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UNIDEN/BEARCAT 760XLT SCANNER:
FIRST IMPRESSIONS
by Bob Parnass, AJ9S
Reviews of the new Uniden/Bearcat 760XLT (950XLT) scanner
have been published in Monitoring Times and the All Ohio
Scanner Club's American Scannergram. I've been using my
760XLT for several days now, and here are my observa-
tions.
The 760XLT, also sold as the 950XLT, is a full featured
base/mobile scanner, which makes use of surface mount
technology to cram 100 channels into a small, metal
cabinet. Generous coverage is given to the traditional
scanner bands, including aircraft, 10 meter FM, 6 meters,
and the 800 MHz ranges. A 10.85 MHz first intermediate
frequency (IF) is used, versus the 10.8 MHz IF in the
older Bearcat 300.
Although Uniden sales literature claims the cellular
telephone bands are excluded, my 760XLT came equipped
with this coverage. Some scanner dealers, like Grove
Enterprises, charge about $10 for the scanners they
upgrade with a simple modification to restore cellular
phone coverage. Grove no longer offers the cellular res-
toration modification. I didn't buy the $35 wideband
preamplifier or $69 CTCSS decoder options.
When using the 760XLT with an outside antenna, I experi-
enced intermodulation distortion from paging
transmitters, as was true with the 40 channel 800XLT. In
both cases, the front end circuitry is probably being
overloaded (driven into the non-linear region) by the
strong paging signals.
All is not lost, however. I bought this radio to monitor
local signals, and no intermodulation products were heard
when using the 760XLT connected to an indoor antenna. In
this respect, the 760XLT fares better than the 800XLT,
which sometimes experiences paging interference using
only its internal whip antenna.
The 760XLT does receive images 21.7 MHz (twice the IF)
below the programmed frequency. One can hear pilots,
actually transmitting in the 118-132 MHz range, while
scanning the 140-174 MHz band. Images are nothing new.
Experience shows that scanners employing up conversion,
with high IFs, are less likely to suffer image problems.
Spend the extra money and buy a Radio Shack PRO-2004 or
ICOM R7000 if you want to search the 160-170 range
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without image interference.
I have a difficult time monitoring Naperville Police on
470.3125 MHz using my 760XLT on an indoor antenna. No,
it's not a sensitivity problem, the problem is that the
760XLT hears TV channel 35 audio (601.75 MHz) on 470.300
MHz, and the wider IF filter allows the religious TV
broadcasting signals to interfere with adjacent channels.
My calculations confirm that the 760XLT can hear 601.75
MHz TV on 470.3 MHz due to the phenomenon of multiple
injection frequencies.1 When the scanner is programmed to
470.3 MHz, its synthesizer is generating a signal on
153.15 MHz. The third harmonic of 153.15 MHz is mixed
with the incoming signal to produce an IF of 10.85 MHz.
The TV problem arises because the 4th harmonic of 153.15
MHz is also present, and it mixes with the 601.75 MHz TV
signal to produce 10.85 MHz.2
Sensitivity on 800 MHz and other bands appears adequate.
I can still hear Joliet Police, DuPage County Sheriff,
and Naperville Fire on 800 MHz using a 19 inch whip
antenna in rural Oswego.
The 760XLT and 800XLT squelch controls are sloppy, having
too much hysteresis. I can usually fix this by changing
a single resistor, but the surface mount construction,
and lack of a schematic make modification more difficult
in the 760XLT.
Now for a scanner history lesson. Electra's Bearcat 300
scanner was introduced in the 1979-80 timeframe, and
became a favorite of scanner enthusiasts. The 300
included a new "Service Search" feature, whereby several
FCC allocated frequencies were preprogrammed by the fac-
tory. Users could press one of 11 keys (for Police,
__________
1. See "512-657 MHz Reception on Your Scanner," by Bob
Parnass, AJ9S, in Monitoring Times, February 1985, pg
19.
2. The multiple injection frequency problem plagues other
scanners, like the Radio Shack PRO-30, which can hear
800 MHz signals in the 390 MHz range, and Bearcat 20/20,
which can hear 162.55 MHz weather broadcasts in the
30-50 MHz range.
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Fire, Hams, Mobile Telephone, Aircraft, Marine, etc.)
and the scanner would scan all the preprogrammed frequen-
cies for the specified service.3 This was especially
handy when the scanner went along on vacation, making it
easier to find the local channels for police and fire.
Bearcat's main competitor, Regency Electronics, offered
their version of a Service Search feature in the K500,
M400, and D810 models.
Although the Bearcat 300 has been discontinued, the new
760XLT carries forward the Service Search tradition. The
760XLT Service Search covers only Police, Fire/Emergency,
Aircraft, Marine, and Weather. Service Search banks for
Ham, Industrial, Local Government, Forestry, Transporta-
tion, and Telephone have been dropped, although any these
frequencies can be programmed in the usual manner. A new
feature is "buried" in 760XLT owners' manual, and is not
mentioned in the advertisements. The 760XLT provides the
ability to lock out preprogrammed frequencies, one by
one, from the Police and Fire/Emergency services.
Say you don't want to listen to the hospital paging on
152.0075 MHz (rounded to 152.010), now you can lock it
out of the Fire/Emergency search. Locked out channels in
a given bank can be re-enabled en-masse by depressing the
LOCKOUT key down for 2.5 seconds.
I was looking for a scanner operable in the dark, and the
760XLT fit the bill. The orange LCD display is backlit
at all times, as are the hard plastic SCAN, MANUAL,
PRIORITY, and HOLD keys. The four keys must be lit by
incandescent bulbs, as they get warm to the touch. Since
the solid rubber frequency keys are not lit, one can
operate, but not program the 760XLT in the dark.
When Uniden acquired the Bearcat line of scanners from
Electra, they greatly improved the internal construction,
but started using wider IF filters. The Uniden scanners
are less selective than their predecessors, which means
they are more prone to adjacent channel interference. I
would have gladly paid the extra $3 or so for a better
filter.
__________
3. The recently enacted Electronic Communication Privacy
Act (ECPA) makes it illegal to monitor mobile telephone
calls.
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So far, I like the 760XLT. I paid about $290 for the
760XLT from Grove Enterprises, Brasstown, NC - good folks
who use what they sell.
MORE COMMENTS ON THE 760XLT
by David Woo4
I purchased the Uniden 760XLT [scanner] recently based on
your review.5
I got it sans CMT (cellular mobile telephone) coverage.
It was very difficult to implement the Monitoring Times
conversion for cellular phone. I had to take both covers
off to get pin 20 out of the board. I was unable to cut
the pin from the bottom side with any available tool, so
I ended up unsoldering the pin and yanking it up from the
board from the bottom side.
Once I soldered pin 19 to 20, CMT coverage did function
as advertised.
The 760XLT definitely has a good deal more spurs than the
PRO-2004. Also, the lack of the sound squelch means you
can't scan through IMTS mobile telephones, which place a
carrier on unused channels.
Your comments on the mushy squelch are VERY true. If you
come up with a modification like for the PRO-2004
squelch, scannerdom will certainly appreciate it.
It is possible to use the frequency up and down keys of
the PRO-2004 at night. If you look at the back of the
keypad, there is a shield with a hole in the middle of
it. Last year, Radio ShackO sold a 12V bulb (60 mA?)
with pigtail leads. Unfortunately, they no longer have
it. I put this bulb in a grommet and glued it in the
hole. I grounded one lead and connected the hot lead to
__________
4. David Woo, room IH 4G-319, AT&T Bell Laboratories,
Naperville, IL
5. See "Uniden/Bearcat 760XLT Scanner: First Impressions,"
by Bob Parnass, AJ9S, in The Radio Enthusiast, June,
1988.
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the switch on back of the volume control. Enough light
comes through the yellow keys so that the up/down fre-
quency keys can be found in the dark.
I didn't do the 400 channel conversion, so I don't know
if enough light would come through the commercially
available keypad overlay that was sold in Monitoring
Times.
AVOID TROUBLE WITH THE
760XLT ANTENNA CONNECTOR
by Bob Parnass, AJ9S
The Uniden/Bearcat 760XLT rear panel is outfitted with a
Motorola-type auto radio jack. Around the outside of the
jack is a plastic lip. This arrangement works well with
the supplied telescoping antenna, but can cause trouble
if the scanner is used with an SO-239 adaptor, like the
Radio ShackO #278-208.
The 760XLT's plastic lip prevents one from inserting the
adaptor far enough for the center pin to make reliable
contact. This will result in a serious loss of sensi-
tivity.
The solution is simple. Using a flat file, carefully
file the plastic lip down uniformly by about 1/16 - 1/8
inch. Don't spill the filings into the radio.
Now the adaptor can be inserted farther into the antenna
jack.
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PROBLEMS WITH UNIDEN REPAIR SERVICE
by Bob Parnass, AJ9S
As I wrote in a previous article, I usually fix my own
scanners. However, when a new radio fails, it's incum-
bent on the manufacturer to make good on the warranty.6
My experience with Uniden's Customer Service department
may represent how they treat other customers. If so,
then Uniden's purchase of Regency and Bearcat scanners is
a setback for consumers.
o June 12: I bought a brand new Uniden 760XLT scanner.
On getting the scanner home, it was clear this radio
had memory problems.
o June 14: After speaking with Chris at Uniden Custo-
mer Service, I sent my new scanner to Uniden to fix
under warranty, and was quoted a 15-20 day tur-
naround time.
o August 29: Over two months and several telephone
calls later, I received a replacement scanner that
was also defective.
o September 1: Spoke with Judy at Uniden who asked me
to send back the scanner and promised to ship me a
new one immediately on receiving mine. I sent the
radio back the next day.
o September 16: Receive confirmation from Uniden that
they got my scanner, but they won't ship another one
until October 6!
If answering customer phone calls is any measure of ser-
vice, then Uniden has a long way to go. When the Custo-
mer Service telephone is not busy, I have counted up to
18 - 26 rings before it's answered or I give up.
To be fair, the representatives were usually courteous.
But they were quick to promise, and I learned not to
believe what they said. Nobody there seemed willing to
"own the problem."
__________
6. See "Confessions of a Scanner Collector," by Bob
Parnass, in Monitoring Times, August 1988.
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Twice, in vain, I asked to speak to a supervisor.
Representatives Chris and Judy took my name and phone
number, but my calls were never returned. Neither would
representatives refer me to anyone outside the Customer
Service department.
This poor treatment makes me hesitate to recommend Uniden
service when scanner owners seek my advice.
To make smaller scanners, manufacturers are now using
tiny surface mount components in their new generation
models, including Uniden's 600/760XLT and 100/200XLT
series. This makes it near impossible for even good
repair shops to fix them.
The bad news for scanner owners is that they now have
fewer options for repair service. The bad news for
Uniden is that Radio ShackO and AOR also sell scanners.
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760XLT 800 MHZ AND CTCSS MODIFICATIONS
Peter pas@jupiter.ic.cmc.ca
Canadian Microelectronics Corporation
Hi. A note to BC760XLT scanner owners. I recently agreed
to modify one for a friend a found the following two
notes of interest.
1. It was shipped with a how-to on the cellular res-
toration mod that appears more comprehensive than
those I've seen posted on rec.radio.shortwave or in
Bill Cheek's scanner modification handbooks. Here
it is.
WARNING: If you don't know enough about electronics
and about what you are about to do, you might toast
your radio and if you toast your radio, you only
have yourself to blame; you can't blame me or any-
one else! Also, the moment you twist a screw to
remove a cover, your warranty is gone! Also, moni-
toring of certain services in certain freqency
ranges is prohibited in certain areas.
WARNING #2: Read the warning above again.
a. The following applies to models manufactured
during 1989 (HI code date suffix) or later.
b. Place radio so the front is facing you;
remove top cover
c. You are looking at the FOIL side (other than
surface mount components and a large upside-
down Sanyo IC) of the PCB. Locate this Sanyo
IC. A long row of solder pads just above the
Sanyo IC identifies pins 1-32 of the
microprocessor. Pin 1 is on the left and pin
32 is on the right.
d. Using a sharp-pointed tool, cut the two
traces leading to pin 26 of the microproces-
sor IC. There is a trace coming from above
pin 26 and a trace coming from below pin 26.
e. Solder-bridge pins 19 and 20 together of the
microprocessor IC.
f. Solder-bridge pins 26 and 27 together of the
microprocessor IC.
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g. This part is tricky to identify without a
diagram. Directly above pin 27 is a three
terminal, surface-mounted transistor device.
The lower terminal of this device used to be
connected to pin 26 of the microprocessor IC
until you did step d) above. Solder-bridge
together the two left-hand side terminals of
this device.
h. This part is also tricky to identify without
a diagram. Locate the trace that travels
from pin 19 of the microprocessor IC to pin
26 of the microprocessor IC. Near pin 26,
this trace will have been cut as per step d)
above. Along the length of this trace, there
are two devices that are physically mounted
over it. Of these two devices, the two-
terminal device on the left-hand side is a
4.7k chip resistor marked "472" on it. It is
mounted over the trace in an area approxi-
mately below pin 20 of the microprocessor IC.
Carefully remove this chip resistor and tape
it to the inside of the scanner cover, just
in case...
i. Put the radio back together and try to enter
845. If 845.000 appears on the LCD, you've
done the mod successfully.
2. A $60 option for the BC760XLT is a CTCSS tone
decoder board that plugs directly into the scanner
board. Catalogues indicate you must purchase a
$10-$15 switch assembly in order to enable/disable
the CTCSS option. You do not need to buy this
switch if you are comfortable enabling the CTCSS as
follows:
WARNING: Read the first and second warnings above.
a. Following installation of the CTCSS card on
the component side of the circuit board, you
will have used two row-pin connectors (one
that the CTCSS board plugs directly into and
one for a ribbon cable leading from the CTCSS
card). This leaves a third, five pin, row
connector unused in the general area of the
CTCSS card. This is where the "required"
switch is supposed to plug in.
b. Locate this 5-pin connector on the FOIL side
of the PCB and mentally number the pins 1 to
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5, from left to right (with the radio front
facing you). The CTCSS option is enabled by
connecting pin 5 to pin 2. I did this by run-
ning a wire from pin 5 to the top of the
surface-mounted component directly above pin
5 (which is connected to a large foil area
which is connected to the (mentally numbered)
pin 2). Use your fine soldering skills to do
this however you like.
c. On power-up, the string "CTCSS" will appear
on the bottom right of the LCD display. The
instruction guide tells you how to punch in
PL tones to use the CTCSS option.
I did the above two mods and have found the radio to be
working flawlessly. Your mileage may vary. Now I have to
return the radio to my friend... but without some further
"testing" of course... :-)
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