"an_old_friend" wrote in message
oups.com...

Frank Gilliland wrote:
On Thu, 01 Sep 2005 00:12:57 GMT, "Jim Hampton"
wrote in :


"Frank Gilliland" wrote in message
.. .
On 31 Aug 2005 11:11:52 -0700, "Bob" wrote in
.com:

Saw this morning a brief mention on Fox News about hams doing health
and welfare emergency traffic for New Orleans. "Only reliable
communications in the area". They showed a few ham transcievers, one
displaying a 70cm band frequency, another HF rig on 20 meters in the
phone subband.

This is the sort of disaster that ham radio handles well. Cell phones
are mostly out, as well as most any other comm system that needs
physical infrastructure to function.


I guess that means CB radios aren't working either, huh?




If a large area is devestated, one just might need a couple hundred mile
range 24/7. Even battery powered HTs through a repeater can get you 30
to
100 miles total between users. Hf rigs can supply you continuous
coverage
24/7 from local to thousands of miles. You just select an appropriate
frequency (ranges of a few decades in frequency may be involved here).

There may be a lot more cbs, but if you can only get 10 or 20 miles and
you
keep receiving skip from other stations far away running power ....


I never knew there was a minimum range for emergency communications.
So how far does a radio wave have to go in order to get this
distinction? A couple hundred miles? More than 10 or 20 miles? Is
there some FCC rule that defines this distance?

150 miles is the max legal CB range (a very stupid rule BTW) but in an
emergency anything goes that works

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In disasters, the real problem is not the rules but the nature of radio wave
propagation on the 11 meter band (as well as the similar 10m and 12m ham
bands). You can get close in (10 to 20 miles) via line of site or you get
skip out to thousands of miles via ionospheric propagation when the solar
flux is high enough. However the intermediate distances of a few hundred
miles just are not going to be covered unless you are lucky enough to get
some uncommon propagation modes like backscatter.

Dee D. Flint, N8UZE