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Author Topic: Drone supported stealth antennas??  (Read 94397 times)
ONAIR
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« on: November 08, 2014, 04:17:04 PM »

  OK, this was a shocker even to me.  While tuning around, I happened to come across a few local CBers discussing how to get on the air evenings in HOA antenna restricted communities.  Amazingly enough, one was using a small drone to hold up a wire for a half wave 11 meter vertical!  The flight time was supposedly over 30 minutes, and he would change batteries if he wanted to stay on the air longer.  He even discussed how his next project was to attach a balloon to the drone to keep it up for even longer periods!  Could this use of drone technology have any implications for HOA challenged hams?
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W0BTU
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« Reply #1 on: November 08, 2014, 07:34:34 PM »

Why wouldn't it? That's a great idea, if done right.

I would try to eliminate the batteries, and feed power to the drone via small coax or two twisted conductors. Isolate that power from the RF with a "bias-T".
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ONAIR
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« Reply #2 on: November 08, 2014, 09:09:22 PM »

Why wouldn't it? That's a great idea, if done right.

I would try to eliminate the batteries, and feed power to the drone via small coax or two twisted conductors. Isolate that power from the RF with a "bias-T".
   Good idea!  A powerful enough small drone could also be made to lift a small antenna and cable quite high.  Would be interesting to use with antennas for the VHF or higher frequency ranges.
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W0BTU
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« Reply #3 on: November 08, 2014, 09:38:45 PM »

A potential issue I see with drones to lift an antenna is RFI. Some types of motors generate broadband noise. How common that is in drones, I have no idea.

Another is motor life. Without correct motor bearing lubrication, the motors might fail sooner than expected. It depends on the bearing.

Also, if the motor power was supplied through conductors, remote control and other systems might be unnecessary. Might need some guying (fishing line?).
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W8JX
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« Reply #4 on: November 09, 2014, 10:33:37 AM »

Be much simpler and quieter to use a gallon.
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Ham since 1969....  Old School 20wpm REAL Extra Class..
AA4PB
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« Reply #5 on: November 09, 2014, 10:48:25 AM »

It's still an outside antenna so I don't see how it gets you past the HOA antenna restrictions. The HOA probably also has restrictions against noisy drones. The drone would probably also draw the neighbor's attention to what you were doing. Seems like a simpler idea would be a 1/4 wave vertical in the back yard that could be raised and lowered as needed.
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Bob  AA4PB
Garrisonville, VA
W0BTU
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« Reply #6 on: November 09, 2014, 11:26:20 AM »

Be much simpler and quieter to use a gallon.

A gallon of what, John? You mean a "full gallon" (a kilowatt)? Or did you mean to type balloon?

You need a BIG balloon to lift much weight. IIRC, 8' diameter is the minimum.
Any large balloon (at least the ones I found) are not very durable. They're good for only a few uses, at best.
And, you have to get a helium tank and the fittings.
I bought a big weather balloon for that very purpose. I never used it. (Anyone want to buy it?)


It's still an outside antenna so I don't see how it gets you past the HOA antenna restrictions. The HOA probably also has restrictions against noisy drones. The drone would probably also draw the neighbor's attention to what you were doing. Seems like a simpler idea would be a 1/4 wave vertical in the back yard that could be raised and lowered as needed.

You have valid points. Here's my thoughts, right or wrong.

Drones are temporary. A 1/4 wave vertical in the back yard is more permanent than a drone, and there's HOA restrictions against those too.
And, a 1/4 wave vertical is not for everyone, because hams have widely differing interests. A drone might support an inverted-V, or at least raise a wire vertical (and a couple of wire radials) that's not only less visible, but more effective.

Also, who's going to see the drone at night? Worst case scenario: raise it in the dark, operate, and pack it away when finished.
Even during the day, would a drone 100' in the air look large enough to attract attention?

As someone mentioned above, the drone could raise VHF antennas high enough to make a spectacular difference in VHF coverage. That would be true even if small coax were used. (At ground level, the coax {or even a small balanced line} could transition to large low-loss feedline for any horizontal run from under the drone to the shack in the house.

Are they all noisy? Or more importantly, can they be heard when they're 100' in the air? From watching some drone videos, I got the distinct impression that the ones shown were surprisingly quiet. But I've never heard one. Can anyone tell us?

And another thing I don't know: How much weight will drones lift? I suppose that varies. Anyone know?
« Last Edit: November 09, 2014, 11:29:12 AM by W0BTU » Logged

W8JX
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« Reply #7 on: November 09, 2014, 03:39:48 PM »

A gallon of what, John? You mean a "full gallon" (a kilowatt)? Or did you mean to type balloon?
/quote]

I hate auto spell checker sometimes....  I think that any antenna that required a 8 foot balloon would need a very big noisy drone and it would eat battery quickly with load. Unless you are running a kw you can use light weight wire and a 2 foot balloon. If it is foil coated it will hold helium for several days or if you want to be brazen you could use hydrogen with you can make easily and has more lifting power.
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Ham since 1969....  Old School 20wpm REAL Extra Class..
W0BTU
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« Reply #8 on: November 09, 2014, 04:31:57 PM »

Helium has a lifting force of only 1 gram per liter.
How big the balloon needs to be depends on what kind of antenna and feedline we use.
The higher we go, the more weight we have to lift.
If we use guys, we have to use an even bigger balloon.
If there's a breeze blowing, we need either a bigger balloon and/or guys, because the wind can blow the balloon a considerable distance from center. When that happens, the wire can be at a 45 degree angle to the earth (or worse!), and the balloon is therefore lower as well.

Balloon          Volume        Lifting Power
Diameter (ft)    Cubic Ft          Pounds

1                 0.52               0.03
2                 4.19               0.27
3                14.13               0.91
4                33.51               2.15
5                65.45               4.19
6               113.10               7.25
7               179.61              11.51
8               268.10              17.18
9               381.73              24.46
10              523.63              33.55
11              696.95              44.65
12              904.83              57.97
13             1150.42              73.71
14             1436.84              92.06
15             1767.25             113.23
16             2144.79             137.42
17             2572.60             164.83
18             3053.82             195.66


I like the idea of hydrogen and an aluminized mylar balloon.
« Last Edit: November 09, 2014, 05:00:23 PM by W0BTU » Logged

NC5P
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« Reply #9 on: November 09, 2014, 06:35:33 PM »

I've used helium weather balloons and they work if there is no wind.  Otherwise they go downrange and drop altitude in the process.  Your wire would end up over the street or worse yet over a power line.  The drone idea is better as they could compensate for the wind at least.  I have thought about the tethered drone for some time now being that I can't get on the air except at VHF.  There are problems with powering it over the wire.  The easiest would be to put a DC-DC converter in the drone and use a higher voltage feed over the wires to it.  One would have to use a very good shielded enclosure and filter to eliminate the noise from the switchers inside.  Needs to be very light as well.  I would suggest the bulkhead feedthru capacitors as they seemed to work quite well in my former days designing power supplies for the military.  SMD caps with the multiple (side grounds) terminals are another option if you layout the circuit right and are very careful.  One might consider using a separate loop rx antenna due to the noise on this antenna.  You can put power onto the antenna lines using large chokes on the ground side.  It should be possible to go all the way to 160 meters with the idea as long as the wind isn't too strong.  I would not recommend using except at night, painting the drone flat black so nobody sees it.  The motors do get hot though so if there are police helicopters with FLIR cameras in your area they will see it and may react accordingly (not a good thing).  I wouldn't fly it here or at my other house because police helicopters do fly over both frequently. 
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W8JX
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« Reply #10 on: November 10, 2014, 05:16:59 AM »

The more technology you add to drone antenna concept the more likely it is to fail with damaging results. They say KISS. Keep I Simple Stupid. Not much to go wrong with a balloon, no RFI, no noise, weather proof and no damage when it falls.
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Ham since 1969....  Old School 20wpm REAL Extra Class..
AA4HA
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« Reply #11 on: November 10, 2014, 05:41:57 AM »

It would be easier to just buy a bunch of the metalized film party balloons and a tank of helium. Each night you fill a balloon, attach your magnet wire to the balloon and let it rise up. Maybe even load a fishing reel mechanism with magnet wire.

In the dark of the evening. A silver party balloon rises up out of your yard and rises 68.3 feet (80 meter quarter wave dipole). You spend a few hours chatting away. Heck, the balloon since it is metalized film even acts a little bit like a capacity hat for the antenna.

Done for the night, "snip" with a pair of scissors. The balloon takes off, trailing a 68 foot long piece of wire.

Woes be to any power lines that this balloon and wire might come across. With so little weight on the balloon this thing could go on for miles before it returned to earth.

The next night, stir and repeat.

Now if it is windy and you have that 14KV line in your back yard, that could be bad.
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Ms. Tisha Hayes, AA4HA
Lookout Mountain, Alabama
K5LXP
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« Reply #12 on: November 10, 2014, 06:20:42 AM »

It would be easier to just buy a bunch of the metalized film party balloons and a tank of helium.

Given the price of helium these days, it's a non-starter.  Not to mention the stuff sold for party balloons is about half air.

A tank of hydrogen is about $50 for a 200ft^3 tank plus tank rental.  More lift than helium but there's the burn hazard if you're not careful. 

Sounds like a lot of trouble and expense to go through to hoist a wire.


Mark K5LXP
Albuquerque, NM
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W0BTU
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« Reply #13 on: November 10, 2014, 06:43:22 AM »

Well, if anyone wants to try a balloon, here's the one I have. Never used (plastic bag inside box with balloon inside never opened). Make me an offer. Photos and text file at http://www.w0btu.com/files/misc/big_kaysam_balloon/
« Last Edit: November 10, 2014, 06:46:48 AM by W0BTU » Logged

W0BTU
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« Reply #14 on: November 10, 2014, 06:50:11 AM »

the stuff sold for party balloons is about half air.

A welding supply firm might have pure helium.
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