Inexpensive options for long range video transmission???

[pikeater]

Hi guys, I'm looking for any feasible options for long range(15miles+) video transmission. The autopilot/comunications system has been taken care of however this link does not allow for enough data transmission to piggy-back the video on. Additionally I'd like to be able to transmit at least two seperate video feeds and keep the weight below 5lbs for the transmitter/power. I've looked around at some of the basic video transmitters but keep hoping there's some unique if unorthodox approach to this problem. I'd appreciate any ideas no matter how unconventional. Thank You.
Wyatt

[trashmanf]

my idea (although I haven't even attempted to implement it yet) is to set up a couple UAVs on preset timed flight paths, then you could have a few "hops" to get to your ground station. I.E. you launch your first UAV, as it becomes a mile away or so. launch your second one, then hopefully you can somehow keep them within range of eachother and you. Repeat as desired? :)

[pikeater]

Sound's interesting. Each plane would then relay for the plane ahead of it. Would each plane be controlled seperatly or would they all rely on the same transmisson? I had thought of leapfroging accross several ground stations but wasn't sure how you would relinquish control from one and pick it up on another.
Wyatt

[bearcreek]

If you want full video bandwidth (~5mhz) you might be able receive from that distance with highly directional antennas like a satellite dish, but if you can decrease the bandwidth using a lower frame rate/resolution or digital compression then you can increase efficiency.

With one microcontroller you can build a buffer for an ntsc camera down to 320x240 resolution at 1 fps with only 20 khz bandwidth, which is about 200x higher bandwidth efficiency or 15 times greater line of sight coverage range for a narrower band receiver - and possibly low enough to feed through a cellular phone or amateur handheld tranceiver with a little tweaking.

[trashmanf]

I wasn't thinking of "controlling" the repeater planes exactly, more like just planning out your flight so that you could set their waypoints on a GPS and have them in the approximate area you would need. A directional antenna would be cool, but make sure you stay in the beam!

[Tom in Cincy]

I was into Ham TV (ATV) for many years. Low power (under a watt or so) could carry for 20-30 miles Line of site. Here is a simple calculator http://www.qsl.net/kd4sai/distance.html that may aid in giving you an idea of how far you can fly away and still have the plane see the control site.
There are high gain antennas called loop yagi's that worked well at these frequency and were very manageable in size for the ground station. model # 1221LYRM for example. http://www.directivesystems.com/

I realize this may not be of any value or relevance. Some of the stuff you guys are doing is very advanced. I have always had an interest in UAV and have toyed with it a little.
Good luck
Tom

[Medve]

well, how about having a slow, powered glider type, plane go up locally, like right over your flying sight, and act as a repeater for any signals. Essentially like an AWACS.
A local pilot would be flying this plane, while someone else used this "elevated antenna"
to control or receive signal from the UAV.

[pikeater]

Were planning on doing a 1.2ghz loop yagi antenna system on the ground with a simple 5/8 wave dipole in the wing of the aircraft driven by a 200mw camera transimtter with a 2 watt linear amplifier but were still not sure what kind of range to expect. Can anyone see any problems/ improvments for this setup?
Thanks
Wyatt

[kd7ost]

What country are you in? 1.2 Ghz is not legal in the US even though you can buy some equipment in that frequency range. It is used in commercial aviation at that frequency or close to it for some type of communications. High gain antenna's and receivers with a high input sensitivity are better than cranking up transmitter power. LOS is also needed. Especially at Microwave frequencies like the higher power legal with license 2.4 ghz band. 900 Mhz needs bigger antenna's. The more directional, the better the gain. I would suggest an antenna and receiver as high off the ground as you can get it.

Google Monte Salot.
Inexpensive and Long range? Lotsa luck. ;)

Dan

[rclinks2002]

Arent the video cameras available from blackwidow av 1.2ghz? They dont require a license do they?

[kd7ost]

Arent the video cameras available from blackwidow av 1.2ghz? They dont require a license do they?

No, they're 2.4 Ghz. License. Hmmmm. This is the fun part. They operate at a power level that requires you to have at least a technician class Amateur radio license. I have one. My sign on name, kd7ost, is my call sign issued by the ARRL under FCC ruling. To use one legally, you need the license. It's easy to get and you can be proud of doing it. Most guys don't give a rats behind and just buy it and use it because it's not really policed at this time. The true test of character is what you do when no one is watching. ;)

Dan

[rclinks2002]

...

[pikeater]

Thanks for the heads up Dan. I certainly won't go with the 1.2ghz system if it's illegal. We do have an amatuer raido operator in our group so perhaps the 2.4ghz system is the way to go. It's really suprising that 1.2ghz systems are so proliffic here when they are, in fact, illegal. Thanks again.
Wyatt

[kd7ost]

While the topic came around to this I should post this again. It comes up every so often. Here is a website anyone can go to take the current test as a practice test. Once you can pass this test with regularity, you can take the official test and get a license. It would be good if everyone operated this way.

http://www.qrz.com/testing.html

Dan

[rclinks2002]

Dan,
Wouldn't the FCC (NTIA) have an issue using a UAV for commercial means? I assume that the UAV would be transmitting information back that could be used for profit....Such as reconnaissance on a contract basis? Thanks
Ben

[kd7ost]

Ben,

If you're using Amatuer radio, you cannot use it for profit. There's nothing wrong with using a UAV for commercial means though.

Dan

[rclinks2002]

Do you know of any systems that would be legal? I am afraid to use any of the transmitters off ebay since I have heard that they also carry over into the Ham bands.

Thanks
Ben

[kd7ost]

I've never researched commercial AV systems. Anyone else reading this know of systems and licensing requirements for AV equipment you can use for a business?

Dan

[Tom in Cincy]

Just a FYI. There is a 1.2 ghz band available for Amateur Television. It exists between 1240mhz and 1300mhz. I ran ATV there for years and it was great. Very little interference. There is also enough room to fit 2 video signals in . http://www.arrl.org/FandES/field/regulations/bandplan.html
Scroll down to 23 cm for exact frequencies. The exact allocations are (ie narrow band, eme ) are just ARRL recommendations. You may operate anywhere in the 1240-1300 on a limited (non interfering basis).
I believe the controversy over the cheap Pacific Rim mini transmitters was the fact that they transmitted outside the Amateur Radio frequencies. They drifted all over the place by many megahertz. And those frequencies above and below the ham band are allocated to the government (maybe FAA navigation?).
I don't believe any of the transmitters sold by BWV or anyone else is legal without a Amateur Radio license. No matter what the power output or frequency. The reason being the FCC also stipulated the device have a limited range of a few meters. So 1 milliwatt into a high gain antenna traveling hundreds of meters was just as bad as 100 watts into a dead short if it radiated the signal too far. (It use to be this way maybe not anymore).

Good luck with your project. Im jealous. I wish there was a group around Cincinnati that wanted to do such a project.

Thanks
73's
Tom WA8ZAH

[kd7ost]

Thanks for the info Tom. I'm not fully clear on the 1.2 Ghz stuff and was always told it's just not legal in the US. There may be more to it. Maybe like you said, there isn't a non-licensed 1.2 Ghz system.

Dan

[pikeater]

I guess I'm getting confused. It seems all systems require an amatuer radio liscense, which, by nature can, only be used for non-commerical purposes. How then does one use use a system in a UAV for commerical purposes?
Thanks,
Wyatt

[kd7ost]

There are commercial systems out there. We simply don't know of them because we aren't operating commercial ventures with video. You might ask at the Mr.RC-Cam forum. There are different schools of knowledge living there. ;)

http://www.rc-cam.com/forum/

Dan

[Tom in Cincy]

How then does one use use a system in a UAV for commercial purposes?

The answer is you buy a permit from the FCC. You will need Lots of $$$$$$.
Then add lots more $$$$$ for the equipment because Ebay or BWV is not going to cut it.

If I were you, I would develop the system using the existing consumer grade equipment available. If it works and has great merit sell it to the military as they can do pretty much what ever they like.

Probably not what you want to hear. But it is "All about the Money"

[rclinks2002]

What about taking the video, converting it into a rs232 signal, then putting it through a radio modem and transmitting it back to the ground where it will be converted back into a video signal????

[MX]

What about taking the video, converting it into a rs232 signal, then putting it through a radio modem and transmitting it back to the ground where it will be converted back into a video signal????

The RS232 radio modems don't have nearly enough bandwidth for video. Video needs about 5 MHz. The modems do about 115 KHz.

MX

[pikeater]

Thanks to Tom, Dan, and MX your info has been very helpful. The Mr.RC-Cam forum was also a great help. Does anyone know of any additional sources for info on commerical UAV use?
Wyatt

[kd7ost]

There's probably not a lot available for general consumption. As hobby UAV builders and drivers we're very open with what we do. Heck, I betcha small business UAV guys come here to read but don't post what they're doing. It's a new and highly competitive industry. Its future with impending FAA regulation isn't clear but it will be strict for anyone flying beyond visual range in an autonomous manner. In the future, legal video links will be the least of your concerns. Sense and avoid systems, transponders, commercial licensing etc, whatever it takes to get into the NAS will be tough and contentious.

I don't want to throw a wet blanket on your project but I can predict if you guys continue on, create a viable product, get it in use and are 10 years down the road, you will look back on this time and realize the plane and electronics was the easy part. The cost and certification will be tough. There's a lot to chew out there and the FAA regs aren't fully in stone. You might want to start with this recent FAA policy letter. http://www.uavforum.com/library/faa_uas_policy.pdf

I don't think you'll find a lot of "How to" information from competitive businesses.

Dan

[Quacker]

Here's a potential "out" as found in the policy document.

[kd7ost]

It depends on what you want to do. The AC they refer to was designed around RC aircraft. It specifies no flying over 400 feet agl. It also assumes only flying via RC system within visual range. It also assumes no commercial application. So what that statement says is that if you fly a model airplane and stay under 400 feet, you are exempt from the uAV policy. AMA doesn't even ask you stay under 400 feet unless you're within 3 miles of an airport. It doesn't help the UAV guys wanting to have their plane fly off on an autonomous mission.

Dan

[pikeater]

I appreciate the article, it definitley underscores some of the problems we'll be facing. I'm really surprised the wording of the article was as forgiving as it was, at least they recognized an immediate mandatory avoidance system would ground nearly all UAVs. Right now I'm primarily concerned with developing a system for amatuer, commerical, whatever use on wildfires just to get interest. Thanks again for the feedback,
Wyatt

[Iraqigeek]

If I may jump here a little. I used to setup wide area wireless networks based on WiFi (2.4GHz band @ 100mW) equipment. Since amplifiers were sooooooo expensive, we lived and died on high gain antennae.

What we used to do at the ISP site, or repeater towers was stick a 15db omni antenna at some 30 meters above ground and on clients sites, use a 4db patch panel (which was quite cheap) placed at the focal point of a 60-90cm offset parabolic antenna at the roof top. Using this setup, we were able to get about 5km range with high reliability (even with a lot of trees in the way).

Considering the altitude of the plane, I dont think it would be that hard to get 15 miles of range using a 1.2-1.5 meter dish, a good gain patch panel, and a few hundered milli watts of power on the plane. However, a parabolic dish is highly directional, and you would require a two axis motorized base to control the orientation and elevation angles of the dish based on GPS info of your plane recieved through telemetry.

[Quacker]

If the antenna relies on transmitted GPS data for orientation, doesn't that create a vulnerable system? If the transmission is interrupted, the antenna might never reacquire due to lack of GPS data.

Q

[Iraqigeek]

Didnt you say that you already have solved the telemetry comminications?

My suggestion was for the video feed only. I wouldnt think, even remotely, of using such an arrangement for telemetry. All mission critical communications should rely on omni directional antennae on both ends, or in the worst case, directional antennae (only for the ground station) that have wide angle coverage (over 90 degrees).

[pikeater]

Yes, I belive we have a viable solution for telemetry, communications, etc. it simply does not have a high enough transfer rate for video. The high gain/tracking concept is certainly interesting. Since the telemetry data should be very reliable, I assume that the dish wouldn't have too much difficulty reaquiring the video feed if it was interupted.
Wyatt

[Quacker]

Hi pikeater,

I see. Strike my earlier comment.

There is a low overhead way to get a tracking antenna to lock on a signal without GPS data. It involves moving the antenna in response to differential signal strength. It can be implemented as a hardware analog or a digital solution. The idea that it is not dependent on telemetry data could be beneficial to overall communication reliability. Let me know if you are interested in the details.

Best,
Q

[ehx]

Here's a paper with details along the lines of what you are talking about.

www.uav-applications.org/gallery/img/6.pdf

The problem is I doubt any ground-based receiving dish is going to work for you. You need line-of-sight and some simple trig shows that even if your UAV is a mile high when it is out around 15 miles horizontal distance it will be less than 5 degrees above the horizon. Short of doing this over water or always being able to setup your receiver on a mountain top you will rarely get a clear horizon down to a few degrees. If you expect your UAV to get down to a few hundred feet above ground there's almost no chance it will work.

[rclinks2002]

Is there anything you would reccomend for our system? Other than the use of Satellite uplinks? Thanks

[Quacker]

repeaters?

[pikeater]

The article was definitly along the same lines as what we're in the process of doing. Line of sight is clearly a problem esp. in an area with mountains or signifcant elevation issues. Repeaters might be an option but would require a significant hassle in terms of setup/power. I suppose an aerial repeater would be an option although that would probably make the directional tracking system for the video feed next to impossible. I'm hoping to do some tests in a fixed wing over the next couple of weeks and will try to let you know how things go. Thanks.
Wyatt

[Iraqigeek]

I doubt you could relay signal if there was a mountain in between without having a hop in between your plane and the ground station. However, vegetation shouldn't be a big problem. Sure vegetation degrades the signal, but still you could get a nice signal if the only thing blocking your LOF are trees.

Regarding the PDF above, while the concept was definately sound, I think the implementation was not so perfect. First, they could have used high gain omni directional antennae mounted in the wings, since they had such a large platform carrying the two bridges. Second, 21db dishes are nothing spectacular if you want such long range links. A 24db gparabolic grid is a very common and cheap solution, and is still much smaller than a 3 footer dish. Pair that 3 foot dish with a cheapo 4-6db panel, and you'd have a much higher gain (especially if using an offset dish). I cant give numbers as it depends on the gain of the dish you use, and there is a good deal of work involved in tuning the setup since it requires some modding to mount the panel and then tning the setup for the highest gain.

Another thing regarding long range. Before the war, we didnt have a cellular network in Iraq, and we used long range wireless phones as a substitute. I used to install such phones for a living back then. Many of those phones operated in the 878MHz band and with 5W on the handset (the base station usually has a 15-25W amp), many were able to reach a range 50KM (~30 miles) downtown and 80+KM in rural areas. I know the transmission power is very high, but you have to take into account that the handset has an antenna that is less than 50cm long (~1.5 feet, around 5db), while the base antenna, an 8-10db omni, would be monted about 24-30 meters (80-100ft) above the ground (depending on the hight of the building, the tower was usually 12-18 meters high).

Keep in mind that those were bi-directional links, so the cams mentioned in the PDF above, and the handsets in my example had to be able to recieve a very good signal with a rather small antenna. Also, in the PDF above, they were dealing with a digital signal, and from reading their numbers, they were operating at full theoretical speed (11mbps) which requires a signal over -80db. An analog video link is a lot more forgiving in terms of SNR and signal strength required to get a good picture.

[rclinks2002]

DO you think if we were able to compress the video (somehow) and then use this to transmit the video back?

http://www.aerocomm.com/rf_transceiver_modules/ac4790_mesh-ready_transceiver.htm

Sort of the IP webcam idea.....

Thanks
Ben

[Iraqigeek]

Even if you could compress the video to stream in under 76kbps (the rate at which the transciever operates) without loosing 90+% of the quality, the resulting stream will be very untolerant to transmission errors. To give an example, the good old MPEG standard (used to encode VCDs) can support only 1 bit of error (and a specific bit for that matter) in every 64 bits of the stream without distorting the 8 by 8 pixel window whose information is carried by this 64 bit block. If you managed to get such high compression ratios to get a stream that requires 76kbps or less, then a single bit of error will result in a much larger distortion to the frame to which this bit belongs. Dont even get me started at the amount of processing power you would require to compess that video stream in real time to such low bit rates.

I still believe that going analog is a lot easier than trying to tranmist a high bandwidth digital signal. An analog video signal is in orders of magintude more error tolerant than a digital video stream. In the precense of interference, or if the signal is weak, an analogue video feed will give you a grainy, yet still good picture. A digital feed operating under the same conditions will most likely give you a bunch of big, randomly coloured squares on your monitor (similar to playing a VCD full of scratches).