From philabs!prls!pyramid!decwrl!sun-barr!rutgers!att!ihuxz!parnass Thu May 18 09:27:51 EDT 1989 Article 11898 of rec.ham-radio: Path: philabs!prls!pyramid!decwrl!sun-barr!rutgers!att!ihuxz!parnass >From: parnass@ihuxz.ATT.COM (Bob Parnass, AJ9S) Newsgroups: rec.ham-radio Subject: Re: Uniden Bc-760XLT Summary: 760XLT review - the good, the bad, and the ugly Message-ID: <4505@ihuxz.ATT.COM> Date: 17 May 89 01:23:12 GMT References: <1498@atari.UUCP> Distribution: na Organization: AT&T Bell Laboratories - Naperville, Illinois Lines: 172 x Reviews of the Uniden/Bearcat 760XLT (950XLT) scanner have been published in Monitoring Times and the All Ohio Scanner Club's American Scannergram. I have two 760XLTs, and bought my first one over a year ago. 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-2005 or even ICOM R7000 if you want to search the 160-170 range 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 more than ade- quate. 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, 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. Too bad that none of the service searches ever contains fre- quencies above 470 MHz, a region now heavily used in many metropolitan areas. A new feature is "buried" in 760XLT owners' manual, and is not mentioned in the advertisements. The 760XLT pro- vides 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. 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. If your 760XLT doesn't succumb to "infant mortality," chances are it will provide a few years of scanning fun. I listen to my 760XLTs every day. The trick to the 760XLT is getting one that works right out of the box. One of mine was DOA, and I just got a letter from a two- way tech whose new 760XLT went up in smoke when he inserted the AA backup batteries. If this will be your only scanner, and you can afford the extra $100, I recommend buying the Radio Shack PRO-2005 as it's much more radio. It lists for about $420. Visit your local Radio Shack and check it out. Then, check stock at Grove Enterprises, now advertising the PRO-2005 for about $390. There you have it -- the good, bad, and the ugly. __________ 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. The Electronic Communication Privacy Act (ECPA) now makes it illegal to monitor mobile telephone calls. -- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Bob Parnass AJ9S, AT&T Bell Laboratories - att!ihuxz!parnass - (312)979-5414