The Ohio State University radio club (W8LT) used a balloon supported
vertical for the 160 contest for several years in the late 70's and
early 80's. We usually used a 1/4 wave wire, supported by a
"Kytoon", which is a brand name for what you describe as an
advertising balloon (it's an oblong balloon with fins, like a
mini-blimp). Overall, the antenna worked quite well and produced some
good scores. We did try a 5/8 configuration one year, but it didn't
appear to be any better than the 1/4 wave and suffered more from
windage. The Kytoon definitely works better than a weather balloon,
but neither works well in more than a light wind. We also had the
problem of the balloon losing helium and accumulating frost, so the
wire was often sagging by morning.
I don't believe we ever tried a 1/2 wave configuration...instead, we
just installed the antenna over ideal ground (the 2.5 acre aluminum
ground plane at the OSU radio telescope...see the cover of the 1990
ARRL Handbook for a picture). The balloon era ended one year when the
wire broke and the Kytoon escaped.
73,
/gary
K8LT
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