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June 24, 2001
GMRS Equipment
Reviews
by Gregory J.
Forrest
Read
the Reviews
The following equipment reviews are
tailored to those who desire a single radio for use in both the GMRS and the
amateur radio services. I review specific commercial/public-safety grade radio
products only. There are several reasons for this:
- Amateur radio transmitters do not meet
the frequency tolerance and transmitter emission standards that are required to
operate above 450 MHz;
- Amateur products provide simple
user-programmability, something commercial product must not be (easily) capable
of;
- Commercial products are designed (and
type-accepted) for use above 450 MHz and can also legally be used on amateur
frequencies (equipment must only meet standards of "good engineering
practice").
How well does a 450-470 MHz radio work
on 440-450 MHz? Performance varies. The most common problem is reduced receiver
sensitivity, or the inability of the VCO (voltage-controlled-oscillator) to
lock and stabilize below 450 MHz. In some cases, the radio will simply not make
the trip down to 440 MHz for one reason or another, or will be limited to a 20
MHz bandwidth (thus 440 to 460 MHz).
Re-tuning the receiver filters and/or
the VCO easily solves the first two problems. It is beyond the scope of these
reviews to describe how to perform these modifications. The last problem cannot
be solved without severe performance degradation to channels at either end of
the 450 MHz band (462 MHz or 440 MHz).
But there is hope. The following
equipment reviews will identify specific commercial models that either (1) do
not need modification for amateur use, or (2) require some mods, but are
otherwise capable.
Benefits of Commercial
Radios
Commercial radios offer features not
found on amateur products. Although commercial radios generally offer fewer
features, the ones they do offer are far more useful.
You may not realize the value of these
features if your only experience has been an amateur radio product. These
features differentiate professional radios from amateur-class products. All
radios in the following reviews provide the following basic features unless
noted:
- CTCSS-capable scanning (scan will not
stop on a signal that has the incorrect CTCSS code)
- Excellent intermodulation rejection
(unlike cheesy scanners and most amateur-class products);
- High speaker volume levels;
- Scan rates (chan./sec.) 200% to 800%
faster than amateur products;
- "Selected Channel" Priority
Scan (where the channel selected through the channel select knob becomes the P1
channel);
- Transmit capability while in scan mode
(scan stops/starts when radios is keyed, unkeyed);
- Minimal priority look-back muting
duration;
- One-touch simplex button (i.e.,
talk-around) feature (not a worthless "reverse" switch!);
- Larger, single-function buttons that
you don't have to look at while driving;
- A CORRECT balance of features and
feature performance;
- Capability of different TX & RX
squelch codes on memory channels; and
- PC or front-panel programming.
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