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THE RADIO SHACK PRO-43 PORTABLE SCANNER
by Bob Parnass, AJ9S
The new Radio Shack PRO-43 is a small portable scanner made
by General Research Electronics (GRE) which lists for about
$350. Although it is a good step above other Radio Shack
portable scanners, hobbyists awaiting a portable version of
the famous PRO-2006 scanner will be somewhat disappointed.1
For instance, the PRO-43 is an "extended coverage" and not a
continuous coverage scanner, covering these bands:
30 - 50 MHz (5 kHz steps), [30 - 88 MHz after modification]
118 - 136.975 MHz (25 kHz steps)
137 - 174 MHz (5 kHz steps)
220 - 225 MHz (5 kHz steps)
225.0125 - 512 MHz (12.5 kHz steps)
806 - 823.9375 MHz (12.5 kHz steps) [806 - 999.9875 MHz
after modification]
851 - 868.9375 MHz (12.5 kHz steps)
896 - 999.9875 MHz (12.5 kHz steps)
Note the omission of the 10 meter ham band, the cellular
phone band, the 75 MHz band, and the lack of coverage above
1000 MHz. Luckily, the September 1992 issue of Monitoring
Times details a modification to restore cellular phone band
coverage and expand VHF-low band coverage to 30 - 88 MHz.2
While the PRO-2006 has 400 channels, the PRO-43 has only 200
channels divided into 10 banks. Individual lockout and 2
second rescan delay may be selected for each of the memory
channels. Users may select between AM and narrow band FM on
any frequency. The PRO-2006 has 10 pairs of search limits
__________
1. See "The Realistic PRO-2006," by Bob Parnass, AJ9S, in
Monitoring Times, October 1990.
2. Speaking from experience, this modification is
conceptually simple, but is quite a bit more difficult
than restoring coverage in other scanners. It requires
skill and good tools, including a tiny soldering iron.
One must desolder a tiny surface mount diode and
resolder it in a different place observing the proper
polarity.
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but the PRO-43 has only one pair and the step sizes are fac-
tory set. The PRO-2006 had selectable step sizes.
Both models have 10 "monitor" memories which can be written
manually during a search.
The HyperscanTM feature means the PRO-43 is supposed to scan
at 25 channels per second and search at 50 steps per second.
The radio scans twice as fast, measured at 50 channels per
second by the reviewer! When enabled, the priority channel
is checked every 2 seconds. As in the PRO-2006, any channel
may be designated as the priority channel.
Physical
The PRO-43 is just the right size for a portable scanner.
It is smaller than the PRO-37 and Uniden 200XLT but larger
than the tiny Icom R1.3 The gray plastic case feels about
the same as a 200XLT, neither as rugged as the Icom IC-2GAT
walkie talkie, nor as thin and chintzy as the PRO-37.
Inside, there are 3 printed circuit boards and most of the
components are of surface mount technology.
The top panel contains volume and squelch knobs, a 1/8" ear-
phone jack, and a BNC antenna connector. A plastic belt
clip of dubious strength is fastened to the rear with 2
screws.
A semirigid rubberized antenna is furnished with the PRO-43.
Performance Issues
The PRO-43 and Uniden 200XLT were tuned to the same frequen-
cies both using their stock rubberized antennas.
On 857.4375 MHz, the PRO-43 heard Joliet Police signals full
quieting which barely broke squelch on the 200XLT, due
partly to the poor 800 MHz performance of the antenna sup-
plied with the 200XLT. When the PRO-43 antenna was placed
on the 200XLT, the 200XLT reception improved noticeably, but
it was still not as good as the PRO-43.
__________
3. See "Uniden/Bearcat 200XLT Scanner Review," by Bob
Parnass, AJ9S, in the RCMA Journal, October 1988.
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On 146.94, 162.475, and 460.1 MHz, the PRO-43 and the 200XLT
were close in sensitivity.
When connected to an outdoor AV-801 antenna, paging
interference rendered several VHF high band channels unus-
able. The problem disappeared when using the rubberized
antenna supplied instead.
Owing to the use of up conversion, a high first intermediate
frequency, images don't appear to be a problem as they were
on other Radio Shack portable scanners like the PRO-34 and
PRO-37. The PRO-43 IF frequencies are specified at 608.005
- 611.2 MHz, 48.5 MHz, and 455 kHz.
Somewhat "Mushy" Audio
The PRO-43 uses an LM-386 audio output IC and the radio is
loud enough, but distorts severely when the volume control
is advanced too far. This is partly due to the internal
speaker as there is less distortion when using an external
Motorola lapel speaker plugged into the earphone jack.
The PRO-43 audio lacks high frequency response. By com-
parison, the Uniden 200XLT has cleaner audio and more of it,
especially when using the internal speaker.
Batteries
The PRO-43 requires 6 AA batteries, but none are included.
A battery clip slides up into the bottom of the radio case
and a separate trap door slides over it. Alkaline cells or
NiCd cells will bring the scanner to life. Like most other
Radio Shack portables, there are 2 jacks on the side, but
they are smaller than usual. An optional, AC operated "wall
wart" power supply/charger can power the radio or recharge
NiCd batteries.
Current drain from batteries was measured at 88 ma. while
scanning and 90 - 140 at various settings of the volume con-
trol with the squelch open. The PRO-43 averages 36% higher
current drain than the 200XLT which means the batteries will
need recharging more frequently.
Keyboard and Display
The user manual explains that the KEYLOCK slide switch "dis-
ables the keypad to prevent accidental program changes." In
truth, most of the keys are disabled. The MANUAL and SCAN
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keys remain enabled.
The liquid crystal display (LCD) is a smaller version of the
display on the PRO-37. Being smaller, it is somewhat more
difficult to read than the 200XLT display. Pushing the
LIGHT button lights a single lamp behind the display. It
stays lit for only as long as you keep the button pressed
and is not latched or timed as in the 200XLT.
Summary
People who want a portable which covers both civilian and
military aircraft frequencies should check out the PRO-43.
The PRO-43 will be attractive to hobbyists who want more
frequency coverage and fewer images in a smaller package
than the PRO-37 or Uniden 200XLT and who don't want to fight
the problems of using the more feature rich AOR 1000XLT.
x
IMPROVED AUDIO FOR THE PRO-43 SCANNER
by Bob Parnass, AJ9S
The Radio Shack PRO-43 scanner audio is too bassy.1 The
lack of treble makes it difficult to hear the PRO-43 in
noisy situations, especially while listening in a car
or truck. Louis Shirley sent me a schematic and sug-
gested I remove C341, a tiny 0.015 ufd surface mount
capacitor.
I'm glad to report that removing C341 made a great
improvement. The audio is now much "crisper," more
like the Uniden 200xlt, although still not quite as
loud. Turning the volume control up still overloads
the PRO-43's small, internal speaker, but there's less
need to do that once C341 is removed.
The PRO-43 contains 3 printed circuit boards, and the
middle (second) board contains the audio circuitry.
Finding C341 is difficult, as it is neither marked with
a value nor a component designation. It is located on
the foil side of the middle board, under IC304, an
LM386 amplifier IC. C341 is in parallel with, and phy-
sically next to, R350 (33,000 ohm). R350 is slightly
larger than C341 and is marked 333. Both R350 and C341
are connected between pin 2 of the LM386 and ground.
A Note About 50-88 MHz Reception
Now that I have a schematic, I see that the European
version of the PRO-43 has different coils and capaci-
tors in the low (mid) band front end filter. That
explains why the 75 MHz sensitivity isn't stellar after
adding diode D3 to enable 30-88 MHz coverage.
__________
1. See "PRO-43 Product Review," by Bob Parnass, AJ9S, in
the November 1992 RCMA Journal.
===============================================================================
Bob Parnass, AJ9S parnass@ih4gp.att.com
Distinguished Member of the Technical Staff (708)979-5414
AT&T Bell Laboratories Knife collector, woodworker
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