In article ,
Steve Calvin wrote:
Sorry if this isn't the right group to ask this, if not and
someone know of a more appropriate group I'd appreciate a
pointer.
I currently have GMRS radios that are rated at "16 miles"
(yeah, maybe on the salt flats or over water, ok, we all
know about that). The are rated at 2W on the GMRS freq's
and .5w on FRS.
Why are the new "25 mile" units still rated at 2W?
The most probable reason is that this is pure marketing hyperbole.
The radios aren't better... they're just being quoted using more
optimistic (and typically unrealistic) test conditions, so that they
sound better than the old radios, so that they'll sell better.
What's
the difference in the two radios to justify the increased
distance claims?
Can't be frequency or a change to the privacy codes or they
wouldn't work with older radios.
They *might* have more sensitive receivers, perhaps with a low-noise
front-end preamplifier.
I rather doubt it, though.
Increased sensitivity/filtering? Hype?
Probably hype.
I've read some reports that indicate (based on buyers' experiences)
that there can be some very real different in useful range between
FMS/GMRS radios of different types. This might be due to actual (vs.
quoted) transmitter power, or to better receiver sensitivity, or to
the use of less-lossy rubber-duck antennas, or to the presence of a
more effective counterpoise within the radio.
I doubt, though, that all of these quality improvements, lumped
together, would come anywhere near extending the range of a 2-watt
handheld from 2 miles to 25 miles, under the same usage conditions. A
12:1 distance improvement would seem to require a 144:1 power or
sensitivity improvement... over 20 dB.
25 miles, on 2 watts of UHF, pretty much requires that both
transceivers be up on hilltops or high buildings, with a fairly clear
line-of-sight between. You aren't going to get that sort of distance
from ground-level to ground-level, unless you're lucky enough to catch
a very fortunate reflection from something high up... the horizon will
cut off line-of-sight. Similarly, you won't get that sort of range
amidst city building clutter.
--
Dave Platt AE6EO
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