- 1 - 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 - 2 - 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. - 3 - 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. - 4 - 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. - 5 - 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. - 6 - 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. - 7 - 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. - 8 - 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. - 9 - 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 - 10 - 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... :-)