On Thu, 2007-07-12 at 19:49 -0500, Kim Elmore wrote:
> I'm looking for some comms advice and I know some of you have a fair
> bit of experience in this area.
>
> I'll be part of a meteorological field project next year (I'm a
> research meteorologist, not a comms engineer). The project will study
> severe weather and will occur within about a 50 x 50 mi area that
> will be decided upon each operational day. Many observing sites will
> be mobile and moving around within the box, but the box itself is
> unlikely to move much once set. The issue is comms (mainly voice or
> low-bandwidth data) between the control center and outlying field
> personnel, and then between the various field locations: how can we
> maintain reliable comms and do it cheaply?
cell phones if they have good rural coverage.
>
> I considered a NVIS system, but I suspect that lightning noise would
> play havoc with that, even if we could obtain enough bandwidth for
> NBFM. Even though we'll be in the southern plains, terrain may be an
> issue in places like the Texas caprock. Outside of satellite comms or
> some kind of balloon-borne repeater, I'm stumped. I'm open to enlightenment!
Perhaps UHF FM with numerous mobile repeaters. You would have a lot
better chance on the range running VHF or UHF SSB, but it will take
really good noise blankers to handle the thunderstorm static. And well
designed SSB receiving filters that don't ring from those static pulses.
Radio communications near a 70,000 foot thunder head that has spun off
an F5 tornado is very difficult. FM rigs may not notice the noise but
they won't HEAR the usual signals either. Back in 1976 when such a storm
passed near here, once I had secured from the wind damage and went to
the next town, we spent a couple hours using the land line to relay for
the sheriff's mobiles who couldn't hear the courthouse less than 15
miles away because of the noise from that thunderhead even though it
probably had moved 40 or 50 miles. Fortunately the ham in town had a CD
radio on the sheriff's low band frequency and we were able to talk to
the mobiles as they surveyed damage along a mile wide path about 12
miles long.
>
> Kim Elmore, N5OP
--
73, Jerry, K0CQ,
All content copyright Dr. Gerald N. Johnson, electrical engineer
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