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eHam Forums => Antenna Restrictions => Topic started by: ONAIR on November 08, 2014, 04:17:04 PM



Title: Drone supported stealth antennas??
Post by: ONAIR 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?


Title: RE: Drone supported stealth antennas??
Post by: W0BTU 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".


Title: RE: Drone supported stealth antennas??
Post by: ONAIR 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.


Title: RE: Drone supported stealth antennas??
Post by: W0BTU 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?).


Title: RE: Drone supported stealth antennas??
Post by: W8JX on November 09, 2014, 10:33:37 AM
Be much simpler and quieter to use a gallon.


Title: RE: Drone supported stealth antennas??
Post by: AA4PB 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.


Title: RE: Drone supported stealth antennas??
Post by: W0BTU 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?


Title: RE: Drone supported stealth antennas??
Post by: W8JX 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.


Title: RE: Drone supported stealth antennas??
Post by: W0BTU 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.


Title: RE: Drone supported stealth antennas??
Post by: NC5P 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. 


Title: RE: Drone supported stealth antennas??
Post by: W8JX 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.


Title: RE: Drone supported stealth antennas??
Post by: AA4HA 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.


Title: RE: Drone supported stealth antennas??
Post by: K5LXP 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


Title: RE: Drone supported stealth antennas??
Post by: W0BTU 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/


Title: RE: Drone supported stealth antennas??
Post by: W0BTU 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.


Title: RE: Drone supported stealth antennas??
Post by: W8JX on November 10, 2014, 06:57:37 AM
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. 

No more burn hazard than gasoline or propane. Inside a balloon, hydrogen cannot burn without oxygen. Also hydrogen is easy to make and in some places easy to get too where there is hydrogen fueling stations. Better lift than helium too. As far as wire crossing a power line when cut free, a thin wire might cause a brief flash when it vaporizes but that's about it. 


Title: RE: Drone supported stealth antennas??
Post by: W0BTU on November 10, 2014, 07:07:17 AM
FWIW, from http://www.barrygray.pwp.blueyonder.co.uk/Tutoring/BBuoy.html:

The density of helium at sea level and 15oC is about 0.18 kg/m3, compared to 0.09 kg/m3 for hydrogen and 1.22 kg/m3 for air. The difference between the density of helium and that of air is therefore about 1.04 kg/m3, so a 1000 kg helium balloon will need about 960 m3 of helium to lift it - this will fill a spherical balloon with a diameter of about 12.2 m. A useful rule of thumb for helium balloons and airships is that at sea level 1000 m3 of helium will lift about a tonne.

Although helium is twice as dense as hydrogen its lifting capacity is only slightly less because what matters is the difference between its density and that of air. Nevertheless a balloon, and in particular an airship, designed to be filled with hydrogen will not work if it is filled with helium, although a balloon or airship designed to be filled with helium will work if it is filled with hydrogen.


Title: RE: Drone supported stealth antennas??
Post by: W8JX on November 10, 2014, 08:17:21 AM
FWIW, from http://www.barrygray.pwp.blueyonder.co.uk/Tutoring/BBuoy.html:

The density of helium at sea level and 15oC is about 0.18 kg/m3, compared to 0.09 kg/m3 for hydrogen and 1.22 kg/m3 for air. The difference between the density of helium and that of air is therefore about 1.04 kg/m3, so a 1000 kg helium balloon will need about 960 m3 of helium to lift it - this will fill a spherical balloon with a diameter of about 12.2 m. A useful rule of thumb for helium balloons and airships is that at sea level 1000 m3 of helium will lift about a tonne.

Although helium is twice as dense as hydrogen its lifting capacity is only slightly less because what matters is the difference between its density and that of air. Nevertheless a balloon, and in particular an airship, designed to be filled with hydrogen will not work if it is filled with helium, although a balloon or airship designed to be filled with helium will work if it is filled with hydrogen.

Real world Hydrogen has about 8% more lift and that could easily offset using better balloon material and still having same or more usable lift than Helium with a lower quality and lighter balloon.


Title: RE: Drone supported stealth antennas??
Post by: WA7PRC on November 10, 2014, 06:15:23 PM
This is what I've learned from reading about Helium balloon-supported verticals...

"Party Helium" is 50% air. If you buy Helium from a welding supply outfit, it'll be nearly pure.

Balloon materials:
Mylar
Pro: Lightweight, seals well
Con: Does not handle overpressure well - easily bursts
Latex
Pro: it easily stretches to accommodate changing pressure w/ changes in temperature
Con: its porosity causes Helium to escape over time. Heavy, compared to Mylar.

Baloon shape/size/number:
1) A single round balloon at the top is the worst application -- it tends to lay over in light breezes. A disc below the balloon helps minimally.
2) Multiple round balloons attached to the rope/wire tend to fly slightly closer to vertical in light breezes.
3) A 'Kiteoon' tends to orient itself into the wind. Its design adds lift with increasing wind.

I've seen all types used in advertising.  The Kiteoons seem to fly the closest to vertical. They also appear to be not inexpensive but could be a good candidate for portable/FD use. Everything attached to the balloon needs to be lightweight. I would use something like small gauge wire-feed welding wire (copper-covered steel), connected to RG-174/U coax (0.1" OD, copper-covered stranded steel center conductor). The coax can handle up to about 100W as long as the duty-cycle and VSWR aren't too high.

All of the above may still be contrary to a HOA contract.

vy 73,
Bryan WA7PRC


Title: RE: Drone supported stealth antennas??
Post by: K4PIH on November 20, 2014, 10:08:33 AM
Ya'll do know that aluminized Mylar balloons are required by law to be tethered? The wire would keep it tethered, but if it gets loose or you cut it and it gets into a power line, you could be liable for damages to the power company, not to mention the danger factor. When you buy those balloons at party places they always come with enough weight to hold them down due to the danger factor of them getting into power lines.


Title: RE: Drone supported stealth antennas??
Post by: IZ5PQT on November 23, 2014, 03:48:38 AM
The serious safety problem with power lines could be the hanging wire. So the antenna wire should never be cut.


Title: RE: Drone supported stealth antennas??
Post by: K5TED on November 23, 2014, 08:39:45 AM
  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?

Amazingly, this sounds like a load of hooey...





Title: RE: Drone supported stealth antennas??
Post by: N5PZJ on November 24, 2014, 05:46:07 AM
  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?


Sounds more than a load of Hooey!!!!   11 Meters, a cesspot of great ideas!?   Nope, drones would have to lift substantial weight, over 5 lbs is not happening!!!! 


Title: RE: Drone supported stealth antennas??
Post by: NR9R on January 21, 2015, 12:11:30 PM
I'll just add that if the objective is to be discrete, even a small quadcopter produces a noticeable amount of noise, sounding like an electric weed wacker.  It would, without a doubt, bring more attention to the antenna.  I think people usually assume they are being video recorded when they see these things too. So...no.     


Title: RE: Drone supported stealth antennas??
Post by: W5SNM on January 23, 2015, 02:58:10 AM
There was a story on the news last night of a drone crashing down in someone's yard with a 6 lb. brick of crystal meth attached to it.   Guess some folks were trying to send it across the border and the motors gave way due to the weight.   Anyhow, the drone was three feet across and runs about $1400 bucks and will hold less than 5 lbs. (specifically a camera).   Seems like a drone capable of holding an antenna would be a high enough cost that a better option could be found.   


Title: RE: Drone supported stealth antennas??
Post by: KK5DR on February 03, 2015, 06:35:59 PM
Even better idea! Use a quad drone capable of lifting a few pounds, help deploy a thin wire antenna up in to the high tree tops after sunset. Then pull the wire back in before the sun comes up. No body would ever know you had an antenna up.


Title: RE: Drone supported stealth antennas??
Post by: W8JX on February 04, 2015, 04:32:16 PM
Even better idea! Use a quad drone capable of lifting a few pounds, help deploy a thin wire antenna up in to the high tree tops after sunset. Then pull the wire back in before the sun comes up. No body would ever know you had an antenna up.

Better have a long extension cord to power it and hope RF does not crash it and no one notices the droning noise of props. I balloon would be WAY better here. 


Title: RE: Drone supported stealth antennas??
Post by: AE5J on February 07, 2015, 09:20:44 PM
Better have a long extension cord to power it and hope RF does not crash it and no one notices the droning noise of props. I balloon would be WAY better here. 

The nincompoop meter has soared off into the stratosphere!


Title: RE: Drone supported stealth antennas??
Post by: AE5J on February 07, 2015, 09:36:50 PM
Even better idea! Use a quad drone capable of lifting a few pounds, help deploy a thin wire antenna up in to the high tree tops after sunset. Then pull the wire back in before the sun comes up. No body would ever know you had an antenna up.

Actually go look at the 26 ga wire (part #534) sold by The Wireman. It is so tiny you could leave it in the tree permanently. I have used it and you have to look real hard to see it in the clear from 15 feet away. Run up into a tree it would be as close to invisible as you could get.

Here http://www.antennalaunchers.com/antlaunching.html. is an antenna launcher that will put your wire over the top of a 130-200 foot tree. No drone needed. To top it off, if you crash a drone in that same treetop, you're going to need some serious help getting it down. Good luck.


Title: RE: Drone supported stealth antennas??
Post by: W8JX on February 08, 2015, 06:19:41 AM
Better have a long extension cord to power it and hope RF does not crash it and no one notices the droning noise of props. I balloon would be WAY better here. 

The nincompoop meter has soared off into the stratosphere!

Yes it has when someone suggests using a drone to support a antenna..