On Tue, 20 Nov 2007 19:39:12 -0500, 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? 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.

Increased sensitivity/filtering? Hype?

With the "right" kind of propagation even .5W will do way over 100 miles but under normal
circumstances count on line-of-sight but no more than 1 mile when in build-up or bushy
areas. Your mileage may vary.

Repeater distances are usually line of sight (a repeater at 4.000 ft has a horizon of abt
80 miles if no obstructions in between. Draw an 80 mile circle around the repeater and
you'll get the area you can reach.

Note: There usually are obstructions (hilly terrain) and without any special propagation
signal strength at long distance will be less. Most FM type radio's do not have very
sensitive receiving stages and if squelch is on sensitivity becomes even less. Solution:
Use narrow band modulation such as SSB. Instead of spraeding your .5W over 15kHz put it
in 3kHz. You'll be stronger on the other end - however now we're talking how it works for
ham-radio: Do a lot with little power.....