Chapter 4: Kites and Balloons

In 1901, Marconi flew a kite-supported antenna in Newfoundland and
made his pioneering trans-atlantic reception of signals from England.
Hey, if it’s good enough for Marconi, it’s good enough for me! Kites
and balloons give mediumwave experimenters a chance to use larger and
more efficient vertical antennas. While you might not want to go to
the trouble of using a wire antenna lifted by a kite or balloons all

kites

photo: kite used for
first trans-Atlantic reception

An article in the March 1981 issue of QST written by John
Belrose describes his experiments with Parafoil kites. The Parafoil
is shaped like an airplane wing and tends to hold itself level,
so flying it requires little effort if the wind is steady. Belrose
used braided bronze fishing line as his combination antenna wire and
kite tether; this wire has a diameter of about 0.032 inch (0.18 mm).
It seems likely that any kind of braided (multi-strand) wire could
be used, provided it is strong enough to endure the whipping and
pulling it will be subjected to. The wire is more likely to break if it
contains any kinks, splices, or solder joints. Belrose’s article
describes antenna matching circuits for 1/2-wavelength antennas for the
3.8 MHz ham radio frequency.

balloons

Balloons have also been used by hams, Part 15 experimenters, and
low-power broadcasters. Andrew Yoder’s book Pirate Radio briefly
mentions Radio Animal’s experiments with this technique, and articles
in the April 1940 and March 1947 issues of QST discuss ham radio
applications. Any helium-filled balloon or combination of balloons is worth
a try. The small balloons sold in party supply stores don’t have much
lifting capacity, so you might need a dozen of them to lift a significant
length of antenna, and you would probably want to use the smallest wire
that could stand the strain. (Although smaller wire has higher resistance
and makes a less efficient antenna). Larger balloons may be available
locally or by mail order from places that sell novelty items or scientific
equipment.

It’s true that hydrogen, a gas which is lighter than air, can easily
be made by passing an electrical current through water. However,
hydrogen is explosive. Antennas sometimes develop high voltages or have
static discharges at their ends, so you should avoid the temptation to use
hydrogen in your balloons unless you want to have a small-scale
re-enactment of the Hindenburg disaster.

If there is very little wind, a weather balloon (of the type
used to carry meteorological instruments aloft) can be used. According
to Belrose, these balloons are useless in windy conditions.

Perhaps the most enjoyable way to use a balloon would be to ride
in the gondola of a hot air balloon, with your antenna dangling underneath
you. There are some places where you can pay for a ride in a hot air
balloon (if you don’t happen to own one), so maybe this technique could really
be used for short transmissions on special occasions. Maybe you could
even experiment with an upside-down vertical grounded antenna, in which
the ground radials are located above the vertical radiator!

antenna system details

You can measure out 1/4, 1/2, or 5/8-wavelength of wire for
your frequency, or just spool out whatever amount of wire your kite or
balloon(s) can lift. For best results, rig up some sort of ground
system (whether it be radials or a copper ground rod driven into the
earth), and use an antenna tuner to match the transmitter to the load. If
you are operating on a beach or lake-shore, some non-insulated radials placed
in the water might turn the entire body of water into a ground plane for
your antenna. Be flexible; experiment with what’s available.

safety tips

Depending on conditions, your antenna can build up a huge charge of
static electricity. This charge can hurt you or damage your equipment.
Install a resistor between the bottom of the antenna and a ground rod to
bleed off this static charge. Try a 10,000 ohm power resistor, e.g. if
you have a half-watt transmitter, use a resistor rated at 1 watt. Some
people prefer to use a radio-frequency choke instead of a resistor.

Never use a kite- or balloon-supported antenna near
power lines, when thunder and lightning are present, or in the flight-path
of airplanes. If you’re using a large kite, you might need to rig up
some sort of winch to bring the kite down when you are done. Whatever
happens, don’t panic and release your antenna into the environment; it
might cause an accident when it comes back down to earth.