The blank on the inside of the back 
page has been revised to be easier to understand and fill 
out. Back Issues are under one heading; current subs are 
under a separate one now. If, for any reason, you feel 
that you were shortchanged by the confusion, let us know 
and we'll make it right. Standard policy is to issue a 
refund for overpayment, but let us know if that's not 
satisfactory. The new sub blank & prices are current and 
supersede all others. Apologies for imbecilic idiocy. 

LAST CALL TO RENEW FOR 1992 

Check the Expiration Date on your mailing label; if it 
says "Nov 91", this will be the last issue you'll receive 
until you renew. A fluorescent color will highlight that 
part of your label as a reminder of impending expiration. 
1992 is shaping up to be a great year for unleashing the 
power of your scanner. You won't want to miss out! Renew 
right away before you forget! Thanks to those who have 
renewed early. Cindy, our Administrator, is delighted to 
have the work spaced out instead of piled up all at once. 

THIS IS THE LAST ISSUE OF 1991 

This is the 10th and last issue of 1991. The WSR is 
published 10 times per year to allow for Staff Holidays 
and uninterrupted periods of R & D for coming issues. 
January, 1992, begins our second year with V2N1 to be 
mailed on or around Jan-1, but slight delays caused by 
the holidays are to be expected. The mails will be slow 
(and so will we). By February, we’ll be back on track to 
mail each issue during the last week of the month. Thank 
you for a great 1991. Your support and acclaim were the 
booster stages that put us into low orbit. Next year, 
the moon; and then the planets and the stars 

WANTED TO BUY: A CHEAP COMPUTER 

We're looking for a very cheap IBM/clone MSDOS computer, 
either 8088 or 80286 based. Minimum requirements are 
640-k RAM, one or more floppy drives; monochrome; one 
serial and one parallel port. Desirable options might 
include a hard drive, modem, CGA/VGA , etc. Our budget 
for 1992 includes a serious 386 or 486 computer but a 
rock-bottom priced model of the above description is 
needed NOW so that we can begin the final phases of 
research on Computer Interfaces for the PRO-2004/5/6. 
R&D is always expensive, so costs have to be kept down. 
If you have or know of a very cheap computer available, 


please speed your offer immediately. Serious offers with 
our minimum needs will be considered. For those who 
don’t know, we've been Apple-based for many years while 
IBM & MSDOS passed us by. It's clearly evident that an 
Apple Interface for scanners won’t be well received; 
hence our need for a simple and inexpensive IBM/clone 
developmental machine. 

THE LATEST ON COMPUTER INTERFACES 

The need for easy computer programming of scanners with 
400 or more channels is self evident now. One round of 
manually punching in 400-channels, only to discover that 
an inadvertent missed frequency at Ch-47 will be enough 
to make you see the Cosmic Light. If you’ve done the 
3200, 6400 or 25,600 Channel Mods, that Light will be 
blinding. Would you believe that computer interfacing of 
the PRO-2004/5/6 is actually "old hat" now? Two or three 
years ago a fellow advertised in "Monitoring Times” plans 
for a Commodore 64/128-PRO-2004 interface . I mentioned 
this to a digital guru, Lin Burke, who then whipped up a 
functional interface for the Radio Shack Color Computer 
II. He went on to modify it and the associated BASIC 
program for my Apple. No problem. Then came a design by 
Miles Abernathy for the Macintosh computer. We converted 
the design and its BASIC control program for my Apple. 
Lots of work and cost but it was done. Two things these 
three interfaces had in common was ONE-WAY communication 
with the scanner and a computer-specific BASIC program to 
run the interface. 

More recently comes a universal interface kit from RW 
Systems and an MSDOS-specif ic interface package including 
software from DataMetrics, Inc. The kit from RW Systems 
is promising because (1) it appears to be universal for 
most computers and (2) computer-specific software is not 
required to run it. It requires only a serial port and a 
routine telecom program for operation. DataMetrics' 
package is complete, ready to install in any MSDOS 
computer with 640-k RAM and a parallel port. While the 
DataMetrics' package works only in IBM/clones, it is 
driven by commercial software; the interface is easy to 
install and appears to be foolproof in operation. Both 
the kit from RW Systems and the package from DataMetrics' 
appear to be two-way devices in the sense that the 
computer can log and store events from the scanner. RW 
Systems’ kit appears to be functional for any of the 
PRO-2004/5/6 series, while DataMetrics specifies that 
theirs is for the PRO-2006 only. I think it is a safe 
bet that it will work just fine in the PRO-2005 and can 
be easily adapted to the PRO-2004, but DataMetrics does 
not support any but the PRO-2006 at this time. I will be 
evaluating RW Systems’ kit and the DataMetrics package in 
the coming weeks. Perhaps we will have an opinion to 



offer in the next issue. If you want specs & prices in 
the interim, contact the companies as follows and tell 
them you were referred by the "WORLD SCANNER REPORT". 

DATAMETR ICS, INC RW SYSTEMS 

2575 SOUTH BAYSHORE DR; STE-8A PO BOX 910(543 

COCONUT GROVE, FL 33133 SAN DIEGO, CA 92191 

Two of the three one-way interfaces discussed above are 
not commercial ventures so the circuits & BASIC programs 
can appear here in future issues if interest warrants. 
There may be other designs for interfaces that we'll 
publish, too, as there seems to be a wealth of info and 
interest circulating now. We will confine our main focus 
to those interfaces, commercial or public-domain, which 
give the most for the least and which require a minimum 
of effort on the hobbyist to install and operate. I have 
a feeling there will be dozens to look at in the coming 
year, so a certain amount of focus on our part will be 
necessary. A key focus will be on the TWO-WAY interface; 
i.e, one that not only programs the scanner's memory 
banks, but also which can pass data from the scanner to 
the computer for logging of active freqs, lengths of 
transmissions, dates, times, etc. To my way of thinking, 
the most important side of an interface is that which 
programs the scanner's memory banks, thereby sparing us 
the drudgery and opportunity for error. This alone will 

free up time to enjoy the benefits of our scanners. But 

if enjoyment is what this business is all about, then we 

have to look at the other side of the coin: data logging 

& processing. Half the fun of scanning is in the 

listening to what's going on, but the other half is in 
the accumulation of knowledge and understanding of radio 
communications. The side of an interface that passes 

data from the scanner to the computer for logging, 
processing and storage is the long term benefit while the 
actual monitoring is a short term benefit. Therefore, we 
will look at both sides of a scanner-computer interface 
in the coming year. Speaking of both sides, there are a 
limited number of ways to obtain data FROM the scanner, 
perhaps only two. DataMetrics found one way that might 
never have occurred to me; HB Technologies is breaking 
ground on the only other way that seems possible at the 
moment: decoding the data from the scanner's CPU to the 
LCD Display! That data stream contains most everything 
pertinent to scanning with exception of time and date. 
The trick is to decode it, since some of that data is 
superfluous and some is for the PLL circuits but the boys 
over at HB Technologies seem to have deciphered the stuff 
for the LCD Display and what's more, they’re about to 
show you how you can do it for yourself. 

A SERIAL DATA I NTERCEPTOR/DEOODER FOR THE 
PRO- 2004/5/6 CPU/LCD DISPLAY DRIVER 

By: B.Bond/HB Technologies 

This article describes in detail an actual circuit that 
can "view'' data transferred from the PRO-200X CPU to the 
LCD control ler/driver 1C. The circuit is elementary in 
nature and lends itself well to both practicality and 
cost limitations. A drawback of this approach is that 


the device (referred herein as the GBL) relies heavily on 
manual interpretation of captured data. IC’s comprising 
the GBL are described as follows: 

74HC164 - Ser ial - 1 n/Paral I el -Out (SIPO). Takes a serial 
byte of data and converts it to parallel format. 

74C14 - Hex Schmitt triggers (inverting). Inverts BUSY\ 
for use as a write pulse (W\) in addition to generating 
a read pulse (R\) at the DS2009 FIFO (below). 

DS2009 - A 512 x 9 bit First- In/First-Out (FIFO). Used to 
store the data and C/D\ flag from the CPU. 

MC14495 - Hex/7-segment decoder. Converts the hexadecimal 
data from the FIFO to 7-segment for LED display. 

Waveforms used by the GBL 

RESET - Used to reset both the uPD7225 and DS2009 . 
Generated by IC-503 (Scanner CPU) at power-up. 

BU$Y\ - Inverted and used to perform FIFO write 
operations. Generated by UPD7225 and goes high upon 
receipt of CS\ (chip select) low from the CPU. BUSY\ 
remains high for duration of byte transfer and returns 
low when the UPD7225 is ready to receive the next data 
byte. 

W\ - FIFO write pulse. Leading edge of W\ initializes 
write. Trailing edge writes data. 

SI - Serial data input from CPU. Presented to SIPO and 
clocked by SCK\. 

C/D\ - Control/Data (not) flag. When C/D\ is a logic low, 
the data transferred from the CPU is a display byte, 
whereas a logic high represents a command byte. Used 
within the UPD7225 for data routing and by the GBL for 
data differentiation. 

R\ - Read pulse for retrieving data stored within the 
FIFO. Also latches display data within the Hex/7-segment 
decoders. 

FF\ - FIFO full flag. Logic low indicates that the FIFO 
is full and no further writes may be performed. Logic 
high permits additional writes. 

EF\ - FIFO empty flag. Logic low indicates that the FIFO 
read pointer has returned to the write pointer location 
following a read operation. 

The GBL operation begins with the reset pulse from the 
CPU. Reset causes both the internal FIFO read and write 
pointers to reset to the bottom of the memory stack. 
BUSY\ goes high (driven by C$\ low) prior to data-send 
causing W\ to go low and initialize a FIFO write. 8 bits 
of data are sequentially clocked into the SIPO by 8 SCK\ 
clock pulses. The most significant bit of the data byte 
will be at the QH output of the SIPO following the 8th 


"THE WORLD SCANNER REPORT" (c) 1991; V1N10 - Nov-Dec, 1991; Page 2 



CP. Within 9-usec of the 1st CP, C/D\ will be setup. At 
this time, the data byte and flag (C/D\) will be present 
at the FIFO inputs D0-D8. After the 8th CP, UPD7225 pulls 
BUSY\ low and routes the byte to internal registers. 
This action causes W\ to go high, writing the byte and 
associated flag into the FIFO. Having transferred the 
byte, UPD7225 returns a BUSY\ high, allowing subsequent 
byte transfers. Readout of the FIFO content is initiated 
by R / pulses which present and latch the data to decoders 
which drive a dual 7-segment display. Note: C/D\ drives 
the RH decimal point of the most significant character 
and is not latched. Consequently, the flag is present 
only for the duration of the read switch depression 
before the FIFO output is returned to a high impedance 
state (release of FIFO read switch). 

Because of the rapid data rate, the FIFO is quickly 
overflowed during dynamic scanner functions (i.e. Scan, 
Search, etc). This limits the GBL user to initiating 
discrete functions, trapping the bytes, interpreting the 
data, and lastly, ascertaining what areas of the memory 
stacks internal to the UPD7225 are affected. In addition 
to the transfer speed, the fact that several bytes are 
Display, compounds the problem of automating an analyzer. 
The reason is that 9 bits are required to properly ID a 
byte and UARTs are good for only 5,6,7, or 8 bits. Below 
are example bytes used within the UPD7225: 

BYTE DEFINITION 


42 mode set command which configures the 1C as a 
quadruplexed driver. 

20 clears display RAM. 

11 enable display. 

EX 1 1 1 D4 D3 D2 D1 D0; load data pointer w/ 5 bits of 
X=Dn immediate data. 

DX 1 1 0 1 D3 D2 D1 D0; write 4 bits of immediate data 
X=Dn to the display RAM area addressed by the pointer and 
increment pointer. 

AX 1 0 1 0 D3 D2 D1 D0 , or blinking RAM addressed by 
X=Dn pointer with immediate data. Write results to same 
address, increment pointer. 

Part sources: DS2009, MC14495, Allied Electronics, 

(800) 433-5700; 74C14, 74HC164, Easy Tech; (800) 582-4044 
or Digi-Key (800) 344-4539 

This concludes an overview of mapping & decoding serial 
data from the TxD port of the PRO-2004/5/6 CPU. This 
info is provided for the benefit of those engineers and 
technical people who want to contribute to the budding 
science of interfacing the PRO-2004/5/6 to a computer. 

j EDITORlS NOTE: I do not pretend to fully understand all 

the content of this article and therefore probably cannot 
answer questions about it. You can address questions to 
8. Bond, c/o Editor , "WORLD SCANNER REPORT", and I will 

forward to him for reply. Meanwhile, check this issue 
for a schematic diagram of the GBL Data Analyzer and if 
not present, it will be included next month. It was lost 
in the US Mail as of this editing, /be] 


FEATURE PRESENTATION #1 
A TONE DECODER/REJECTOR FOR SCANNERS 

Just as the goal of the Computer Interface Project is to 
enhance the fun and enjoyment of scanning, so too is this 
neat modification for your scanner! Are you aware of the 
concerted effort and conspiracy to deprive hobbyists of 
some of that enjoyment? Government agencies and police 
departments are especially guilty of this conspiracy when 
the rascals spend millions of our tax dollars to encrypt 
their communications. It is fortunate that many of the 
conspirators can't afford the "unbreakable" DES/DVP 
encryption systems, but this doesn't dissuade them from 
taking a stab at other methods of depriving hobbyists of 
their pleasure! Take for example, the nasty, nuisance 
tones we hear on some transmissions nowadays. Some of 
these signals are computer data communications, but 
others are nothing more than pure tones sent out between 
real transmissions so as to cause scanners to lock up on 
them. What could be more obnoxious than loud, unabated 
squeals? In the space of a few seconds, any sane and 
sober scannist in full possession of his faculties will 
punch the LOCKOUT button to preserve the family peace and 
general state of mind. (Mission accomplished!) 

The Toronto, Ontario, metro police agencies were among 
the first around the world to implement "anti-scanner” 
tones between transmissions to deter routine monitoring 
of their communications. The cost was negligible; the 
effect was monumental. Who, but a lunatic, would monitor 
a 2-3 KHz piercing tone for hours on end? The public-at- 
large sure won't. It wasn't long before the radio wizards 
of Toronto designed a circuit to defeat the anti-scanner 
tones and I am pleased to offer a variant of what they 
call the "Metro Mod". I evaluated one version of the 
Metro Mod as submitted by Mervyn DeGeer and found that it 
had a few problems so I redesigned it and tested it for 
hours. With no known bugs, my Tone Decoder/Rejector (TDR) 
is offered for your evaluation and sadistic use. 

My TDR uses an LM-567 Tone Decoder chip and a few parts 
to detect a single tone of your selection. The TDR is 
sensitive ONLY to the preselected tone and ignores other 
sounds in the audio spectrum. When that tone comes in, 
the TDR quickly reacts to force a $QUELCH-$et and thereby 
fool the scanner into resuming SCAN or SEARCH. If the 
scanner is in the MANUAL mode monitoring a frequency 
which has the offending tone, the SQUELCH will not break 
until the nuisance tone disappears and a voice signal is 
present. If the scanner is SCANning or SEARCHing, it 
won't even pause on a channel that has the offending 
tone, but it will still stop and monitor any voice and 
other transmissions that don't have the preset tone! The 
tone to be rejected is set by adjustment of a trim pot, 
VR-1, until the offending tone disappears! 

There are no known liabilities or bugs in the TDR, but 
there are limitations; it's good for only one essentially 
pure and steady tone at a time which must be roughly 
between 500 Hz and 5 KHz. The TDR will not respond well, 
if at all, to warbles, repetitions, or data tones such as 


"THE WORLD SCANNER REPORT" (c) 1991; V1N10 - Nov-Dec, 1991; Page 3 



for FSK, FAX & computers. If you identify two or more 
different anti-scanner tones in use around the spectrum, 
then you'll have to use one TDR for each tone; else reset 
the one TDR for whatever single tone disinterests you the 
most at a given time. If your tone-rejection needs are 
lower than 500 Hz or higher than 5 KHz, a variation of 
the design will be necessary. Likewise, two or more TDRs 
working together may require a slight revision of a part 
of the design. For now, let’s designate my TDR solely to 
reject a single tone. If your needs are more complex, we 
can discuss pertinent revisions in subsequent issues. 

There is another situation where my TDR won't fully 
apply. Some agencies transmit a tone along WITH voice 
transmissions. Notch filters in their receivers remove 
the tone leaving only voice to the speaker. My TDR will 
not remove the tone and still allow the voice to be heard 
in this type of "anti-scanner" measure. The TDR will 
prevent the scanner from locking up on such signals, 
however. To that extent, the TDR will preserve your 
sanity even though you won't hear the voice signals. I 
would like to hear from you folks who are plagued with 
the "tone with voice" attempt at encryption, and if 
enough of you respond, I will design a notch filter to 
block such tones and still let voice through. By and 
large, the "tone between transmissions" is the more 
prevalent "anti-scanner" measure, and is for what my TDR 
is designed. Ok, let's get to work and build one. 

First, you have to select the correct TDR circuit. Refer 
to last month’s issue, V1N9, Table 2, page 6 for the 
NFM/AM chip that's in your scanner, and look in the far 
right column of that table for the type of SQUELCH Logic. 
If yours is Logic 0 when Squelch is Set, and 5,6, or 8v 
when Squelch is Broke, then select the Type 1 TDR . If 
your scanner's logic is just the opposite with Logic 5, 6 
or 8v when SQUELCH is Set, and 0 when Squelch is Broke, 
then select the Type 2 TDR . If there is any doubt on 
which TDR is for your scanner, a simple test will decide 
for you: set the scanner to a quiet channel (no signals), 
and connect a volt meter between scanner ground and the 
SCAN CONTROL pin of your scanner’s NFM/AM chip. See 
Table 1 below for the correct pin # for your specific 
NFM/AM chip. Now, set the SQUELCH control so that all 
noise is silenced, and read the voltage at the SCAN 
CONTROL pin. Then rotate the SQUELCH control so that 
static noise can be heard and again read the voltage at 
the SCAN CONTROL pin. If the first reading was 0-v and 
the second, between 5 & 8v, you'll need the Type 1 TDR. 
If your measurements were just the opposite, then yours 
is the Type 2 TDR. The PRO-2004/5/6 and most Realistic 
scanners will use the Type 1 TDR while most Uniden & 
Bearcat scanners need Type 2, but be sure first, before 
jumping in headlong. There’s not much difference between 
the two TDR's but Type 2 requires one transistor and two 
more resistors than Type 1. The TDR is easily assembled 
on perf board about an inch square. Layout is not 
critical, but follow the schematic diagram for the sake 
of simplicity. It's not complicated. 

The TDR was rigidly tested on the PRO-2004/5/6 & PRO-34 

"THE WORLD SCANNER REPORT" (c) 


scanners but it will work with most any scanner that uses 
an NFM/AM chip like we've discussed so often in past 
issues. There are 4 connections to the scanner: ground; 
+5v; and two to the NFM/AM chip, "Detector Out" pin and 
the "Scan Control" pin. Refer to last month's issue, 
V1N9, Table 2, page 6 for the NFM/AM chip that's in your 
scanner and then to Table 1 below for the Pins to which 
you'll connect the TDR: 


Table 1: TDR Connections 


NFM/AM 
Chip Type 

Scan 

Control 

Detector 

Out 

Notes 

TK 10420 

13 

9 

PRO-2004/5/6; PRO-34/37 

TK10421D-2 

13 

9 

Cobra SR-15 

TK10421M-2 

16 

11 

BC-100/200/205/855XLT 

MC3357P 

13 

9 

Realistic, Regency, 

MC3359P 

15 

10 

BC-800XLT; BC-100XL 

MC3361N 

13 

9 

Realistic; AOR 

NJM3359D-A 

15 

10 

BC-400/560/760/950XLT 


Install the Tone Decoder /Rejector board in a handy, out 
of the way place in the scanner. If you anticipate the 
need to occasionally adjust for different tones, then 
consider a regular potentiometer with an external shaft 
for VR-1. Another good idea and one which I often employ 
is to drill a hole in the front panel of the scanner and 
super-glue a trim pot behind the hole for a convenient 
but unobtrusive screwdriver adjustment. Otherwise, VR-1 
can be a trimpot on the perf board of the TDR. I suppose 
you could dispense with S-1 and let the TDR run full 
time, but if you want to be in total control of things, 
install the switch where it can be readily reached. 

The LM-567 chip is specified for a maximum of 9-volt dc 
power, but you don't want to go to the limit when there's 
no need. Most scanners nowadays have regulated +5vdc so 
use it if you can. Otherwise, the operating voltage will 
not be critical between 5-8 vdc. Connect the TDR power 
point (Pin 4) to +5v via the DPDT switch. Make sure the 
TDR board is well grounded. Solder R-2 directly to the 
"Detector Out” or "Recovered Audio” pin of the NFM/AM 
chip instead of putting it on the TDR board. Connect a 
wire from the free end of R-2 to the free end of C-1 on 
the TDR board. Solder a wire to the output (U-1, Pin 8, 
Type 1 or collector of Q-1, Type 2) of the TDR, but don't 
connect it to the NFM/AM chip’s "Scan Control" pin just 
yet. We'll first test the TDR to make sure it works. 

Preset VR-1 to one end of its rotation. Attach a volt 
meter between scanner ground and the free loose end of 
the TDR output wire. Turn on the scanner and the TDR. 
Set the scanner to a frequency that has an obnoxious tone 
that you wish would go away. The voltage at the TDR 
(Type 1) output should be equal to the supply voltage or 
aboutT volts. For Type 2 TDR's, the voltage will be 
about 0 volts. Now, slowly adjust VR-1 thru it’s range; 
at some point, that voltage should suddenly change; for 
Type 1 ' s it will drop to nearly zero volts and for Type 
2 ' s it will rise to 5-v. Continue adjusting VR-1 and the 
voltage should change back to where it was before. 



1991; V1N10 - Nov-Dec, 1991; Page 4 



TYPE 1 TONE DECODER/REJECTOR CIRCUIT 


The dropout point (Type 1) or peak point (Type 2) is the 
tone-reject point of the TDR. 

If your tests are successful at this point, then solder 
the TDR output wire to the "scan control" pin of the 
NFM/AM chip. Again slowly adjust VR-1 thru its range 
until the offending tone just disappears. Tweak VR-1 
back and forth to determine the middle of the dropout 
zone and leave it set there. Operate the scanner as 
normal with a welcome feeling of sheer relief! 

Now a bit of theory for those who want to know how this 
sucker works. The LM-567 chip is the key to it all. It 

is rather complex on the inside, but with 8-pins on the 
outside, one for ground and one for power, it is very 
easy to use. In lay terms, the 567 is a "tone decoder”, 
where the resistance between pins 5 & 6 and capacitance 
from pin 6 to ground determine the tone to be decoded. 
The equation for the tone is given as: 
j where: 

1 1 f 0 is the tone, hertz 

fo = (VR1)(C4) 1 VR1 is resistance, ohms and 

j C4 is capacitance, farads 

I 

I 

Suppose that VR-1 is set to 2 , 500-ohms and C-4 is 0.2-uF, 
then: f, = 1 / (2,500)( .2 x 10-*) = 1 / .0005 
= 2000 Hz 

Obviously, changing the value of VR-1 or C-4 will change 
the tone to be decoded. The 567 is rated for a range of 
frequencies from about 0.01 Hz to 500 KHz. For our use, 
we need only a 'range of maybe 500 Hz to 5 KHz, so VR-1 
and C-4 were selected accordingly. The Bandwidth of the 
tone decoder can be varied somewhat by the value of the 
capacitor, C-2. The smaller the capacitor, the wider the 
bandwidth. Too small of a C-2, and the bandwidth will be 
so narrow that VR-1 will be touchy and hard to set. Too 
large of a value of C-2, and the TDR will cover too much 
range and result in "falsing" or reaction to desirable 
signals. The design here is good as is but the variables 
are explained in case you find a use for it in some other 
situation. A neat chip, the 567. 

I 

VR-1 and C-4 set a specific tone to be detected. The 
audio output of the NFM/AM chip is applied to the input 
of the TDR via R-2 and C-1 to Pin 3. As long as the 

preset tone is not present, the 567 does nothing and the 

output at Pin 8 is high at about 5 volts. When the 

preset tone enters Pin 3, the 567 instantly detects it 

and changes its output at Pin 8 from high to low or 0v. 
This 2-state logic is used to discriminate among sounds. 
For Type 1 scanners, the "high" output of the TDR makes 
the scanner do nothing but act normal. When the preset 
tone comes in, the output at Pin 8 goes low to force a 
synthetic SQUELCH-Set at the NFM/AM chip's SCAN CONTROL 
pin. This forced SQUELCH-Set blanks the sound and the 
scanner will resume SCAN or SEARCH. Type 2 scanners have 
an inverse Squelch Logic, so Q-1 inverts the 567’s output 
logic to match. When the 567's Pin 8 output to Q-1 is 
high, the collector output of Q-1 is low and vice versa. 
It is as simple as that; a logic inverter. 


1 




Ckt 

Svm Description 

U-1 LM-567; NE-567; ECG/NTE-832; SK9089; R/S 276-1721 

XU-1 1C socket, 8-pin DIP; R/S 276-1995 
C-1, 3 Capacitors; 0.01-uF; R/S 272-1065 
C-2 Capacitor; 0.1-uF; R/S 272-1432 

C-4 Capacitor; 0.22-uF; R/S 272-1070 

C-5 Capacitor; 2.2-uF; R/S 272-1435 

R-1 Resistor; 10- k; R/S 271-1335 

R-2 Resistor; 47-k; R/S 271-1342 

VR-1 Variable resistor; 10-k; R/S 271-282 (Note: this 
unit cannot be super glued behind a panel hole as 
recommended in the text; a different style needed. 
S-l Df>or SWITCH 

S L K 


S-l 

o 


Lc 


-> +5V ifj sry»*/,A/e R(+5to+M 


OFF ON 

o o—o 






C-3 _L 




4 5 

8 

,, . 6 < 


U-l 

2 

L/T\ 1 ' 


S67 

3 

7 . 




Fc/t 

tf/M€/Z To A/C S 





fit MS FoH /Of ft 
SCA*JV£/t 


aw or»e/ts> 


TYPE 2 TONE DECODER/REJECTOR CIRCUIT 
Additional parts required: , 

Ckt Wb-ftb 

Svm Description 

Q-1 Transistor, NPN; 2N2222A or equiv; R/S 276-2009 
R-3 Resistor; 4.7-k; R/S 271-1330 

• R-4 Resistor; 10-k; R/S 271-1335 


OfF 




S-l 



+5 v scan /J&R (+5To+8d) 



rmm 

LJ 


1 





pT . 





TbUSS- 


T ScF IcJCT poft '") 5Xi B o/a/ 

fi/FS poft /Of ft C Foft PftO-lMySl 
ScAxJdeft . j OTHcftS 


"THE WORLD SCANNER REPORT" (c) 1991; V1N10 - Nov-Dec, 1991; Page 5 






FEATURE PRESENTATION #2 
DATA/TONE SQUELCH CIRCUIT FOR PRO- 2004/5/6 

Here's an exceptionally great mod to let the PRO-2004/5/6 
recognize worthless computer data and other single or 
multiple tore signals and then resume SCAN or SEARCH 
within a second or so after locking up on these types of 
signals. This mod may resemble the Tone Decoder/Rejector 
described above, but they're totally separate circuits 
for different applications. The Data/Tone Squelch can 
serve in a limited capacity as a Tone Decoder/Rejector, 
(i.e, a "Metro-Mod), but it's really for a broader need 
to discriminate against many forms of non-voice signals 
and not just a specific one like the TOR above. Another 
difference is that the TDR will work in most any scanner 
whereas the DATA/TONE SQUELCH is only for the PRO-2004, 
PRO-2005 and PRO-2006. I am researching ways to apply it 
to other scanners, so don't despair if you don't have a 
PRO-2004/5/6 at the moment. 

The biggest impact of the DATA/TONE SQUELCH is that you 
don't have to lockout the Trunked Data Channels anymore 
when you're monitoring 800 MHz SMR systems! (The data 
channels change every day, anyway, which complicates the 
manual LOCKOUT methods on a long term basis.) A scanner 
equipped with my DATA/TONE SQUELCH (DSQ) circuit refuses 
to lock onto those obnoxious signals as well as cellular 
data; most continuous tones; DES/DVP; Improved Mobile 
Telephone Service (IMTS) tones and most other non-voice 
signals including digital pagers. My DSQ will even 
discriminate against static! In other words, my DSQ 
discriminates against all but two kinds of signals: voice 
and silent or dead carriers! The latter is ok because 
the PRO-2004/5/6 SOUND SQUELCH (SSQ) takes care of silent 
signals. In fact, my DSQ works with the SSQ but is 
independent of it except that the SOUND SQUELCH button on 
the front panel activates/deactivates both functions. 
Two SPST switches provide independent control of SSQ and 
DSQ! Construction/installation of the DSQ are simple and 
within the ability of most hobbyists. 

STRONG ADVICE: You should have the Service Manual for 
your scanner before doing this modification. Order it 
from any Radio Shack store or directly from Tandy 
Rational Parts Center; (800) 442-2425. 

CONSTRUCTION OF THE DATA SQUELCH CIRCUIT 

Build the DSQ circuit on perf board about 1” x 1 1 /< ” 
though smaller is ok if you are good at micro circuits. 
Refer to the pictorials of the parts layout and soldering 
plan, Parts List and Schematic Diagram. Use an 1C 
socket (XU-1) for U-1 and don't plug U-1 in until the 
board has been finished and checked for errors. Don’t 
install C-1 on the board but keep it handy for later in 
the instructions. Note that Pins 1, 6, 7, 8, 9, 10, 11, 
13 & 14 of U-1 are not used. Snip those pins from XU-1 
before inserting the socket into the board. 

Attach a stiff bare copper wire (#18-#22 ga) to the 
ground trace of the board. Loop it through the holes in 


the perf board for rigidity and then solder it to the 
main ground trace of the DSQ. Leave about 1-inch of this 
bare wire free. It will simplify installation of the DSQ 
board in the scanner. Solder a RED hookup wire to Pin 3 
of XU-1; solder a YELLOW hookup wire to the junction of 
D-1 and D-2. Solder a WHITE hookup wire to the anode of 
D-4. Solder an ORANGE wire to the cathode of D-4. 
Solder a BLUE wire to the cathode of D-3. NOTE: These 
wires should be about 6" -8" long. 

Construction and layout are not critical and can be 
varied from my suggestions which are about as simple as 
possible and involve no loops, jumpers or other weird 
wiring techniques. Make your board as small as possible, 
though, so that it won't take up too much room inside the 
scanner. You may be doing lots of modifications in the 
future and space might come at a premium. Install the 
DSQ Board in an out of the way place, though VR-1 should 
be accessible for initial adjustments. The bare ground 
wire on the DSQ Board can be soldered to the chassis or 
to a printed circuit board ground trace, thereby making 
the mount much easier. This bare wire can be bolted to 
the chassis if you don't have a heavy duty soldering gun. 
Once soldered or bolted, this stiff wire should make the 
DSQ Board relatively immobile and stable. You can wrap 
the DSQ Board with a layer of clear, plastic tape if 
there is a chance of anything shorting to it. 

PRO-2004 ONLY: Solder the (+) leg of C-1 directly to 
IC-5, Pin 14. 

PRO-2005/6 ONLY: Solder the (+) leg of C-1 directly to 
IC-5, Pin 7. 

PRO-2004/5/6 ALL: Solder the free end of the YELLOW 
hookup wire to the (-) leg of C-1. Solder the BARE 
ground wire to the chassis or a circuit ground in the 
scanner. Solder the free end of the RED hookup wire at 
Pin 3 of XU-1 to the OUTPUT leg of IC-8, the +5 volt 
regulator on the main chassis of the scanner. IC-8 is 
the same in all three scanners, PRO-2004/5/6. 

PRO-2004 ONLY: Locate CN-504 on the Logic/CPU Board, 
PC-3, and follow its wire bundle back to the top of the 
main receiver board. Locate the sky blue (light blue) 
wire that connects to the main board at the right end of 
the row of wires and desolder that wire from the board. 
(This wire comes from Pin 15 of CN-504.) Let it hang 
loose for a moment. 

PRO-2005/6 ONLY: Locate CN-3 on the main receiver Board 
and follow its wire bundle up to the Logic/CPU board. 
Locate the sky blue (light blue) wire that connects to 
Pin 4 of CN-3. Clip that blue wire halfway between CN-3 
and the Logic/CPU Board. Let the two cut ends hang loose 
for a moment. 

PRO-2004/5/6 ALL: Install two SPST switches of your 
choosing in a place of your choosing on the scanner's 
front or rear panels. For rear panel installations, 
Radio Shack’s micro-mini toggle switches, #275-624, will 


"THE WORLD SCANNER REPORT" (c) 1991; V1N10 - Nov-Dec, 1991; Page 6 



be just fine. These switches can also be put into the 
front panel, and isn’t difficult to do on the PRO-2004 
where there is plenty of room. It is more difficult on 
the PRO-2005/6 where the Logic/CPU Board must first be 
removed. (See V1N2 of the "HSR" or Vo 1 -2 of my SCANNER 
MODIFICATION HANDBOOK for how to do this.) One very neat 
choice of switch for any of the PRO-2004/5/6 is a 4, 6 or 
8-position DIP switch. The extra switch positions can be 
used for other things in due time! 

PRO-2004/5/6 ALL: Solder the ORANGE wire of the DSQ 
Board to the bottom lug of one switch. This switch will 
control the stock SOUND SQUELCH (SSQ) function, on or 
off. Solder the BLUE wire of the DSQ Board to the bottom 
lug of the other switch. This switch will control the 
new DATA SQUELCH function, on or off. Solder a bare 
jumper wire from the free lug of one switch to the free 
lug of the other switch. 

PRO-2004 ONLY: Solder the sky blue wire that was removed 
from the main board to the bare jumper wire between the 
lugs of the two switches. Solder the WHITE wire of the 
DSQ Board to the empty spot on the main scanner board 
where the sky blue wire was removed. THIS COMPLETES 
INSTALLATION: Proceed to ADJUSTMENT OF VR-1. 

PRO-2005/6 ONLY: Splice the WHITE wire of the DSQ Board 
to the cut sky blue wire that goes to CN-3 of the main 
scanner board. Splice one end of a hookup wire to the 
other cut end of the sky blue wire that goes to the Logic 
/CPU Board in the front panel. Insulate the splices! 
Solder the other end of this new hookup wire to the 
common bare jumper wire between the top lugs of the two 
switches. THIS COMPLETES YOUR INSTALLATION: Proceed to 
ADJUSTMENT OF VR-1. 

PRO-2104/5/6 ALL: ADJUSTMENT OF VR-1: 

Push the front panel SOUND SQUELCH button ON. Turn the 
SSQ switch OFF and the DSQ switch ON. Attach a voltmeter 
(-) to ground and (+) to Pin 5 of U-1. Tune the scanner 
to a strong, noisy data channel or to a loud, single tone 
carrier. (Cellular or trunked data channels are ideal!) 
Measure the DC voltage at Pin 5 of U-1, (4.5v typical). 
Calculate 80$ of that voltage; then put the voltmeter at 
Pin 4 of U-1 and adjust VR-1 for the 80$ level of the 
above measurement. Typically, about 3.6 to 3.8v. The 
exact adjustment isn’t too critical, but if set too low, 
voice signals will resume SCAN or SEARCH. If set too 
high, then data 4 tone signals won’t trigger the 
SCAN/SEARCH RESUME. Another way to find the optimum 
setting is to put a voltmeter (+) on Pin 2 of U-1 and (-) 
to ground and tune the scanner to a cellular or trunked 
data channel. Adjust VR-1, first one way and then the 
other and then to a point so that the voltage on Pin 2 of 
U-1 just becomes stable with a nice and steady +5 volts. 
It takes a steady 5-volts for about one second to trigger 
the SCAN/SEARCH RESUME function, but don't adjust VR-1 
any further than necessary to stabilize the DATA/TONE 
voltage at Pin 2. 


OPERATION & TECHNICAL NOTES: Remember that the SOUND 
SQUELCH button on the front panel must be ON before 
either SSQ or DSQ can work. The SOUND SQUELCH button is 
kind of like a master on/off switch and the two SPST 
switches control one, the other or both 

Voice signals will cause the scanner to stay locked as 
normal until the signal goes away. Minor adjustment of 
VR-1 may be necessary for optimum results, but the final 
setting will produce a voltage on Pin 4 of U-1 of about 
80$ of the peak voltage on Pin 5 of U-1. The DC input 
signal at Pin 5 of U-1 will be nearly zero on silent or 
quiet signals and about 4 to 4.5v with data & continuous 
tone signals. Pin 5 will show a very erratic and rapidly 
changing voltage from nearly zero to 4 volts or so for 
voice signals. The DC output voltage at Pin 2 of U-1 
will be nearly zero on silent or quiet signals; and a 
steady +5v with data & continuous tone signals. Voice 
signals will cause a rapid fluctuation of the signal 
between 0-5 volts at Pin 2 of U-1. When the SOUND 
SQUELCH button is off, neither SOUND nor DATA SQUELCH are 
operable and scanner operation will be completely normal. 

IN CASE OF DIFFICULTY: The most critical part of this 
mod is the rectifier circuit consisting of D-1, D-2, R-1, 
R-2, C-1 and C-2 and proper pin wiring of the LM-339 
chip. Make sure the diode polarities are correct (banded 
end is the cathode). Make sure polarities of capacitors 
are correct. Tune the scanner to a strong cellular (879 
MHz - 881 MHz) or trunked data channel (851 MHz - 866 
MHz), and measure the DC voltage at Pin 5 of U-1. There 
should be between 4 and 4.5 volts. You won't measure 
"too much" but not enough is possible. If so, check the 
wiring and components mentioned above. Next most 
critical is the polarity and wiring of the two isolation 
diodes, D-3 and D-4. Last but not least is the wiring of 
U-1. The circuit is so simple and affirmative in its 
action that you're not likely to encounter trouble if you 
follow these instructions. 

Some PRO-2005 (not PRO-2004 or 2006) may have a chirping 
or warbling, morse code type of sound on quiet channels 
after this mod has been done. If yours exhibits this 
weird sound, change C-1 from 1.0-uF to 0.1-uF, Radio 
Shack #272-1432. If the "tweet" is still there, then 
solder a 1,000-uF capacitor (RS 272-1032) directly to 
Pins 4 and 11 of IC-5 in the scanner. Pin 4 should get 
the (+) lug of the capacitor while Pin 11 gets the (-). 
This is a peculiar problem in some PRO-2005's, but it's 
easy to correct so don't worry about it. 

If you can't resolve a problem, send me a SASE and one 
loose extra stamp with a complete description of the 
problem and its symptoms and I’ll respond with written 
suggestions and advice. Sorry, no phone calls, please. 

THEORY OF OPERATION OF THE DATA/TONE SQUELCH 

To understand the simple operation of my DATA SQUELCH, it 
is first necessary to understand the PRO-2004/5/6's SOUND 
SQUELCH (SSQ) circuit on which we will "piggy back" the 


"THE WORLD SCANNER REPORT" (c) 1991; V1N10 - Nov-Dec, 1991; Page 7 



new DATA SQUELCH circuit. The circuits are identical 
among the PRO-2004/5/6 scanners but circuit symbols 
differ. Bear with me here while I use a simple scheme 
for this discussion. P4 means PRO-2004; P5/6 means 
PRO-2005 & PRO-2006 and P4/5/6 means ALL. 

SOUND SQUELCH THEORY OF OPERATION: A weak portion of 
the receiver's audio is sampled at the detector and 
amplified through IC-5 ( P4/5/6 ). The highly amplified 
audio is fed from IC5, (P4, Pin 1* or P5/6 . Pin 7) to a 
rectifier network (P4, D-41 & D-42; or P5/6 . D-43 & 
D-44). This rectifier network converts audio signals to 
a DC level proportional to the level of the audio signal, 
and is used as a bias to turn on or off a switching 
transistor, (P4, Q-21; P5/6 . Q-19). Most audio signals 
are strong enough to turn the transistor on while very 
weak or silent signals keep it off. When the transistor 
is off, 5-volts is on its collector, but when the 
transistor is ON, the collector drops to nearly zero 
volts. 5 volts and 0 volts forms the logic required by 
the CPU for making decisions. The collector of the 
transistor is fed directly to the CPU, (P4, IC-503, Pin 
24; or P5/6, IC-501, Pin 18). When the SOUND SQUELCH 
button on the front panel is set to the ON position and 
when CPU’s SSQ pin is at zero volts, the scanner SCANS or 
SEARCHes as normal, locking on any signals which break 
the squelch. Similarly, when the SOUND SQUELCH button is 
off, a ground is placed on the CPU's SSQ pin, which keeps 
it at zero volts, no matter what. 

When the SOUND SQUELCH button is on, and when the scanner 
encounters a silent or unmodulated carrier, then the 
transistor discussed above gets turned off and a 5-volt 
level on its collector is fed to the CPU’s SSQ pin. 
5-volts on the CPU's SSQ pin makes the scanner resume 
scanning within a second or so after stopping. As long 
as there are voices or other audio signals present, the 
CPU's SSQ pin will be ”0-v low” and operation is normal. 
When that pin goes "+5v high", the CPU is programmed to 
resume scanning or searching. 

DATA SQUELCH THEORY OF OPERATION: Since the CPU's SSQ 
pin responds only to low and high logic and really 
doesn't know the difference between voice and data, we 
can generate this logic with a separate but opposite 
logic circuit to make it discriminate against tones and 
data in the same way the SSQ discriminates against silent 
carriers. All we need is a circuit that sends a "high” 
to the CPU's SSQ pin in the presence of strong, sustained 
audio signals such as data or continuous tones. My DSQ 
does this nicely, thank you, since voice signals are 
erratic, varying, and not at all like data or continuous 
tones. C-1 of our circuit samples the same audio as the 
SSQ but passes it to a new rectifier circuit, D-1 and 
D-2, which with R-l, R-2 and C-2, creates a DC signal 
proportional to the level of the audio signal. This DC 
signal is fed to Pin 5 of U-1, a Voltage Comparator 1C. 
A reference voltage is adjusted by VR-1 and fed to Pin 4 
of U-1. As long as the DC signal at Pin 5 is less than 
the reference signal at Pin 4, the output of U-1 at Pin 2 
will be zero volts "low”. When the DC signal at Pin 5 


exceeds the reference voltage at Pin 4, the output of 
U-1, Pin 2, will go high to +5v. 

The output of U-1, Pin 2 is coupled to the CPU via 
isolation diode, D-3. A "high” will tell the CPU to make 
the scanner resume SCANning or SEARCH ing while a "low” 
does nothing unusual. When VR-1 is correctly adjusted, 
the output of U-1, Pin 2 will never go "high" long enough 
to trigger the CPU unless data or continuous tones are 
present. Strong voice signals may make U-1's output go 
high momentarily, but the interval will not be long 
enough to trigger the CPU unless the talker does an 
extended "Ahhhhhhhhhh" into the mike, because about .5 to 
1 sec is required before the CPU will trigger. Most 
voice signals of interest will not send a lengthy "high” 
to the CPU, but continuous tones and data will! There- 
fore, my DATA SQUELCH works just like, though inversely 
to the SOUND SQUELCH. 

Isolation diodes, D-3 and D-4, allow the SOUND SQUELCH 
and the DATA SQUELCH to work simultaneously and not 
interfere with each other. Depending on the setting of 
the individual DSQ & SSQ switches, both data/tone and 
silent signals can cause the scanner to resume SCANning 
or SEARCHing, but voice signals will not be affected by 
either the SOUND or DATA SQUELCH! 

PARTS LIST FOR DSQ CIRCUIT (HOD-44al 
Ckt 

Syro Description 

C-1 1-uF/35vdc Tant; #272-1434; See "Difficulty" text 
C-2 2.2-uF/35vdc Tantalum; #272-1435 

D 1 -4 1N4148 or 1N914 switching diodes; #276-1122 
R-1 390-ohm; #271-018 

R-2 12-k; use 10-k + 2.2k in series if need be. 

R-3 3.3-k; #271-1328 

U-1 LM-339 Comparator; #276-1712 

VR-1 10-k ohm trim pot; #271-282 

XU-1 1C Socket, 14-pin DIP, for U-1 above; #276-1999 

Misc Perf board; #276-1395 

Misc Hookup wire; #278-776 or #278-775 

SI, 2 Switch, SPST Toggle Switch, #275-624 

MERRY CHRISTMAS & HAPPY NEW YEAR 

Kell, that's it; we've run out of space and there's still so much more to 
write. I am saddened to come to the end of an issue and and the end of a 
year and still have items on the list not checked off. In away, it's 
called "job security" since a dead end won’t be reached with the next issue. 

I laugh at myself now to think about my feelings upon completing Vol-I of my 
SCANNER MODIFICATION HANDBOOK . (I wondered if there would ever be anything 
else to write about.) I worried about it again last January as we launched 
the "KR", but by mid-year, the checklist only got longer and longer after 
every issue. One thing grew to inspire another. This spirit is now being 
carried into 1992. Ke've only begun! My excitement is rising to a 
crescendo over the prospects of what yet lies in store for the radio 
monitoring hobby. I hope some of this has rubbed off and renewed or 
invigorated your enjoyment and pleasure. A psychic once told me that my 
mission in Life is to be at the service of others. It's my fondest hope 
that the "fSR" has served your best interests this year, and if it has, my 
commitment is to make 1992 even better. Merry Christmas and Happy New Year 
to all! 73/bc S Staff 


"THE WORLD SCANNER REPORT" (c) 1991; V1N10 - Nov-Dec, 1991; Page 8 



WIRING & COMPONENT PLACEMENT DIAGRAMS FOR DATA/TONE SQUELCH (MOD-44a) 


COMPONENT 

SIDE 



BMS GfiOVtJb 

oj i/te 


PERF BOARD 
ASSEMBLY 

/JOTS: C/tcuiT PAS 

gfcA / F:6Lb PfiO\)Sf/ AA/i> 

Tes7<2l> Fofi A- Ye**' 

/ t ujoaks Pot A ojibe \/ fittery 
OF T/&TA Attp Mot/- \Jotca 

5/&v//t4 s • peofte 5 Ay 

/T "POSS A/oT PSJSC/ Tf/c. 
fc> Of TAB <S*c /(a + 
TfiUAJKep f S/S7B/H’ 

orvetts 6 A/ ir AS t/E*y ^ 

PTFFfcTive OA/ee/b+.g^ 

A/o AttfrorneMT or/ Pf/ . — ~ 
on-Ks/t sysretH (/nAjofi in/ ) j 
fboje/e/t f -bur Yt»J TFu-#t. 
lose. /n'/t/z e/cLusi/t=L.y ‘“'rH , 
SupetS tesucTS toofe'tf- /***• 


SOLDER 

SIDE 

KO-I 

pu/tz. 



lOOAJP 


/S/MS' GfiOofO 
UJ/tiS 


COMPONENT 

SIDE 


SA/ne LAYOUT 
A 5 A/Z0 


PR I NTED 


HOME MADE 
CIRCUIT BOARD 



A/or£i #6 ueev 70 aiakb 
A Pttf/TSD atcuir. 7 7/tf 
"pe/iF doAtfl) UBfi.HO/J /'.S 
Qutcxefi A/Jp JUST A5 
<£troT) . 

AJ&7S: YA/S C/ficu/F /MAS A/qT 

aah> a*// abu/s/o/Js /A m* 

y£A/t 77/AT //"i ZBS/J 7&Aai> - 
27 f you HAUe Oa>£ ACASAt/yj 
/r's t/A/cft/H/Gei) As or 
/O-30-?/. 


SOLDER 

SIDE 





GAOO ut> 
Tt/CB 


_&fiOUfib 

TfifiCG 


"THE WORLD SCANNER REPORT" (c) 1991; V1N10 - Nov-Dec, 1991; Page 9 


CONFIDENTIAL SUBSCRIPTION ORDER: Please print clearly 

V 1 N 1 0 

10/26/91 SUBSCRIPTION RATES 4 ORDER BLANK V1N10 

NAME: 


USA RATES: (Canada + 10% ; Other Foreign +20%-surf or HflVAir) 

*SR BACK ISSUES ONLY USA $$ Check Items 

STREET: 

1991 Single copies; your choice: 1 ea $ 4 . 00 
1991 (1st 6-mos, Jan-Mav/Jun) 5 ea $15.98 

CITY: STATE: ZIP: 

1991 (2nd 6-mos, Jul-Nov/Dec) 5 ea $15.96 

199! (1st Year, Jan-Nov/Dec) 18 ea $25.88 

PHONE :( 1 AMT ENCLOSED: $ 

m CURRENT SUBSCRIPTIONS ONLY 

1322 Single copies; your choice: 1 ea $ 4.00 

THE BELON QUESTIONS ME OPTIONAL BUT HILL HELP US HELP YOU! 

1992 (Jan-May/June) 6-mos 5 ea $15.80 

Radio Interests? (Put YEARS OF EXPERIENCE in each block that applies) 
VHF-UHF Amateur CB Shortwave Professional 
Scanning? Radio? Radio? Listening? Radio? 

1992 (Jan-Nov/Dec) 1-yr 10 ea $25.00 

1992-3 (Jan 92-Nov/Dec 93) 2-yr 20 ea $45.00 
OTHER LITERATURE AVAILABLE 

Career/Profession 
Or OccuDat ion : 

HOBBY RADIO BUYER'S DIRECTORY $14.95 ppd surf 

SCANNER MOD HNDBK. Vol-1: $11.95 > $3.00 S&H * 

List makes & models of your scanners S other radio equipment: 

Describe your technical abilities & interests; use reverse as needed. 

SCANNER MOD HNDBK. Vol-2: $17.95 + $3.00 S&H * 

* Canada USU SBH; Other Foreign US$5 SSH; extra for Air Hail 

MAKE REMITTANCE PAYABLE IN US FUNDS TO: COHHTRONICS ENGINEERING 

Enclose a #10 S’.A.S.E. and one loose extra stamp if you want 
hobby in f o & persona! reply! Business/trade inquiries exempt. 








'/VA/h £ec&)0&£j 


XC-&CAU.)' 

VV /¥ . I 

p(D -2 O0<J 
P/N 7 I 
^ fito-lc6S . 

- ZoC(o | 


SCAMU£P^ 
GAouvV ✓ 


SCHEMATIC DIAGRAM FOR DATA/TONE SQUELCH CIRCUIT (M00~44a 


(j£CLO<n) 


ADJUST 1 fK-l SO 

P/U 4 MEASURES 

A-AA/to* 3<<oV. S6E 

T£XT PCX TM£T 
PPeosE <uAy, VP-1 



XC Scorer 

/s xu-/ 


■4 

u-r 

4.M-339 

■ s s<£ 


(fkve) (otoMel 


sfjK 

AON * AON 


LB6 e//j> 


S LM-339 

r. top w«V 


More B 

?R6-ioo4 : Desolosr sxyfiLve 
Us i fie FAt#\ MA/h Bca/{l> Awl 
Route to S-> i s-z 


PRO -2005/(3 '■ Cut SKyauie cooee 
HAtFojV/ Berweev c*J3,P/n i 
A JJT> THE LDCric/CfiU BiAPD 


PRO-200^: CN-So<4 t Pi*) IS - 
(Sk/ 6 tve co nee) 

p/eo-Z oos/fe '• CU'3 ,P/H 4 

(SKV BLoe um*eJ 


LO&itc/CPU 

ftOMT) 


(SkY Blue) 


CPU 

XC-S03 - PA0-2G6H 

XC- 501 ~ PRO -2005/6 

* P/V 2 V - A/lo-ioof 
P/NI6-PXD-2COS/6 ■* 

(Lode/ CPU 36 API)') 


More ft 


O*/ ^Aia.) 


P-520 OFF 
j/oT USE i) 

IAJ />£0-2O64 


slo Ter ft 


3op*/?i> 


"THE WORLD SCANNER REPORT" (c) 1991; V1N10 - Nov-Dec, 1991; Page 10 


COMMTRON I CS ENGINEERING 
"THE WORLD SCANNER REPORT" 
PO BOX 262478 
SAN DIEGO, CA 92196-2478 


V 1 N 1 0 
911026 


IN THIS ISSUE 


FIRST CLASS HAIL 


+ Easier to understand subscription blank 
t Last Call to Renew for 1992! 

+ HSR Hants to Buy a Real Cheap Computer! 

+ The Latest On Computer Interfaces from 
DataMetrics, RH Systems, and others 
♦ Serial CPU Data Interceptor /Decoder for PRO-2WJ4/5/6 
+ Tone Decoder/Rejector (MetroMod) For All Scanners 
+ Data/Tone Squelch (MOD-44a) for PRO-2004/5/6 


+ SUBSCRIPTION EXPIRES? RENEW SOON l