Simple Long-Ranged Audio Link for UAV - SparkFun Electronics Forum

Simple Long-Ranged Audio Link for UAV#35197

By Krogoth - Mon Sep 17, 2007 1:55 am

- Mon Sep 17, 2007 1:55 am #35197

I'm trying to develop a backup radio system for a UAV to compete in the Australian Outback UAV challenge (www.uavoutbackchallenge.com.au).

The UAV already has high-powered Wifi and two 1W Aerocomm RF modems, but I was thinking about adding a simple audio-based heartbeat-type transmission from the ground to the UAV - I've read about people using DTMF codes for this. The mission specifications say that the plane must automatically crash (:S) if it goes outside radio range, so I want a simple backup radio in case the higher-level stuff fails.

What I need is one of you ham radio guys to point me in the right direction. I'm trying to get by without getting myself a radio licence, so I have to stay below the 4W EIRP limit, but all I need is some documentation or a how-to on building a simple FM radio transmitter with around 1W of output on an unrestricted spectrum, and a receiver to match.

I'm an undergraduate mechatronics engineer and thus have a good knowledge of all things electronic, I'm just not sure where to start on a seemingly basic and common project.

Thanks in advance for any advice.

Will.

#35204

By RonnyM - Mon Sep 17, 2007 10:31 am

- Mon Sep 17, 2007 10:31 am #35204

Go to www.hamtronics.com. Theirs stuff is awesome, you can build from a kit, and it will work out of the box.I have built VHF and UHF transmitters and receivers of theirs, along with tone control circuitry for long range wireless video cameras. It saved a month of futzing, and the client was exceptionally pleased. Designing a rugged VHF system with the vibration and huge atmospheric swings the UAV will face, will be a huge undertaking but not impossible. You need to pick the battles...
Ron

#35207

By stevech - Mon Sep 17, 2007 12:34 pm

- Mon Sep 17, 2007 12:34 pm #35207

you DO have an FCC license for radios in those bands, right?

#35264

By wiml - Tue Sep 18, 2007 10:37 pm

- Tue Sep 18, 2007 10:37 pm #35264

He probably doesn't have any FCC licenses because he's in Australia.

#35272

By Krogoth - Wed Sep 19, 2007 5:46 am

- Wed Sep 19, 2007 5:46 am #35272

Correct, we're not regulated by the FCC here but by our Australian equivalent. I found out I can legally transmit unlicenced at 1W EIRP on the 900MHz band and 4W EIRP on the 2.4 or 5.8GHz bands, but they require frequency hopping and high-level comms which is precisely what I'm trying to avoid. Every other band has maximum power levels around the 4mW range. Looks like I'll have to get myself a ham licence, then...

#35280

By RonnyM - Wed Sep 19, 2007 8:09 am

- Wed Sep 19, 2007 8:09 am #35280

The US has a "MURS" (Multi use radio service) non liscensed band centered around 151 MHz. Max power is 2 watts for voice or data. Perhaps there is a "DAMB" (Dingo ate my baby) equivalent.

(Sorry, I couldn't resist that one)
Ron

#35307

By stevech - Wed Sep 19, 2007 12:35 pm

- Wed Sep 19, 2007 12:35 pm #35307

I'm testing a pair of MURS (US, FCC, 153MHz) modems. Half watt = low cost. There are 2W ones, but are pretty costly. raveontech.com

The Maxstream 900MHz PC board modems or boxed product version are good. Their 1W FHSS product has quite long range in line of sight, and more so with a yagii on one end. I have a pair of these. At 1W, they do blast into radios and cordless phones, and my PC's speakers!

I also have used $30 Maxstream XBeePro (60mW) at over a half mile line of sight. A high gain antenna on one end would extend that greatly.

Maxstream.net (now digi.com)

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