Sky Anchor Puts Radios Up High, No Tower Needed

When it comes to radio communications on the VHF bands and above, there’s no substitute for elevation. The higher you get your antenna, the farther your signal will get out. That’s why mountaintops are crowded with everything from public service radios to amateur repeaters, and it’s the reason behind the “big stick” antennas for TV and radio stations.

But getting space on a hilltop site is often difficult, and putting up a tower is always expensive. Those are the problems that the Sky Anchor, an antenna-carrying drone, aims to address. The project by [Josh Starnes] goes beyond what a typical drone can do. Rather than relying on GPS for station keeping, [Josh] plans a down-looking camera so that machine vision can keep the drone locked over its launch site. To achieve unlimited flight time, he’s planning to supply power over a tether. He predicts a 100′ to 200′ (30 m to 60 m) working range with a heavy-lift octocopter. A fiberoptic line will join the bundle and allow a MIMO access point to be taken aloft, to provide wide-area Internet access. Radio payloads could be anything from SDR-based transceivers to amateur repeaters; if the station-keeping is good enough, microwave links could even be feasible.

Sky Anchor sounds like a great idea that could have applications in disaster relief and humanitarian aid situations. We’re looking forward to seeing how [Josh] develops it. In the meantime, what’s your world-changing idea? If you’ve got one, we’d love to see it entered in the 2020 Hackaday Prize.

64 thoughts on “Sky Anchor Puts Radios Up High, No Tower Needed

  1. “Let me first say I do not like the word “Drone” to describe multi copters as it is negative and improper.” – Description from project.

    Very fitting that it is in the “Drone hacks” section, lol.

    1. Ha. I don’t think they’re going to get that to stick. Good try, though.

      By the way: hackers wear hoodies and balaclavas and break into computers to do crimes ;) sorry everybody, it ain’t gonna happen

      1. So, take a gander in the googles and you will see this is already a thing, in this case it is just smaller , cheaper, open DIY and more available than the larger units.

    2. I still remember when Fox News did the story on ” the danger of drones” comparing them to the predator military drone as if DJI just started handing out mini nukes with propellers.

  2. Not to diminish his work but wouldn’t it be a lot easier to use balloons to at least assist with the heavy lifting? I also suggest an emergency cable release in the event that it gets too far out of place, lest you hit a power line.

  3. I was trying to figure this out with small blimps but haven’t yet solved the kiting problem, (changing orientation due to wind, and hence maintaining desired antenna alignment) Which although likely to be lessened in a full controllable craft such as this, may still rear it’s head due to unpredictability of wind strengths and changes.

    I was looking at this project yesterday and wondering why the heck it’s burdened with a data link cable. The drone is in clear line of sight overhead, surely 5Ghz networking hardware isn’t as heavy as meters of cable, or laser links would be possible also. Also the ethernet over power line stuff could be adapted to reduce cable load.

    Myself, I’d do it with “lamp cord” for power and motors rewound to 110V DC, power sent as AC line voltage with a regulator “upstairs”. Anywhere that has “got power” worth tapping into and not merely charging from has “got power” and a few hundred watt sine wave inverter isn’t expensive these days if you’ve just got a bunch of DC watt hours.

        1. I mean yeah it does keep it “in the neighbourhood” pretty well, but it still will have a lot of freedom to dance around. if the wind was blowing right from the direction of one of the lines, if strong enough, (or it was cool and the lift of the blimp was weak) it could swing on an arc around that line, losing some height and letting the other lines go slack.

          1. I actually investigated this very concept as a way to haul up an HF antenna for Ham radio (I am a ham radio operator) for a verticle dipole in 160m. The drone would have been pretty large necessating a tether capable of transferring 7+kW just to power the drone.

            I had thought about a power system that imposes a DC current on the tether as well as using the tether as the antenna. High power (1.5 KW for Ham signal common mode) rf and 7.5 KW dc on same cables necessated the dc voltage be very high (1000+ volts) to make the cables light enough for the drone to loft them. The filtering devices necessary to extract the dc power, block the rf, and still be light enough for the drone to still fly were formidable challenges. It would be necessary to build some very light weight custom rf and power equipment as nothing commercial and off the shelf exists.
            Still a fun engineering exercise. I wish you luck in your endeavor!

    1. Well, the drone itself has to get power from somewhere so unless you’re going to beam that wirelessly as well, you’re going to need at least the power cable. And since you’re stuck with it anyway, adding a couple optical links to that should be only a small jncrease in mass in exchange for simplicity, speed, and, quite importantly, a cleaner RF spectrum!

  4. The limitation on this is going to be motor lifetime. Your typical commercial drone motor lifetime is in 10s or 100s of hours. Far, far from continuous use.

    The second limitation will be how much wire you can lift. Wire is heavy.

    You don’t need computer vision for positioning with GPS already onboard. It’s precise enough. Unless you are designing for armageddon, where GPS gets turned off. Get it flying first :-)

    Most people use balloons for this. And have since radio has existed. They worked well with long-wire antennas, as do kites. But there is the risk of hitting a power line and draping a live wire over hundreds of feet.

    1. That’s kinda what I was wondering – why bother with this since balloons exist? I mean it’s neat from a project point of view, but from a practical point of view, seems like the wrong way to solve the problem.

      Just have a light tether, a few thin cables for communications and power, and a balloon. You don’t need perfect stationkeeping – the entire point of this is to broadcast a signal over a large area.

    2. GPS is even a bit pointless when it can’t go very far due to the tether. You could get it to center with a semi analog system where you broadcast a beam like the old aircraft navigation beams, only weak and straight up and it would try and ride the directly overhead null, not the tones either side. I think I’ve got a kids game like that in an old circuits book, uses beat frequencies.

        1. Because maybe it would smack itself to death on the walls of a canyon you were trying to communicate from before it figured out where it was. More I use GPS, less I trust it.

    3. Orrr….. you don’t need much smarts in the airframe, because you could use a ground based control system, keep the blob in the middle of the frame style, upward pointing camera. I’m assuming it would carry RC gear anyway for manual override. Also modern RC gear is tiny and I think a full system weighs less than anything smart enough to use computer vision plus a GPS.

      However, if this is all a McGuffin just to play around with machine vision… proceed.

    4. I think your estimate of brushless motor lifetime is way too low. Assuming the motor isn’t overheated, bearing wear would be the next likely cause of failure. While poor-quality bearings may be common, this doesn’t mean that all bearings are poor quality, and decent ones can last thousands of hours.

    5. That was my first thought, the motors on the drones are built for intermittent use, and as you said, wire is heavy. You also have wind drag on the wire going to the drone. It is an interesting idea, and it may be useful for situations that require occasional, long range check in’s. Launch the antenna, send the message and take it down.

      1. An easier solution, unless you need dozens, hundreds, or kilowatts of power. strip down two handitalkies and build a repeater from them. HTs like the baofeng light up their baclights/keypad lights when squelch is broken. Could use that with a simple circuit to push the PTT button on the other radio. Stripped of their casing and individual batteries, these would add little weight to a drone. The two HTs could probably be run off a shared battery, or tap into the power system of the drone. Possible there are already HTs that have a repeater function in them, but are they as cheap as two baofengs?

  5. There used to be an emergency radio in life rafts, which was a Morse radio sending sos messages when the hand powered generator was working. A kite was tethered to the antenna in order to give it some time. That system existed 40 years ago. I can’t find any details or reference on the internet. Using a kite seems to be a good way to put an antenna up high.

    1. Kite seems like a bad idea. You’re reliant on enough wind to loft it up. Seems like a better idea would be some kind of balloon with a small canister of pressurized helium/hydrogen. Like the CO2 carts that BB guns use. The canisters should hold the helium/hydrogen near indefinitely and could be dispensed into the balloon at time of need. Tether it with a length of magnet wire to be used as an antenna.

  6. I appreciate the novelty of this, but the cost and reliability of such a device is going to be pretty low for the stated purpose. Any adverse weather conditions and you’re sunk. Those motors also have a very finite lifespan, usually in hundreds of hours. It’s also going to be noisy and take a fair amount of power to maintain.

    If you heat air by 100 degrees F / 45C, it weighs about 7 grams less. Therefore, each cubic foot of air contained in a hot air balloon can lift about 7 grams.

    The drone has a lifting capacity of about 2.4kg as is, so 343 cuf of air would be needed to provide the same lift capacity – conveniently exactly 7ft x 7ft x 7ft or a sphere of about 4.35ft radius. I know that these aren’t the correct ways to measure a balloon, but this is just for conceptual reference of size.

    For redundancy / safety, you could use 4 balloons of about 2.75ft radius each, that way if one goes for some reason your payload can just gradually return back to earth, and you could probably detect this and automatically crank up the heaters in the remaining balloons to compensate / bring it down safely.

    I would think that this would be a much better, cheaper, and more reliable way to do this, and you don’t really care about exact stationkeeping. The purpose is to broadcast over a distance. Worst case you include GPS and an accelerometer onboard, and then aim your antenna accordingly.

    You can get creative with the gases used based on what’s available. Assuming helium isn’t practical, you could generate hydrogen via electrolysis pretty easily (of course that brings a large host of other dangers), or just air with 100% humidity to help give it a boost.

  7. Maybe it’s just me but I think people are missing the idea of this project, although a balloon may be better it’s also more cumbersome, with the “sky anchor” the drone it small and can be run off the same power you need for your radios, so is it better than a balloon? Maybe not. Is it more convenient? Yes.

    1. Given the usual power consumption of radios in emergency scenarios, and comparing that to what a drone typically requires, you’d run out of radio juice *really fast* if you tried using the radio batteries for the drone. That said, if you only need a short exchange, throwing an antenna drone up, exchanging data and bringing it back down would definitely be more convenient than using a balloon, so you have a point there.

    2. I’d still call balloons way more convenient – they are small when not in use and active are floating around up there out the way.. About the only use I can see for this is if the multirotor is battery powered so there are no tethers and its making use of the fact it can move to move (presumably keeping itself centred to the users of its comms hub for minimum transmission power, but perhaps also to do other useful things – disaster relief imaging etc)

      And then I’d use a combustion powered multirotor – as while bigger and heavier than an electric can be the energy density and availability of fuel makes it useful for repeated relatively long flights. I still think in 99% of cases blimps with station keeping or the simple tethered balloons are a better option.

    3. its only “convenient” if you only care about multiple rapid short term deployments, like say a military campaign. but the stated mission (disaster response) that convenience carries so many disadvantages it becomes meaningless.

      1. In many emergency situations an ad-hoc radio tower ends up being constructed. Like in my area recently in Chattanooga TN,just a couple streets from my home, a tornado came through and all communications and power were down. The only way to get communication or data to first responders was to start erecting radio towers, considering there are only used for a week or two maybe, the cost is a huge waste, and it took days to build them that resulted in a lot of lost communication. If my city had say 10 of these the whole area would have the ability to interconnect through radio and data in a matter of a few hours after the disaster. If local firefighters for example were able to keep one on hand they could bring it anywhere needed. The cost of a larger “Drone” tethered UAV being 100,000 or more is not inciting enough for departments to shell out cash from there budget, but what if they could get a similar tool for 3-5 thousand that is smaller, more portable and no one will cry if it becomes damaged during a crisis because of the lower cost.

  8. Is the electronics package RFI / EMI proof ? (given the fact that the sole purpose of the device is to anchor a wire emitting electromagnetic energy / RF at unknown power levels – conduction, radiation of that field will no doubt overlap the platform)

  9. This may be for “pop-up” burst communications in a pandemic or emergency. You pop your drone up at 4PM. Everybody turns on their receivers at 4PM. The drone-tenna blasts out an encrypted zip file and then lands. I think this guy is creating this system for emergencies only.

    1. The intended case is to launch it whenever radio communications are needed, which may not be continuous , but the flexibility is there. In my use case the base station and any adjacent equipment is powered by a gas generator.

    1. Hi Old guy, Tethered drones are now included in part 107 of FAA since 2018. They are treated practically the same, but it does indicate that the aircraft cannot fly over non participants, another words people participating in your function. Which generally this is avoidable by marking off a area around the launch site and only a operator or there participant enters. Previous precedence from FAA established when they are used for firefighting, for example, all the emergency personnel are considered participants and a non issue.

    1. Oh right, an infomercial balloon then, that you don’t have an inflation cylinder for, and accidentally keep popping, and absolutely never carry it ready to go in the back of a van, and people keep walking into it with scissors. “There has to be a better way!”

  10. Circa WWII there was at least one emergency radio, intended for lifeboat use, that was cranked for power, and used a balloon to get the antenna up high.

    I know I’ve read some articles where hams have used weather balloons (those were certainky cheap on the surplus market at one time) to support an antenna, , though no specific articles come to mind.

    I’m sure the military has done more work on the concept.

    1. Hi Michael, military contractors and even the navy have them however they are not available to the general public. There are some tethered UAV companies in the security sector that could be modified to hoist cables for an antenna or internet, but 100,000 just to have a donor to start with is a high price and the units are very large. This project aims to make the same kind technology avail cheaper so DIY and small organizations use them.

  11. I keep thinking about this, because I want to put a camera about 100 ft up, for traffic studies. I dream about a tethered copter, or a tethered electric hot air balloon. I keep coming back to the fact that there’s power lines nearby and dismissing the idea. I’ll dream about it again though.

  12. Commercial solutions already exist for this very purpose! https://floridapolitics.com/archives/278045-flying-cow-brings-cell-service-back-to-mexico-beach

    There’s a big market for exactly this. The point of the drone is for rapid deployment, high elevation, and control in adverse weather. Balloons can’t quite tick all the check boxes, since it requires transporting lighter than air gas (or fuel to continuously heat air), having to anchor in multiple locations, and the ability to do airspace mitigation (you’d expect a lot of medivac helicopters after a hurricane). When you’re looking for getting 25 lbs of cellular gear in the air for first responders, etc, the downsides of the drone (cost to purchase and run, complexity, service hours) can easily be overlooked.

  13. Blimps with radar… https://www.cbp.gov/frontline/frontline-november-aerostats and here s one that most people visiting Flordia’s Key West would have seen: https://www.bigpinekey.com/blimp-fat-albert-history/

    New obstruction lighting rules would also require high systems to contain all sorts of lighting on the tether and drone/blimp that would add additional weight and power requirements. I’m thinking that the regulatory burden can sterilize the viability above a certain elevation.

    Lots of power conversion technology available in telecom at 400VDC to transfer power. Even most 230V AC power supplies will work fine at 400VDC input, except for the regulatory compliance issues with connectors and fusing.

  14. Yes it is very cool to use a (probably pre-existing) copter to bring that wire up to height!
    However, I think the device holding an antenna upright in the air could be a much less complex construction.
    On the other hand, copters are so much a bulk commodity these days that it might be still cheaper to use them instead of a simpler but lower volume “product”.

    1. I will update the product page, but to be clear, heavy radio equipment can stay on the ground and the hexacopter can just lift that. My initial use case it will have WIFI and SDR on board with as little equipment as possible. If hoisting a ethernet or fiber line is too heavy then the equipment on the bottom of the hexacopter could be configured in a repeater type mode. The signal going from the base upward, then from the hexacopter outward, and that same way in reverse as well.

  15. Try a Goubau line… it can drive power and signal over a single wire and save a lot of weight. Or before they shut down… do like the Cyphy Works Parc and use a tiny high-voltage low current pair of wires. They were pushing real time hd video and power over a couple of 32 gauge wires.

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