I would like to lift a 5/8 wave wire vertical for 160m, using a drone, over my lovely saltwater swamp. The thing must be powered from the ground, capable of being left aloft for a couple of hours while I work DX, and capable of hovering in position with windspeeds of up to 20 kph. IT should also be resistant to RFI from a strong RF (KW) field. Has anyone tried this yet?
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1Consider a Helium balloon with three tethers. A vertical may get atmospherics. – Optionparty Oct 24 '15 at 02:37
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1Helium; why not hydrogen! This antenna is only for transmitting. I use a K9AY for receiving. – VE6MRV Oct 24 '15 at 03:25
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Helium provides lift without the expenditure of power. Hydrogen has a smaller molecule and tends to pass through the membrane trying to contain it. Helium is available at party supply stores. Weather balloons to 8 foot diameter are available online. Hydrogen has a combustion hazard and can burn so quickly it's considered an explosion. Atmospheric static in the form of lightning should also be considered. A grounded metal box containing automobile spark plugs attached & connected to the antenna should attenuate static and lightning, yet not adversely attenuate the transmitting or receiving. – Optionparty Oct 24 '15 at 14:02
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1Well, I tried Helium, and it was a bust. I had 15 large weather balloons but the wind just blew them sideways, and the antenna slumped horizontally over the beach. So that was the end of my helium experiment. – VE6MRV Oct 27 '15 at 18:17
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Hydrogen is a large molecule than helium. https://www.youtube.com/watch?v=24a2XOsoG7k – Bob Brunius Jun 11 '22 at 22:48
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You ask “has anyone tried this”. I'm just back from Pacificon 2015 where Glenn Elmore, N6GN, gave a talk on exactly this topic.
He found that using a helium balloon is not practical for lifting antennas on all but the very calmest of days, since the wind will blow it away from vertical, and as well the helium will leak away quickly enough to make keeping it aloft expensive (though there was some discussion of better balloons).
The problem with actively supporting the antenna using a quadcopter (or dirigible balloon) is battery life — “a couple of hours” is pushing the limits of what is possible with a drone that is free flying and not also supporting an antenna. (The bigger the battery, the more power spent supporting the weight of that battery.)
N6GN's latest work is on powering the quadcopter using RF energy sent up the feed line, on a different band than is being used for communications. I encourage you to visit his site and read about his work, since he's working on exactly what you're looking for.
Kevin Reid AG6YO
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I checked N6GN's website; he is indeed powering his drone by RF, but at VHF frequencies. His technique may not scale down to 1.8 MHz; furthermore, I will only transmit for perhaps a few minutes per hour of operation, so an alternate powering technique (a truly tethered drone) will be required. – VE6MRV Nov 03 '15 at 16:54
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2@VE6MRV The VHF power feed is provided by a separate signal generator; it doesn't constrain the signal you're transmitting. He did talk about making them the same thing, but that's not a requirement for the technique. – Kevin Reid AG6YO Nov 03 '15 at 17:45
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1You're right! I looked at his slide deck, and he is indeed using 146 MHz simply to power the drone. Unfortunately, he does not include any 'fabrication details'; as a non-EE, I will need those to implement his ideas. – VE6MRV Feb 11 '16 at 17:04
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Ditch the drone idea, that's going to be way too expensive. You're better off getting a bunch of PVC pipe, sticking it in the mud, and guying it every 25 feet.
Daniel
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@netom Because 100 meters of wire will have too much voltage drop unless it's at insane voltages, and even then you'll get crossover from the antenna, and it'll interfere with the radiation pattern, and probably mess up the drone. – Daniel Feb 01 '17 at 17:08