parnass@ihu1h.UUCP (Bob Parnass, AJ9S) (01/07/86)
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Owner's Report: Uniden/Bearcat 800XLT Scanner
Bob Parnass, AJ9S
Manufactured in Taiwan, the 800XLT is the first programmable
Uniden/Bearcat scanner to cover a portion of the 800 MHz
band. Covering 40 channels in 2 banks the 800XLT is speci-
fied to receive in the following ranges:
TTTTAAAABBBBLLLLEEEE 1111.... 800XLT Frequency Coverage
________________________
| 29 - 54 fm|
| 118 - 135.975 am|
| 136 - 174 fm|
| 406 - 512 fm|
| 806 - 912 fm|
|________________________|
Only a portion of the new 902-928 MHz ham band is covered.
Differs From Past Models
There are several differences between this scanner and its
Bearcat predecessors.
- There is only a single scan/search speed: fast!
- 800XLT channel banks contain 20 channels, not 10 as in
previous models. Although we should be thankful for
the inclusion of a channel bank feature, doubling the
number of channels in a bank is a step backwards.
- Scan delay, channel lockout, and priority enable are
indicated by separate, colored LEDs rather than the
numeric display, making a colorful light show.
- Both the selectable scan delay and the priority sam-
pling period are 3 seconds vs. 2 seconds in the older
scanners. Although a matter of personal preference, I
like the 3 second scan delay, but would opt for a 1 or
2 second priority sampling period.
- Despite claims on the 800XLT box to the contrary, a 2
digit channel counter is displayed while scanning, as
in the BC350, rather than "rolling zeroes" of the
BC210/220/250/300. This is unfortunate, as rolling
zeroes make it easier to discern what channels are
locked out from scanning without having to step through
each one manually.
- The keyboard has a good feel, although quite different
from the "chicklet" keyboards on Bearcat 250 and 300
scanners. Keys travel further, with less of a positive
click. The 800XLT keyboard is much easier to read, as
each key has its function printed right on the keytop,
rather than labeled above it on an inlay.
- The 800XLT seems to lack "window detection" circuitry,
so the scanner may stop prematurely (off frequency) in
the SEARCH mode.
- There is no date of manufacture stamped on the cabinet.
- Mobile DC power cord is optional, but is supplied as
standard equipment with other Bearcat scanners.
Inside Appearance Pleasing
The inside of the 800XLT consists of 3 circuit boards:
1. a main receiver board, containing vhf/uhf front ends,
IF stages, audio amplifier,
2. a feature board, containing microprocessor and key-
board logic, and
3. an 800 MHz front end board, which uses surface mount
components.
The boards appear very neat, and it is obvious that computer
aided design and automated component insertion techniques
were used. What a welcome change from the chaos inside a
hand assembled BC250!
No schematic diagram is furnished. Whereas the identity of
many of the ICs in earlier Bearcat scanners was obscured by
the use of "house numbers", the ICs in my 800XLT are clearly
marked with their original designations (e.g. National
LM382). This makes repair easier, as one may obtain parts
from several sources rather than being forced to buy from
Uniden.
Side-by-Side Performance Comparison
Side-by-side tests were performed, switching a Butternut
SC3000 tri-band antenna at 20 feet among 3 scanners: the
800XLT, a new Bearcat 260, and an old Bearcat 300 workhorse.
The test equipment used was a pair of human ears, which we
all use when scanning.
As the following table shows, the 800XLT was more sensitive
on some frequencies, but suffered much more overload from
strong signals. This is important if the 800XLT will be
used with an outdoor antenna. The 800XLT had fewer annoying
birdies than the other models tested.
TTTTAAAABBBBLLLLEEEE 2222.... Performance of Bearcat 800XLT vs. 260 vs. 300
_____________________________________________________________
| Band || Bearcat 800XLT | Bearcat 260 | Bearcat 300 |
|___________||__________________|________________|________________|
| 30-37 MHz|| more | more | less |
| || sensitive | sensitive | sensitive |
| || | | |
| || weak | moderate | moderate |
| || birdies | birdies | birdies |
| || | | |
| || overloaded by | no overload | no overload |
| || paging, police | detected | detected |
| || mobile phones | | |
|___________||__________________|________________|________________|
| 37-50 MHz|| equally | equally | equally |
| || sensitive | sensitive | sensitive |
| || | | |
| || overloaded by | no overload | no overload |
| || paging, police | detected | detected |
| || mobile phones | | |
|___________||__________________|________________|________________|
| vhf || more | N/A | less |
| aircraft || sensitive | | sensitive |
|___________||__________________|________________|________________|
| vhf-hi || slightly more | slightly more| slightly less|
| || sensitive | sensitive | sensitive |
| || | | |
| || overloaded | no overload | no overload |
| || by paging | detected | detected |
| || | | |
| || heard 162.55 wx| | |
| || on 147.19 | | |
| || and elsewhere | | |
|___________||__________________|________________|________________|
| uhf || more | less | less |
| || sensitive | sensitive | sensitive |
| || | | |
| || overloaded | no overload | no overload |
| || by paging | detected | detected |
|___________||__________________|________________|________________|
On the 800 MHz band, several police, business and cellular
telephone stations were received using the supplied 3"
antenna. Clear reception of a repeater used to dispatch
Chicago Tribune photographers was possible from 50 miles
distant.
The 800XLT audio output is clean and strong, with little
synthesizer whine.
Early Problem Fixed: Memory Loss
My 800XLT lost its memory contents when unplugged from
117VAC, even though loaded with a fresh pair of alkaline AA
batteries. The problem was traced to a metal contact,
installed backwards in the battery holder. Repair required
desoldering a red wire, repositioning the contact, then
resoldering the wire. No further memory problems have been
encountered.
Too Much Hysteresis in Squelch
There is too much "free play" in the stock 800XLT squelch
control, the same affliction designed into Radio Shack
scanners. The remedy consists of replacing the 860K ohm
resistor on pin 14 of the MC3359P IC with a 2.2M ohm resis-
tor.
Not As Selective as Older Bearcats
At -55 dB @ +- 25 KHz, the 800XLT IF selectivity is not as
good as the BC350 and BC300, which are rated at -60 dB @ +-
25 KHz. The wider selectivity causes the scanner to stop
prematurely in the SEARCH mode, and makes it difficult to
determine, for example, if a station is transmitting on
855.2500 as opposed to 855.0125 MHz.
Since the 800XLT tunes in 12.5 KHz steps on the 800 MHz
band, the wider selectivity is handy when scanning telephone
cell sites, which are on channels spaced on 30 KHz apart.
Overall Evaluation
The 800XLT is the most conventional and easiest to operate
of the new 800 MHz-capable scanners. It is plagued neither
with the slow scan/search rate of the Regency MX7000, the
low audio output of the MX4000, nor the unfriendliness of
the Yaesu scanning algorithms.
The 800XLT's tendency to overload on strong signals and awk-
ward squelch action detract from an otherwise good perfor-
mance.
--
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Bob Parnass, Bell Telephone Laboratories - ihnp4!ihu1h!parnass - (312)979-5414