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Kites and Balloons














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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 the time, it can certainly be fun to try on special occasions.
 
Kites

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                                   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
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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.

 
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