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[ptichkin]

What frequency can be used in US to send low bandwidth information (like spacial orientation, altitude, may be GPS) from an aircraft back to the ground ? Will it be just another channel in 72MHz range ? And what kind of tx/rx equipment would normally be used ?

Mainly, I am looking for ways to get an aircraft to high altitude (up to the legal limit of 1500 feet) for good air photography,and the main issue seems to be visibility - it is hard to see and control a parkflier beyond 300-400 feet.

[clolson]

I'm sure others will chip in with better advice, but there are some 900Mhz and 2.4Ghz radio modems out there that may do what you need. Imagine a long serial cable (but wireless in between.) You could use something like this to connect a gps (on your airplane) to some moving map software on the ground. And it's a generic serial connection so if you can code software on either end, you can do just about anything you want.

I've used a 900Mhz Aerocomm unit and we got about 1.5 mile range (before the first dropout) with the standard omni-directional antenna. These are a bit big/heavy for a park flyer though.

Maxstream makes something of similar size/capability.

The aerocomm's are about $225 for a pair. Maxstream is closer to $400 for a pair, so they aren't exactly cheap.

That's as far as my investigation has taken me, so I'd be interested to hear what other products are out there that can also do the job.

[enae100]

Not to sound completely lazy...but can you (clolson) provide a website(s)?

[typicalaimster]

The aerocomm's are about $225 for a pair. Maxstream is closer to $400 for a pair, so they aren't exactly cheap.


Hmm was this the 1 watt Maxstreams?

[clolson]

I haven't looked real close at the maxstream specs, could be 1 watt. I don't have links off the top of my head. I'd have to google for them. I think mouser.com sells the aerocomm, I forget who sells the maxstream ... maybe maxtream.com???

[typicalaimster]

I forget who sells the maxstream ... maybe maxtream.com???

http://www.maxstream.net/

I have a pair of the Xtends that I picked up when they were $200 for the dev kit. They've worked pretty well in my RC Car. I haven't taken them up yet! That's why I was wondering if it was the 1 watt version of the lesser 100mw version.

[typicalaimster]

Funny how I just received an email from them...

9XStream 900 MHz 100 mW Development Kit

$249 per kit (normally $409 per kit)*

MaxStream’s 9XStream Development Kit includes everything you need to easily test the range and functionality of the versatile 9XStream modules. Simple connections via RS-232/485 interface boards and advanced networking software allow for a quick configuration of your wireless network.

[clolson]

My turn to be lazy ... maxstream has a lot of different products and varients. Do you have a link to specifically what they are selling with this deal? Does it include 2 ends for that price?

Thanks,

Curt.

[clolson]

Oh, one more thing. I forget if I posted this here, but related to this topic ...

If you plug any standard handheld GPS into a radio modem onboard your aircraft, and capture the live data stream on a ground station (i.e. a laptop plugged into the other end of the radio modem link) then you can replay that data with FlightGear (www.flightgear.org). Disclaimer: this functionality has only been recently added to the source so you need the development tree and need to compile yourself.

But if you go through that agony, the result is that you can replay your entire real flight inside FlightGear with synthetic scenery, virtual 3d aircraft, virtual 3d instrument panel (that is animated and working) including cockpit view, chase views, tower view, etc.

I live in MN so the FlightGear scenery for my club field is really boring, but you can see some sample screen shots here:

http://www.flightgear.org/~curt/Models/Special/Rascal110/

It's relatively simple/easy plug-n-play instrumentation/telemetry, but you can get a lot of mileage out of it. In the virtual cockpit view, pretty much all the instruments are live and working ... attitude indicator, altimeter, airspeed, rate of climb, directional gyro, even the virtual HUD. FlightGear has a virtual model of all the VOR/ADF/ILS stations so you can even tune in local navigational aids while your replay is playing and see the needles respond accordingly.

Down the road I plan to rig things up so I can feed in live data (and smoothly interpolate 60hz from the 1 or 0.5hz gps data.) This would make a neat addition to any ground station ... especially if you added restricted airspace and other interesting information to the virtual view. It might even be possible to fly 100% off the virtual view if you are careful, or if your aircraft has good stability. Not that I'm advocating that sort of thing of course ...

FlightGear is open-source and pretty flexible so with a little hackery you could do fun things like flash a warning when ever you get close to or over 400' agl. FlightGear has an accurate terrain model (SRTM based) for the entire world, so you could send up a ground elevation estimate to your UAV periodically if you are flying in areas with changing terrain,. There was even a project where someone superimposed their live video feed from the airplane on top of the synthetic flightgear view. FlightGear supports multiple visual channels so a pilot could be sitting inside a cockpit with an immersive synthetic view surrounding the live video feed.

There are lots of fun things you could do combining FlightGear and UAV's. FlightGear is 100% volunteer driven software, so if any of this tickles your fancy and you want to pitch in to add new interesting features, feel free to contact me offline.

Curt.

[ptichkin]

Thanks for your suggestions. What about spacial orientation ? Is there a standard unit that can transmit plane's angles relative to a horizontal plane, and vertical axis ? If not, then how one can fly an RC plane beyond ~400 ft range ?

[typicalaimster]

Do you have a link to specifically what they are selling with this deal? Does it include 2 ends for that price?


You get two units which will complete a downlink..

http://www.maxstream.net/products/xstream/devkit/9xstream.php

That's the 900 mhz one. I have tested the distance over flat land up to a 1/4 mile. That was at 4800 baud. My GPS only goes at 4800 baud so it works out.

--Scott

[MaxStreamInc]

We are selling 9XStream Development Kits for $249 this month (regularly $409). These 100 mW radios have a range of up to 7 miles with the included dipole antenna (line-of-sight). Check out the website at http://www.maxstream.net/web-special/ and take advantage of this sale which runs until the end of August 2005.

[kd7ost]

oops, posted in the wrong thread. can't remove.

dan

[Lost In OC]

I would like to see a thread showing how to set up the maxstream system from start to flying. Sort of a dummies guide. Might help sell some units.

[danstrider]

I'm getting my hands on the Microhard 920MHx units, will report back how easy they are to use/setup. Looking forward to the change from a slow Aerocomm setup...

Dan

[Lost In OC]

I'll stay tuned!!!

[vpatron]

Hi guys,

The cheapest effective way is to use a system for ham radio called APRS - Automatic Position Reporting System. It can be adapted for any frequency.

All you need is a simple microcontroller to create 1200 baud FSK modulated audio tone. An easy task if you know your stuff or buy a module for $59. Then feed the audio into one of those wireless video transmitters (e.g. Black Widow, cheapo Ebay ones, or whatever).

At the video receiver, you feed its audio out into your laptops line in and run a software modem program available cheap or free for APRS. I believe it creates a virtual serial port that most GPS software or your software can use.

Voila, you have a cheap and effective data downlink.

Anyway, that's my plan for my UAV, but I'm still 6 months away from needing this part of it.

A Tucson, AZ ham radio club has a lot of gear and info on APRS. Just Google for it (takes too long on my cell phone).

Regards,

-Vince

[sesat]

I second Vince's suggestion. See how Paparazzi impements it inexpensively. Such a marginal cost if you already have a 2.4GHz video downlink.


Ram.