[aprssig] Field Day balloon repeater - question
ky1k at pivot.net
Sat Jun 25 11:18:52 CDT 2005
>I've been looking at using balloons or kites as platforms for temporary
>digipeaters to use in remote areas in support of search and rescue events.
Free ranging balloons drift with the wind, although the ability to control
the height of a balloon can minimize the effect. Above the altitudes
necessary to achieve a gain in range on vhf however, there is not much
control. The ability to minimize drift only happens in the very lowest
altitudes and drift will still be miles or 10's of miles per hour at best.
People who launch propane powered balloons for manned flight have alot of
knowledge of this type of operation.
Kites are more practical, though not for the weak at heart. The problem
here is that even a moderate change in wind direction (10 or 15 degrees)
makes a big drop in the lift until the kite realigns with the new wind
direction. Short term (sudden) wind changes are inescapable.
Very large kites can fly in low to moderate air speeds and lift real loads
however. Launching them is the hardest aspect of their use...at ground
level, the wind is scattered by ground obstructions and lift is difficult
to get. Once above the tree tops, the ground effect is less prevalent and
you get cleaner air.
IF (and that's a BIF IF) you can get a 30 to 50 square foot area kite off
the ground, it can lift 4 ounces per square foot of load in low wind
situations. To do it, and to keep it up, you need a means of controlling
the lift, which is usually done by remote control by changing the attack
angle of the lifting surface. It can be done, and you can keep them in the
air for days....but they will tend to come down as weather fronts pass and
the wind direction changes abruptly, wind that changes direction every 30
seconds will bring anything down.
In WWII, they flew manned kites to fairly high altitudes to observe the
horizon for water based attacks in Hawaii. These were much more dependable
than early radar was in those days. There are some websites with
information about the WWII manned kite flights on the web.
There is also a group interested in EXTREME kite flying......at altitudes
up to 5,000 feet and requiring FAA notification. To the best of my
knowledge, none of these groups involve amateur radio though.
Googleing should turn them up links for you.
Before leaving the topic, the government had plans to launch tethered
balloons along the Mexican border for security reasons. A tethered balloon
might meet your needs for short term disaster scene deployment to
facilitate emergency communications. Googleing should turn up these links
as well. I don't know if the system was ever funded however.
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