

Article 11898 of rec.ham-radio:
Path: philabs!prls!pyramid!decwrl!sun-barr!rutgers!att!ihuxz!parnass
>From: [email-masked] (Bob Parnass, AJ9S)
Newsgroups: rec.ham-radio
Subject: Re: Uniden Bc-760XLT
Summary: 760XLT review - the good, the bad, and the ugly
Message-ID: <[email-masked]>
Date: 17 May 89 01:23:12 GMT
References: <[email-masked]>
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