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Experiences with kite-supported wire antennas
A kite is the cheapest way to get good antenna height without spending money on a tower. Used since the early days of radio they are particularly suitable for portable activity on low
and medium frequencies. This is both because of their long wavelengths (it being difficult to otherwise support a full quarter wave on a band like 160 metres) and their groundwave propagation properties
which favour vertical antennas.
A few notes and tips:
* Use a wire length between 1/4 and 5/8 wavelength on your operating frequency. Much longer than 5/8 wavelength isn't worthwhile as radiation angle increases and lobes split up and become narrow. This is
likely to increase variations as the kite blows around. Too short a wire is less efficient and requires greater attention to ground or radial systems which can be time-consuming to set up if transmitting
from a temporary location. Something like 50 - 60m works well for 160m.
* The wire length does not have to be resonant. But you will need an antenna coupler between it and the transceiver. An L-match with a wide matching range is a good choice, with a good selection described
here.
* I've had good results with stranded insulated wire as it's flexible and not brittle. A 100 metre roll is enough to start you off.
* To avoid breakage to the wire you must have a kite string to pick up most of the pull of the kite. It's no good just relying on the antenna wire to hold the kite. A benefit of this is that you can
have the antenna wire drop straight down and behave more like a vertical. You may need to occasionally tighten and loosen the string to ensure it accommodates most of the tension.
* The support string for the kite can be tied off on a secure object rather than held. I've used a seat or the fence railing of an oval, provided that the wind direction is favourable.
* To keep the antenna wire's average height high, even if the kite is low, a 9m squid pole can be helpful. In this case the wire is fed via the top. The pole provides some spring action which helps absorb
wind variations. But be careful, I've broken poles doing this if tension on the wire is too great.
* Avoid operating in thunderstorms for safety. A kite supported wire antenna can pick up high voltages due to its height and length. You also want to be a fair distance from trees so the kite doesn't
get stuck in them.
* It's important to have a bleeder resistor across from the antenna lead-in to earth. This can be a high value of several hundred kilohms to 1 meg (not critical). This shorts static to earth and prevents
damage to your receiver's front-end. I've had receivers damaged even in non-stormy weather due to failure to observe this precaution. You could even build the resistor into your antenna coupler.
* I haven't had much success with box kites, although others have. The kite type in the videos flew well provided it was fed well (like antennas!). If set up it can hold the antenna wire up in the air
for a long time (eg >1 hour) with minimal operator intervention. If you're in the
UK a SOTABeams kite, designed specifically for radio antennas, could be worth trying.
The videos below illustrate my experiences with cheap ($6) Aldi supermarket kites.
This video shows a test of a Skyfoil kite generously sent by John KC0KBG
Items were chosen for likely usefulness and a satisfaction rating of 4/5 or better.
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Books by VK3YE
Ham Radio Get Started (USA)Australian Ham Radio Handbook (Aust) More Hand-carried QRP Antennas 99 things you can do with Amateur Radio Getting back into Amateur Radio Illustrated International Ham Radio Dictionary Make your Passion Pay (ebook writing)
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