Amateur (Ham) Radio and RC (Radio Controlled) Flight

[hevans1944]

Years ago, in the 1950s, I was briefly attracted to the fixed-wing, flying, model aircraft hobby. Back then it was all about balsa wood air-frames, and fabric-covered fuselages, wings, and control surfaces, said fabric painstakingly applied, doped, painted, and affixed with decals before the model was deemed airworthy. It generally took several months to complete a model before it was ready for its first flight. Of course the highly toxic fumes from the model dope made it all worthwhile... probably. If you survived the brain damage.

Radio control was possible with the larger models, but very expensive and prone to interference from other nearby RC operators. So most of the non-RC "flying" was done in a circle, using a pair of thin steel cables attached to the port-side wing(s) to tether the aircraft to the operator on the ground, who then controlled the pitch axis of the flying model by varying the differential tension on the two cables. This was the so-called U-Control, patented, method of model airplane flying. In skilled hands it allowed the operator to perform some amazing aerobatic maneuvers within the limitations of flying in a circle. Ho hum. Boring! Plus I never did get the "hang" of how to fly my little Spirit of St. Louis, 0.049 cu.in. glo-plug powered, single-engine model airplane using U-Control lines. Heck, most of the time I had trouble even getting the engine started.

It is all so different today. High-speed, brushless, DC motors and lithium polymer (LiPo) batteries have made liquid-fueled engines virtually obsolete. Inexpensive plastic kits with on-line DIY instructions and Asian RC electronics have brought Unmanned Aerial Vehicle (UAV) capability to the common man. With modern electronics controlling the flight, you don't even have to know anything about flying! What's not to like? Just peel off twenty or thirty Benjamins and purchase a ready-to-fly quad-copter drone with Forward Point of View (FPV) video camera and you are off and running (or up and flying). Be sure to register your drone with the FAA, always fly with the drone in your direct, unaided eyeball, line-of-sight, never fly more than 400 feet AGL (Above Ground Level), and never faster than 100 mph.

The purpose of this thread is to discuss the role (if any) of amateur radio in extending the range and reliability of Radio Controlled (RC) flight. One can apply to the Federal Aviation Administration (FAA) for an exemption to the "line-of-sight" rule, but if granted that still leaves the problem of how to implement a reliable radio link over extended distances, beyond the line of sight, where there may be and probably are obstacles along the way. While it may be as simple as increasing transmit power levels, which a ham license allows, it may also be more complicated, requiring frequency diversity, or more bandwidth to accommodate sophisticated error detection and correction, or spread-spectrum techniques to "punch" the radio frequency signal through between the operator on the ground and the aircraft in flight.

We are not interested in discussing the state-of-the-art capabilities of military platforms such as the Predator drones or Global Hawk remotely piloted vehicles (RPVs) with their satellite down-links and other airborne communication networks. Nor are we interested in the low-power, unlicensed, low-end of the range of civilian users. What I would like to see this thread address is the synergy that can be obtained by merging FCC-licensed amateur radio capabilities with modern RC flight control capabilities applied to FAA-licensed drones. The goal is to advance the state-of-the-art and the enjoyment of both hobbies, safely and legally.

Electronics Point is an eclectic community with a broad range of experience and capability. We are not just all about LEDs and PWM motor control, although there is nothing wrong with that. There are knowledgeable posters here that I have not seen in awhile, so maybe a discussion in this thread will revive their participation...

Hop (AC8NS)

 

[Bluejets]

Once a year in Australia, there is, or at least up until a couple of years back, a competition involving "out of sight" model aircraft.
Legally conducted and supervised .
Do not know of any particular forum offhand that supports the details but I certain there would have to be something somewhere.
I'll do a bit of further checking.

What range are you referring to here?

I did the same model aircraft building and flying as you and returned in the late '80's to choppers, gliders and pylon racing. Did some u control flying just for exhibition as many here had never seen it, especially the combat side of it.
Then honed the rc side with another member doing close position formation flying.
Trouble with that was, he was a bit of a character, and would often point to something to distract me just long enough to swap places. Then when I would point out he was drifting, or worse , he would simply say, no, that's you and then crack up laughing.

 

[Hopup]

2 to 10 watts of control and video + diversity receivers + gps autopilot. Control 433 and video 800 to 1.2 should be good.

 

[Bluejets]

10 watts might stir up a hornets nest.

 

[hevans1944]

...
What range are you referring to here?
....

For all practical purposes with FPV flight control: unlimited range. Fly anywhere until power fails, but I envision a small on-board gas turbine engine to provide electrical power for the prop motor(s) and electronics as well as to keep a smallish battery charged. It would be a creative challenge to develop the gas turbine generator.

 

[Bluejets]

So autonomous to a degree with supervisory control?

There is already a small 3 phase generator unit used for repowering.
Rather than engine driven, works like a cropduster pump with a wing mounted drive propeller.
Not sure of output though.

Think I saw somewhere where one could use a brushless motor as a generator.
Again depends on required output.

Might be some pointers/contacts in this link for the competition in Australia.
https://uavchallenge.org/

 

[hevans1944]

So autonomous to a degree with supervisory control?

From what I have been reading about flight controllers, the "little black box" that actually "flies" multi-rotor UAVs, autonomous flight is now a standard feature. You just upload a mission profile with GPS way-points and take off. The FPV is there so you can see what's going on, but the actual flying is instruments only: accelerometers, magnetometers, altimeters, air speed and attitude gyroscopes, whatever telemetry and control inputs you need for autonomous operation. There are probably (or should be) rules that require a "pilot in the loop" for safety and liability concerns, but this type of legislation is in a state of flux right now as lawyers struggle to keep up with technology. So, yes, "autonomous to a degree with supervisory control" is IMHO both desirable and necessary to safely pursue long-distance flights and long-distance flight control.

The licensed amateur radio part of it lies in the implementation of long-distance flight control, which is what I hoped this thread would address. Many options are available, including distributed peer-to-peer RF networks. Some autonomy is desirable in the probable event of loss of data communication at some point in the mission profile. A fail-safe means, or several fail-safe means, would need to be implemented to allow the UAV to safely return to origin in the event of complete and permanent failure of radio communication. It is my understanding that this is already implemented in high-end commercial UAVs, not just for safety but also to recover the investment in UAV hardware. So amateur radio doesn't add anything to that mix of options, it just extends the range at which they might be needed to recover the UAV.

Might be some pointers/contacts in this link for the competition in Australia.
https://uavchallenge.org/

What an eye-opening revelation for us old fogies of what is going on "down under" in Australia! This annual UAV competition is exactly in the vein of what I hope this thread will become. Kudos to the impressive list of sponsors for lending their considerable support and credibility to this effort.

As a contractor late in the previous century, I used to perform oxygen ion-isolation implants on Northrop Grumman GaAs HBT integrated circuits. I never asked about, and was never offered, any information as to what those circuits were, but it involved a high-energy, high-mass, particle accelerator on my end to deeply implant non-conductive vertical isolation channels through the epitaxially-grown HBT structures, the ions passing through apertures in a relatively thick (for IC production) photolithography mask that N-G applied, exposed, and developed on the wafers before sending them to me. The mask was thick because it had to absorb, without transmitting, high-energy ions that did not pass through apertures in the mask.

Earlier versions of this process, developed in the late 1990s for Texas Instruments and the Air Force Institute of Technology (AFIT) Laboratory at Wright-Patterson AFB used a sputtered gold layer to stop the ions, with the aperture areas removed mechanically by peeling off the exposed and developed photomask, taking with the mask the gold in the aperture areas. Northrop Grumman figured out a way to avoid this tricky and painstaking process by spinning on, exposing, and developing a thick layer of photoresist that didn't require the gold or mechanical removal of the mask. I wound up implanting dozens of these wafers every month for more than ten years, with some breaks in between to perform other implants for other purposes for other customers.

All I had to do for the Northrop Grumman implants was mount the 100mm wafers in a vacuum chamber and scan an ion beam across them, selecting a variety of energies suitable to the ion depth of penetration. Pretty neat work while it lasted, but eventually N-G moved on to larger diameter wafers, which we could not practically implant because of scan-size limitations. But my take-away from working with Northrop Grumman was the impression that they were, and are today, a very competent defense contractor... every bit as good as Lockheed's Skunk Works. Plus they designed and built the Global Hawk autonomous UAVs, currently in service, with an early model on display at the Air Force Museum in Dayton, OH.

One thing I noticed about the Australian UAV competition was the use, by one of the teams, of a "communications drone" that circled one of the way-points to provide an aerial RF "repeater" to extend the range of the ground equipment beyond line-of-sight. Another thing that became quite apparent was the need for greater reliability. Several teams "failed" to complete their mission because of hardware and/or software failures, although there were only one or two "crash and burn" incidents caused by engine failure. Nevertheless, the goal should be, and must be, total reliability. No excuses. No drone company is every gonna make big bux from Amazon drone deliveries without a track record of 100% reliability. Of course, as a hobbyist, your mileage (or kilometers) may differ, but it is never a good idea to settle for "second best" when it comes to flying.

Hop (AC8NS)

 

[Bluejets]

My eldest might be of some assistance to you as well.
He is retired (not by choice but rather political cutbacks) Aus/NZ/UK pilot.
Currently with Insitu Australia (Boeing) in Aus. Have word cut-backs coming there also.
Might be restricted in some respects but.......

Also some control like this also done here ( just example, other content there also covering waypoints etc. etc. .....might be worth a look or maybe a chat to him.

 

[Hopup]

Using quad for long range is very inefficient, if there is need for vertical landing, the choice should certainly be quadplane but that might be obvious.

As for autopilot systems, versatile systems already exist in the very affordable ranges for example eagle tree vector which is excellent piece of OSD/Autopilot/sensor system, still not super high end. If there is need for high reliability then redundant design is obvious choice, backup power for all parts, two overlapping autopilot systems, etc. Also these parts tend to be pretty hot during use so they need pretty good air circulation.

 

[BobK]

0.049 cu.in. glo-plug powered, single-engine model airplane using U-Control lines. Heck, most of the time I had trouble even getting the engine started.

LOL, That was exactly my experiece. The one time I actually got it running, my cousin had the control. He wasn’t very good at it, resulting in a series of steep climbs and dives that ended as you might expect: Nose directly into the pavement at top speed. That was the end of my nodel flying carreer.

Bob

 

[Bluejets]

LOL, That was exactly my experiece. The one time I actually got it running, my cousin had the control. He wasn’t very good at it, resulting in a series of steep climbs and dives that ended as you might expect: Nose directly into the pavement at top speed. That was the end of my nodel flying carreer.

Bob

This is what qualified "instructors " are for.
Was tricky with control line but worked ok.
Quickly learned to control via either hand and any configuration.
Close quarters though and one would hope the student had at least showered in the last day or so.

Best thing to ever come along was the "buddy box" system for training rc and now there is the "no lead wireless " system, even better.

Before this, the instructor would stand close to the student and take the radio back if it looked like problems coming.
Trouble with this was, students always think they know better and I have had times where they would be backing away saying, no, it's ok, I've got it.
Then when the plane or whatever was 3ft off the deck, radio shoved back........here!!!! you take it.

 

[Bluejets]

Hop,
Thought this might be of interest to you.
Merry Christmas......Jorgo
http://ardupilot.org/planner/

 

[(*steve*)]

None of us near Gatwick are we?

 

[davenn]

Hop,
Thought this might be of interest to you.
Merry Christmas......Jorgo
http://ardupilot.org/planner/

yeah, I can do flight plans for my drone like that. Something I have yet to play with

None of us near Gatwick are we?

haha ... I'm innocent ... and I saw they released that couple in England as at the time there was no evidence against them

 

[VenomBallistics]

How did I NOT see this thread
the radio side of things can be finessed with antenna selection rather than forced with raw power.
Not to say there isn't some merit in using both schools of thought.
here's an online calc to take with a grain of salt.
http://www.maxmyrange.com/
Results are optimistic, but do seem legit in terms of comparison.

Propulsion has long been rendered well in computards.
this is another online version you can kick the tires with.
Its paid version is quite good.
https://www.ecalc.ch/

air frames ... we like air frames.
Today, Balsa builds are considered special.
Foam has largely taken over the hobby.
In particular, dollar tree foamboard has become a mainstay in the hobby. This takes a lot of pain out of developing airframes one might graduate to balsa builds later ... or just embrace the mantra of "Build, Fly, Crash, Repeat"
https://www.flitetest.com/
https://www.mesarc.club/
https://www.youtube.com/user/ExperimentalAirlines
https://aerofred.com/

While electric power has mostly replaced internal combustion. It is not always the best option, and I hope to see continued support for it.
You cannot beat the run time of a fuel burner if you intend to do any serious area exploration.
Also, as scale increases, the operating cost starts to favor nitro engines after the 25 range or so.
It's not just the motor, but the batteries to run it that must be considered. Figure three battery packs minimum for the system and even some of the high priced four strokes start looking like a bargain.

 

[(*steve*)]

If you employ gain in your transmit antenna you need to be sure you are pointing the antenna at the drone. Something with 26dbi gain will have a beam width of only 7 degrees. This is possibly a little extreme, but you're going to have to be pointing pretty closely. If you're not, it can be worse than having an antenna with no gain!

Gain on a receive antenna is even trickier. You need to be sure that no likely changes in attitude will cause you to lose the signal. You may even want to have some sort of recovery mode that will search for a signal if it is lost (just adopting a normal attitude may be the simplest method, gaining altitude may be secondary method). Diversity antennas/receivers will also help.

Often omnidirectional antennas with gain are used. These trade vertical beam width for gain, which you need to be careful you don't take too far...

 

[VenomBallistics]

typical setup is a dipole for the control side at both ends so as to avoid dropping out of the TX field as much as possible.
vid side is where we finesse things by "squashing the doughnut".
In a typical 5.8G setup. it's a "pagoda" type airborne and a VAS ION on goggles .... this teamed with a directional high gain if using a diversity RX.

 

[hevans1944]

Thanks, @VenomBallistics, for joining this thread. Your considerable knowledge and experience with UAVs is much appreciated. I haven't had time yet to visit all the links you provided in your first post of this thread, but I will definitely visit all of them eventually.

I started this thread after an inspirational (and hijacked) conversation on your introduction thread, after you expressed some interest in the benefits of amateur radio for longer distance RC flights. At that time, I had no idea what the state of the art is today, only a rather tenuous knowledge of what is possible with deep pockets full of cash. It seems the possible is now within reach of the relatively impoverished amateur hobbyist too, thanks to the wizards in Silicon Valley and other technology hot spots around the world.

Since this is an electronics hobbyist forum, many members may be unfamiliar with Unmanned Aerial Vehicles or UAVs. The terminology used to describe these devices can be confusing as well. I recently found a website oriented towards equipment sales to UAV enthusiasts, which also offers simplified explanations of everything you need to know about Radio Controlled (RC) First Person Viewing (FPV) flight, with an emphasis on multi-rotor air frames. Check it out here.

Back to the subject of antennas and antenna "gain"... since the base or ground-control station is fixed, relative to the flying UAV, there may be some advantage in using a directional antenna if it can be pointed at the aircraft. All antennas have "gain" relative to a hypothetical (but physically unrealizable) isotropic radiator, which radiates (and receives) radio frequency power equally in all spherical directions centered on the antenna. The so-called "gain" of a real antenna is always achieved at the expense of sacrificing signal amplitude in non-preferred directions to signal amplitude in preferred directions. TANSTAAFL.

From the POV (Point of View) of the UAV, the direction back to "home" may be calculable from GPS (Global Positioning System) coordinates, but the UAV antenna orientation is probably not point-able without rotating the antenna or the entire airframe, and possibly adjusting the elevation angle of the antenna "bore sight" axis with respect to the vertical orientation of the UAV. These do not appear feasible hobbyist solutions at this time because of SWAP (Size, Weight And Power) limitations, although perhaps electronically-steered "patch" antenna arrays could be employed.

It appears to me that the only certain and reliable way to increase range is to increase transmitter power on both ends of the link, which only a pilot with a radio amateur license can legally do. We can also play with modulation and data encoding techniques to improve two-way reliability of the command, control, and data (telemetry) links and perhaps move up to digital video for the FPV camera. The key here would be bi-directional packet communication, with packet error correction in real-time with minimal delay, especially for the FPV video link.

 

[VenomBallistics]

You have the antenna gain thing well addressed.
The typical finesse set up of a pagoda and ION pair does sacrifice the unpreferred directions.
Where a dipole "apple" field is the baseline, a Pagoda compresses the field into a "doughnut". That helps its lateral transmission range. The pagoda has established itself as one of the most desirable airborne antennas at present. The ION antenna further flattens this doughnut pattern for even more gain. However, it is so compressed that it does not leave much latitude for pitch and bank when used airborne. It's best as a ground omni.
Where diversity receivers are employed, a uni directional patch or helix is often used on the "B side" so the pilot can turn his head to maintain contact.
It's not the best way to run the Uni side of the system, but where your gear is just aircraft + goggles + control TX It is useful.

A folding tripod can be fashioned into a relay station. This automatically takes a huge chunk of convenience out of the craft and goggles approach, but it allows us to get serious.
You can use a low power link from tower to goggles while the craft to tower link can be a high power system in a lower frequency that'll help punch through the occasional tree or similar obstacle. Also, the tower can be fitted with a tracker that will follow the craft automatically, making the use of a ridiculously high gain uni antenna quite practical.
HD digital systems are also available, But before we get into the things in this paragraph, you better be a solid pilot. If you cannot make the save, you're out thousands of doll hairs when you can't figure out how to get to the crash site.

GPS autopilot ... yup ... got it. My first FPV platform was a second hand motorized sailplane with such an autopilot onboard. Hit its return to home function, and it would orbit the home position, giving you time to put on your goggles after your launch.
this particular one required you to manually set the position where you stood at the time ... it'll store this position for life until its reset to the next position. This isn't an issue unless you are flying out of a different location and space off the reset. At least you'll know where to look for it after you realize your mistake.
As is more often the case lately, GPS autopilots and flight controllers automatically set the home point to where they were powered up. (Why in the name of Krom did they not do this in the first place)

The industry has already developed a huge amount of the pieces needed for advanced UAV operation. We even have On Screen Display (OSD) telemetry, which gives us full instrumentation up to IFR requirements. By reverting to Nitro or gas power to regain run time. all that is really left to further develop is RF range related solutions.

I think, in terms of a goal. Further development of the relay tower to use satellite communication for control and vid would give us global potential, leaving only mechanical engineering issues to solve. Make a gas tank fly while maintaining battery charge.

 

[hevans1944]

The industry has already developed a huge amount of the pieces needed for advanced UAV operation. We even have On Screen Display (OSD) telemetry, which gives us full instrumentation up to IFR requirements. By reverting to Nitro or gas power to regain run time. all that is really left to further develop is RF range related solutions. ...

Well, there is still the subject of autonomous, or AI (artificial-intelligence) mediated flight. Not sure the hobbyist community is ready for that, but it is on the event horizon, appearing in a drone near you sooner rather than later. The future is beginning to look a bit grim if we human beings continue to develop replacements for ourselves...

... I think, in terms of a goal. Further development of the relay tower to use satellite communication for control and vid would give us global potential, leaving only mechanical engineering issues to solve. Make a gas tank fly while maintaining battery charge.

Really long duration, human piloted, electrically-powered flight has already been demonstrated by a three-day flight across the Pacific from Hawaii to Moffet Field, CA, but this was more in the nature of a publicity stunt. The aircraft had a single pilot and no passengers, but it was solar-powered... more than 17,000 solar cells re-charged the on-board batteries. Significantly, the Solar Impulse 2 landed at night. NASA seems to think an electrical-powered aircraft is possible. And, just to be historically accurate, back in the late 1960s I worked with a technician who was involved with Project NERVA, a nuclear reactor-propelled rocket system based on heating hydrogen gas to high temperatures and pressures and using the resulting thrust to launch a rocket into space. NERVA was cancelled without ever flying anything, but the proof-of-concept was valid.

So, making a gas tank fly is not much of a problem in this century. But you do need high altitude, above 50,000 feet, to make it practical. At that altitude you can also seriously consider solar power. Satellite data links would also be quite practical, albeit a bit pricey for amateur pilots. Hams have launched and used a huge number of "repeater" satellites, but these are in low earth orbit (LEO) and no one "bird" remains in sight for very long. Satellites in earth-synchronous orbit are plentiful, and therefore persistently visible, but I would imagine their bandwidth is fully booked by the commercial firms that paid to put them up there. Still, there might be some spectrum available for amateur (civilian) use. It's a path certainly worth investigating.

I don't think there are very many mechanical engineering problems left to solve for extended flight. Sure, the Global Hawk went waaay over budget, and its reliability was seriously questioned, and it costs a fortune to maintain and fly it... but it does still exist, it does still fly, and (from what I have heard) it does still take excellent pictures, tasked in real-time, at a fraction the cost of satellite overhead imaging. But, like Francis Gary Powers and the U-2, the Global Hawk in flight also becomes a target for anyone who doesn't care to be photographed from above. I am pretty sure that if thousands of hobbyists take up global flight missions, someone, somewhere, is gonna wanna bring 'em down. I would not, for example, attempt to take an aerial tour of the Great Wall of China from any altitude less than, say, 200,000 feet. Or an overhead shot of the White House either, for that matter, even if the drone is controlled from a nation-state without an extradition treaty with the USA.

Okay, so only one of us (and it sure ain't me) has any pilot creds for extended distance RC flight... well, I think maybe @Bluejets (Jorgo?) has some... so clearly this thread isn't going anywhere until we get more participants with practical experience, pilot creds for UAV flight, and perhaps licensed amateur radio operators interested in the subject. So I will just sit back and watch to see what happens for awhile. Sometimes threads like this just die because they don't reach a "critical mass" of contributors, or maybe aren't controversial enough to spark an extended discussion... we'll see.