Wireless Network from a Helicopter

Don't understand why you want to reinvent the wheel, and why you specifically sabatoged the way that already works by saying you looked at something different/new that may/may not work.....

Been using a digital camera for years, and have a USB memory card reader on the laptop (to read the photos off the memory card and copy em to the laptop), and an 5220 card in the laptop, always on and with internet access (1X in areas that are 1X only but EVDO in areas that are EVDO active) to send email/files (or email with files attached) to pretty much any internet address. Even used the same thing with a Sat phone to xmit pictures/email/voice from way out the way places that don't have anything (oil rig in northern Alaska, sailboat in the middle of the pacific, etc).

Someone else was asking about asking about live video from a RC boat.. We have succesfully used an x10 wireless spy video camera (transmits on channel

61), and a usb TV receiver on a laptop (receives the sig on channel 61, displays it/stores it on the laptop, and also xmits it over a datacard to other locations). The camera watches an area outside, and sends the video feed to a monitoring office (when someone is doing maint/repair, they can see it on the local screen). Works in factories/racecars/planes/regular boats/motorcycles etc, don't see why it wouldn't work from an RC boat too. The video camera and transmitter are extremely litewieght (about 3 oz's)

The information on the accessory you are talking about is pretty sparce, even on the canon website, it does say that it has a cable and an antenna, check with canon first, then take a look at the site below for the omni antennas,

The omni antenna can weigh as little as a few pounds

I don't know if the turbulence of the helicopter would negate the use of a magnetic mount antenna but the link above has all sorts of omni antennas including mag mounts.

as to a router or repeater, I don't know if the Canon WiFi transmiter would act as a bridge or what, but if you can set their wifi radio in the ad-hoc mode and the laptop on the ground in the same mode the radios would talk to each other just as two laptops would in an office inviornment.

As to the power needed, i can only assume that the camera would be self contained with it's own battery power. You could also use a small inverter for 12v-110vac operation. a 120watt inverter would draw approximately 10amps at 12 volts.

Bob Smith Robert Smith Consulting "Wireless Installations -- Government, Businesses & ISP's" F.C.C. Licensed-Commercial & Amateur Services A.R.S NA6T ARRL Life Member

1-707-964-4931 w/answering machine Fort Bragg, California 95437

"On The Air-Conditioned Mendocino Coast, In REAL Northern California" No trees were destroyed in the sending of this message. However, a large number of electrons were terribly inconvenienced.

Anybody interested in helping me brainstorm a flying wireless network?

What I need to do is be able to take pictures with a Canon 20D and use their wireless adapter to offload the images from the camera and somehow get them down to a laptop on the ground. My first thought was to have a wireless laptop on board to accept the images from the camera (which probably could be done just as easily with a wired setup between camera and laptop of some kind), then somehow have a wireless connection from the laptop in the helicopter down to a laptop in a truck on the ground.

We never take pictures any higher than 2000 feet above the ground, and we're typically within about 1/2 a mile of the photo site. So probably the longest straight-line distance the data would need to travel is approximately 3,300 feet.

I've researched several different options. I first looked into 802.11g with a hi-gain antenna on both the helicopter and on the truck. That seems to be the simplest option, I'm just concerned about what kind of range I can really expect.

I've also researched the Wi-Max system, but I don't think any hardware has been made available yet. It sounds like a great alternative, I just don't know how much something like that would cost, how much the equipment weighs, what kind of power source it would require, and how difficult it would be to setup. Please advise me if you know about it.

I've even looked into EVDO technology through Verizon, I was thinking of getting EVDO cards for both laptops and just ftping the files from one to another, my concern about that is the laptop on the ground may be able to download them quickly, but what about upload speeds? It's gotta be fast on both sides, right?

Please help, all opinions or suggestions would be appreciated. Thanks.

Adam

A few ounces, not pounds.

There is no way a mag mount would be suitable for a helicopter.

There are two significant things about antennas which will have to be considered. One is the directional characteristics of an "omni-directional" antenna. The other is polarization.

All of the antennas described as "omni-directional" only meet that specification for azimuth when they are vertically oriented.

In every case the "gain" (listed in dBi, or gain over an isotropic antenna) is the result of directional characteristics in elevation. Which is to say, the antenna radiates equally 360 degrees *perpendicular* to the antenna. However, as the angle of elevation changes from 90 degrees to 0 (the antenna is pointing directly at the distant end) the signal goes from having "gain" to having "loss".

If you mount an antenna pointing straight down from a helicopter the antenna will have significant reduction in signal strength at a receiver located directly beneath the aircraft compared to if the antenna is mounted parallel to the ground.

But, if you mount the antenna parallel to the ground, then polarization becomes significant too. The antenna on the ground must then be in a horizontal plane rather than vertical, and if the ground based antenna is pointing north then maximum signal happens when the helicopter antenna is pointing either north or south... and minimum signal happens the helicopter is pointing east and west.

Which is all to say, antenna orientation is necessarily going to be a problem.

One solution is to have two antennas mounted perpendicular to each other. Then either have two radios, or use a splitter to feed them both from the same radio. (A slitter necessarily causes a 3 dB lower signal, because each antenna gets half the power.)

Perhaps the best arrangement is to have dual antennas both on the ground and on the helicopter, but I suspect that in practice it would be sufficient to have dual antennas on the ground and mount only one on the aircraft. That will be true if the antenna does not have enough gain to make the "vertical beam width" too narrow. In this instance you get *nothing* from a "high gain" antenna!

I had someone take aerial photos of my property from a blimp. The blimp was about 15 feet long, and had a video camera and still camera. The two were fixed to the same gyro controlled table. The pilot was on the ground, with control of the blimp and the table. He would view something on the video, and then snap a picture with the camera.

In this case, it was tethered with 500 feet of cable, but wireless could do the same thing.

We don't know what the need is for the real-time delivery of the photos in the original post. A webcam might be the proper thing. It is live video with a still frame capability, downloaded to a PC automatically, which could be on a shared folder for WiFi retrieval in near-real-time.

A WiFi camera could provide real time to the ground, with still selection captured there.

I don't think I was clear enough on what my intentions were with the pictures. That detail is probably pretty important in order to find the right wireless solution. The intent is to take high-resolution pictures (roughly 8.5 megapixels) and attempt to sell them to either residential or commercial properties. The motivation for an instant wireless transfer is to have the ability to display the picture within seconds of actually taking it, and being able to take another shot at another angle if desired, without having to land to review the images.

Canon has introduced a new wireless file transmitter accessory to their high-end Digital SLR Cameras. This is what I'm intending on using rather than pulling the memory card out of the camera and loading the files into a separate laptop. Below is a quote from the press release introducing this new peripheral.

"New for the EOS-1Ds Mark II camera (also available for the EOS-1D Mark II and EOS 20D via a firmware upgrade) is the optional Wireless File Transmitter (WFT-E1A). Given the enormous popularity of LAN-based image transmission systems and the demands for higher speed image distribution in the reporting fields, Canon developed this new accessory that allows photographers to transmit images from their cameras directly to a computer over a wired or wireless local area network (LAN). The WFT-E1 transmitter includes a mini antenna, a long and short IEE1394 cable, a case and camera mounting screw."

I like the idea mentioned in another post about using an OMNI antenna on the bottom of the helicopter and another broad 180 degree antenna on the ground, but what type of router or repeater would I use?

Can anybody tell me how much the Omni antenna weighs? What about power? I can hook up a 12-volt inverter in the helicopter to power it, assuming it's a 110-volt system, but how much power can I expect it to pull?

I appreciate all of your time and comments on the matter. Thanks again. Looking forward to all of your comments and criticisms.

Actually there is one significant thing about Helicopters......

They have Non Ferrous metal skins (usually aluminum or fiberglas) Same problem with planes... Magnets don't stick.

What about a panel 'gain' antenna mounted on the bottom of the helicopter pointing at the ground and another one on the truck pointing up? Yeah, you're going to have polarization losses, but as long as you keep your gain down you shouldn't have any beam issues...

Two of them, oriented 90 degrees to each other and fed with a splitter, because polarization nulls are at least as significant as nulls in the beam.

Microwave systems are often designed with two entirely different signals, at the same frequency, on the same antenna using feed antennas with 90 degree polarization orientation to separate the signals. The "cross-polarization" difference can easily be maintained at 30 dB.

So if you have a healthy -70 dBm signal and the helicopter turns

90 degrees, it might then be a -100 dBm signal... which means it just isn't there.

Panel antennas may be the best choice for structural integrity on the helicopter too, and it might be possible to rig up a removable system that is strapped across the bottom of the aircraft with regular nylon webbing.

Even if a steel plate were attached, just to use as a detachable mounting base... helicopters do cruise at something over 100 mph, and I've never seen a mag mounted antenna that would hold in that kind of wind.

Been there, done that on a bigger scale. Some of the problems encountered were:

1. Nasty vibration from the rotors crossing over the tail caused the pictures to be fuzzy even at 1/1000 sec.
2. Autofocus didn't work in the haze.
3. Grad student in charge of holding a cast aluminium 24dBi dish antenna had trouble aiming the antenna at long range. A counter balance on a heavy duty camera tripod was a big help, but accurate aiming still difficult. The result was some fairly lengthy dropouts that required tweaking the TCP/IP stack timing to prevent disconnects and aborted downloads.
4. The antenna design was a mess. An 8dBi panel antenna did not have enough side gain (at 90 degrees) to work as the bird approached the horizon. They would lose the signal at about 1 mile when near the ground, but work to 2 miles if it was at perhaps 500ft altitude. An

8dbi omni antenna (bent brass rod collinear) worked much better going to perhaps 4 miles near the horizon, but would crap out directly overhead. The best results were obtained using a diversity bridge radio, with two dish tracking antennas spaced about 50ft apart run by two grad students. I designed and half built an electronic dish tracker, but grad students were deemed cheaper and allegedly more reliable.

1. Interference over populated areas was a serious problem. They would lose control erratically when tested over the city, but it would work just fine in the middle of nowhere.
2. The pilot noted that his simulator didn't function the same way as the real overloaded model helicopter and was having control problems. The helicopter cost 00 so much simulator practice is recommended. Tower Hobbies has useable small kits for 0-0. Free flying model simulator:
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The final compromise was to install a huge CF card and a timer on the camera. The camera would take pictures very 30 seconds or so. They would hover over the area of interest, shoot as many photos as possible, look at the results, and try again if they weren't good enough.

Incidentally, here is a web page full of high res photos of the California coastline.

these were taken from a full size helicopter and not a model. Might give you some ideas.

Chuckle. There's nothing ferrous on a real or model airplane to attach a mag mount. It's either aluminum, plastic, fiberglass, or titanium, none of which are magentic.

Directional characteristics (pattern) is important. However, it's a fair assumption that unlike an aerobatic fixed wing airplane, the egg beater will remain vertical and upright. Therefore, a vertically polarized antenna will work for every position except directly overhead. In that case, the radios are sufficiently close together that polarization will not be an issue.

Which is all that's necessary. Another advantage is that aerodynamic drag is not much of an issue with a helicopter. The antenna I threw together was just a chunk of RG-188a/u (thin TFE 50ohms), and piece of brass welding rod bent into a vertical collinear. The antenna just dangled under the helicopter and was not attached to the body (they wouldn't let me drill a hole anyway). It remained fairly vertical and got out of the way when it landed.

Yep. That's exactly what happened. However, the radios are sufficiently close together when directly overhead that it won't be much of a problem. We did see some dropouts, so I just bent the end

1/4 wave part of the antenna at a right angle, which mangled the pattern sufficiently to leak enough RF to prevent the dropout.

Nope. That's true if it were a surface mounted panel/patch antenna. However a dangling vertical omni maintains vertical polarization at all times. The model even has a piezo gyro to make sure it stays upright (which is really nice as it greatly simplifies control). Maybe you're thinking of GPS antennas, which must be circularly polarized to deal with changes in satellite orientation and Faraday rotation.

Oh, it's actually worse than that! Even a steel plate is placed at some convenient location to provide a "detachable" antenna mount... there is no way it will stay put when the chopper starts flying around.

I'm assuming that one possible scenario is that much of the work will in fact be close enough to "directly overhead" to cause significant problems. But that assumption of course may not be true. The point is, there is a *big* hole in the pattern, and for many types of vertically polarized gain antennas that hole is going to be large. If that is the type of work expected, that is the *wrong* antenna design.

Of course, it is also true, as you say, that that hole only comes into play when the radios are closest together. Hence if long range is important, it might well be a very good trade off to lose a bit of in close capability.

That's the point though... it depends on what they want to do, and it is in no way just a simple case of attach an "omni-directional" antenna to the bottom of the chopper and go with it.

Depends. If the images are going to be taken close to the ground (or from a model aircraft) that will certainly be true. But if the aircraft has significant altitude the images could also be taken when it has significant speed, and aerodynamics then comes into play during use. Otherwise, all that makes a difference is that it doesn't get blown off during higher speed runs between locations. Helicopters don't necessarily fly around at 20 mph airspeeds all the time just because they can...

As a side note, maybe 30 years ago I volunteered to help with a little project that involved hitching some equipment to the bottom of a hovering chopper, and before we did it the pilot went into a *detailed* description of potential problems and what I should do, mostly in relation to location, if anything went wrong. He wanted to *know* where I was going to be, and for me to *know* were that chopper would hit the ground if it crashed. I was not unimpressed with the detail, and commented on it. The pilot said: "In fixed wing aircraft a lot of mistakes result in /incident/ reports, and a few accidents. With helicopters there are *no* /incidents/, they are *all* /accidents/. That was one of the better pilots I've flown with, BTW.

(Did I mention that flying and aircraft don't bother me at all, but I am *scare shitless* of pilots!)

And made it equally bad at some other angle, which will cause dropouts at some distant range... :-)

Nope, I specified that as what happens if the antenna is mounted so that it has horizontal polarization (i.e., it does not apply to a "dangling vertical omni").

A circularly polarized antenna at the ground station would be one way to handle the changes in polarization of a horizontally mounted antenna.

Of course, again, this applies to an aircraft that is relatively directly overhead, as opposed to even so much as 1/2 a mile away. If the aircraft is going to range out at any distance at all, and particularly a low altitude, then an entirely different design model has to be used.

But *that* was my point, not the specifics of any one model. The fact that it depends on details that haven't been described means that specific solutions are all just jumping to conclusions, and should be avoided.

Argh. One of these days, I'll read the posting twice before replying. OK, full size helicopter, not a model. No problem.

CDF was using 2.4GHz to deliver video and data from IR fire cameras. You can buy commerical systems that do that:

$21,000. Oh cool, they also have a model system only $5,000-$7,000. A bargain. Here's their tracking antenna system: guess it would be fairly easy to have a GPS and altimiter calculate where to point a highly directional antenna.

Here's another one:

Just do a google search for "helicopter tracking antenna".

Anyways, everything I said about model helicopter antennas should also apply to full size helicopter antennas.

As for the FAA, it it isn't TSO approved, it can't be attached to the aircraft, but can be carried or temporarily attached. The perpetrators of the California Coastline photo project were good enough to show the helicopter and give a talk at our radio club meeting.

was also using ATV (amateur TV) and packet radio during floods we had about 4 years ago, to provide video coverage of the Salinas river trying to break through the levees. During that talk, he discussed the FAA rules regarding such equipment, which prevented use of a more efficient antenna system. Anyway, at the power levels and high frequencies involved, I don't think it's a problem.

Diversion: Here's a page on an RC model helicopter with a TV camera.

Well there are quite a few things wrong here. Basically i'm not sure of

802.11 technology has been approved by the FAA for use in the air. You see, they are very concerned with any type of wireless SENDING devices due to interference with onboard equipment. You might be hard pressed to find a pilot that will be willing to let you use any type of radio sending device onboard.

This might even be illegal. Something to check into. I've been a pilot for 4 years so this struck me as your first obstacle right away.

Now.. let's asume you can do this safely/legally. I'm guessing you would have to have to find yourself a powerful outdoor access point with a high range and external antenna. I know they make outdoor unit capable of 10-15km ranges. When you are 2000ft AGL you would probably have NO problem with ground interference. (Unless this is in the mountains). Basically the higher you go, the larger your range. I'm sure you could easily get 15-20km range out of a proper access point. This is the concept behind nav aids. VOR stations send of a signal that is good for about 2km on land... But when your at 39,000 ft you can pick up the signal for a range of 500km...

Good luck. Let us know how it works if you do it. It would be interesting.

--

802 Networks -- Think Wireless.

hi, pretty interesting discussion there. i just was wondereing if anyone is aware that the UAVs(unmanned aerial vehicles) the the armies of the world use (primiarily the searcher & heron family) use WiFi as the data link from vehicle to ground station. I have seen the RFLinx site which shows that they have military grade amps and radios for Wifi. Also the problem of polarization can be offset by using dual-diversity radio-antenna combos. ie one antenna at vert and the other at hor. there are multi-polarized antennae avl from ppl like wifi-plus but anybody's guess as to whether they actually work.

regarding the camera, wouldnt it be a good idea to use a speed-dome kinda camera or even the IPIX 360 degree cameras? these cameras have a network interface (wired or wireless) and also have Pan,Tilt & Zoom (PTZ) control. I personally know of ACti which makes a camera with 24x optical zoom which is sufficient for a lot of applications.

Jeff Liebermann wrote:

antenna on the

replying.

hi, pretty interesting discussion there. i just was wondering if anyone is aware that the UAVs(unmanned aerial vehicles) the the armies of the world use (primiarily the searcher & heron family) use WiFi as the data link from vehicle to ground station. I have seen the RFLinx site which shows that they have military grade amps and radios for Wifi. Also the problem of polarization can be offset by using dual-diversity radio-antenna combos. ie one antenna at vert and the other at hor. there are multi-polarized antennae avl from ppl like wifi-plus but anybody's guess as to whether they actually work.

regarding the camera, wouldnt it be a good idea to use a speed-dome kinda camera or even the IPIX 360 degree cameras? these cameras have a network interface (wired or wireless) and also have Pan,Tilt & Zoom (PTZ) control. I personally know of ACti which makes a camera with 24x optical zoom which is sufficient for a lot of applications.

Jeff Liebermann wrote:

antenna on the

replying.

I'm not familiar with that, at all. Interesting.

That is a very common, and very well understood, principle, which is exactly why I mentioned it previously. The problem, however, is that dual-diversity generally requires some type of a "combiner" or "switch" which is custom designed, and optimized, for some given application. And I just don't know of one that is readily available and also matches the proposed use that we've been discussing.

Note that a some wifi equipment, e.g., the LinkSys WRT54G, does use dual diversity with separate antennas. But I don't know that it would work well for a mobile unit, as opposed to a portable unit.

The WRT54G won't switch smoothly for a unit in motion, but works well for something like a laptop that is moved from one location to another. The problem is that the transmit antenna is selected according to which receive antenna last provided the best signal for a packet. That can result in a lot of packet loss for a unit in motion, where the last received packet may not be a good indication of the best antenna for the next transmission.l

With stock firmware, that's a problem, because it cannot be changed. But 3rd party software is available which might well make it work... by locking on one transmit antenna and then letting the receiver switch by whatever (unknown) algorithm it uses. It might be interesting to try, as receive diversity using (two) antennas with space diversity and/or polarization diversity is very commonly used, (and generally space diversity is implemented with a single transmit antenna).

What I suggested earlier, using one unit with two antennas and an RF splitter, is not nearly an optimal way to go! It is, however, the least expensive and easiest to experiment with.

Why not cable from the camera to the laptop and check the photos as you take them with a laptop? The Canon

USB 2.0, so what you need is a large-display laptop, all of which nowadays support USB 2.0. You would have to have a laptop of some size, anyway, to pick the files from the Canon and push them into a WiFi card, so why do you need to send the files by WiFi, which will take forever to send a hi res image at that distance?

If you absolutely, positively, have to look at the images on the ground, then make sure to install the antenna on the whirlybird for *horizontal* polarization, and likewise for the rectenna on the ground. Mismatched polarization can result in an 18db loss you really don't want.

Gain requires aim... are you going to have someone on the ground tracking the whirlybird? If not, you degrade your system somewhat, as very high gain antennas are very, very directional. There's not a ghost of a chance of steering the airborne antenna, anyway, as that would drive the complexity and therefore cost of this to near-military costs, so you can't have a highly directional high-gain antenna aloft at any reasonable cost.

There's pre-standard gear out there. However, it's spendy, and you had best count on amortizing it over a year, as when the standard is set, your manufacturer may not be able to fix the firmware to make the pre-standard gear match the standard.

Would work, as would EDGE from Cingular.1xRTT from SprintPCS would be slower. BTW, EDGE can work outside of North America, if your data card supports overseas frequencies; EV-DO and 1xRTT are limited to North America, and a few odd places here and there. If you don't travel, no problem, but if you go to Yurp, go EDGE.

External antennas are available for most cellular data cards. Most services are designed to cover the ground, not the air, so borrow a card from your carrier of choice and take it up to see what the signal's like at your preferred altitude.

IANAL, but I believe there may be an FCC restriction on the use of 800MHz services (e.g., Verizon) while airborne. 'PCS', or 1900MHz services, are not so restricted. I'd peruse the relevant FCC regulations before adopting a cellular solution. You could start at

go on from there.

The FAA requires the pilot to approve the use of radio devices while in flight, so as long as your pilot's OK with whatever you do and it does not interfere with systems on other aircraft, it's OK with the FAA, IIRC.

EV-DO, EDGE and 1xRTT are symettrical when it comes to speed. Yes, fast is better.