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Coiled Antenna

Old 09-25-2007, 03:29 PM
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Don41
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Default Coiled Antenna

I ordered in another Hitec 8 channel receiver (72Mhz) and was surprised to see instructions on how to shorten the antenna by 18 inches thru use of a bobbin. Is this part of new technology or has it been around for a long time?

I'm a big chicken so, factory recommended or not, I'll continue to extend mine all the way (:-)
Old 09-25-2007, 05:05 PM
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Default RE: Coiled Antenna

No, it's not new, reducing the physical length of an antenna by inductively loading the base (effectively what you are doing by winding it round a bobbin) has been around for almost as long as radio.

Whilst the theory is sound, it is notoriously difficult to exactly predict antenna performance due to the number of variables involved. I would certainly recommend that wherever possible the antenna should be extended fully.

Terry
Old 09-25-2007, 07:14 PM
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Don41
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Default RE: Coiled Antenna

Thanks terry. My planes usually run on the large side so I'll continue to use my old way. Surface at the wing's trailing edge and shoot up to the fin tip.
Old 09-25-2007, 08:04 PM
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Default RE: Coiled Antenna


ORIGINAL: Don41 I ordered in another Hitec 8 channel receiver (72Mhz) and was surprised to see instructions on how to shorten the antenna by 18 inches thru use of a bobbin. Is this part of new technology or has it been around for a long time? I'm a big chicken so, factory recommended or not, I'll continue to extend mine all the way (:-)
refer to answer to a previous similar question: What is purpose of the Antenna Bobbin? and sub section "Antenna - Rubber Duckie, Micro & Whip Flywire - replace long aerials with loaded base antenna" on my web page.
Regards
Alan T.
Alan's Hobby, Model & RC FAQ Web Links

Old 09-25-2007, 10:34 PM
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majortom-RCU
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Default RE: Coiled Antenna

I was introduced to coiling the antenna wire by a pylon racer, who told me it was common practice in their sport, since the planes are not all that big and drag reduction important. I gave it a try on one of my sport planes, and just for the heck of it compared range checks with antenna coiled vs fully extended. The range was a lot better with full extension, but adequate with it coiled. Pylon racers naturally stay as close as they can to their designated course for best times, so extended range not a concern.

As long as the model is in the air, it's amazing how little radiation power will go a long way--to the point where the model is a tiny speck, indecipherable to the eye, but still controllable by the radio. More than once, I've flown a full tank with my antenna retracted (not on purpose, of course). Back during the CB radio craze I found that if I drove to the beach and monitored the fishing boats I could get better reception 30 miles over the water compared to a few miles in the city.

I've also set up a few models with the antenna running around the periphery of the radio compartment and then to the tail to keep everything inside the model. That also works. But take care to fix the antenna to the frame somehow so that it doesn't just collapse into a jumble.
Old 09-25-2007, 11:27 PM
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Don41
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Default RE: Coiled Antenna

I use the super sticky wing saddle foam to hold the antenna in place. It has never let go. I always take as direct a shot out of the cabin as is possible but I have never run any tests on the effects of other configurations.

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