[Paparazzi-devel] Re: Does the modem interfere with 2G4 radios?

[Martin P]

Hello,

yesterday I did some ground testing on the RC flying field. I am the only one 
who uses an autopilot. I had warned the other pilots that I use 2G4, just in 
case. One guy who was flying a Funjet suddenly shouted that his plane doesn't 
react any more, so I quickly disconnected the power supply of my aircraft and 
the USB cable of the ground statiion modem. Then he didn't have any more 
problems and was able to continue his flight. 

I am using 1mw Xbee ZB modems. He flew with Futaba FASST. 

He is not 100% positive that actually there was an interference, it all went 
very quickly. He took off while my modems were powered on. My ground station 
was behind the safety fence (metal), the plane was parked on the actual flying 
field. To me it looks as if an interference occurred when his plane came in 
unobstructed line of sight to my ground station. It has been in unobstructed 
line of sight to my to my plane all the time. 

My ground station modem is configured as coordinator, the other one is 
configured as end device. In the plane I use a Nintendo antenna for the modem. 

What did you experience? 
Greetz, Martin 

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From:  chris 
Subject:  [Paparazzi-devel] Does the modem interfere with 2G4 radios? (Martin 
P) answer from Chris Efstathiou 
Date:  Sat, 07 Mar 2009 19:54:22 +0200 
User-agent:  Thunderbird 2.0.0.19 (X11/20090105) 

Hi.
I have recently equipped my Multiplex profi 4000 with the ACT S3D dual FHSS 
system http://www.acteurope.de/html/start_english.html
I only have one flight with it but a lot of ground testing and i am almost 
certain that there is no problem operating a FHSS system like the s3d or the 
Futaba FASST in close proximity with the Xbee 60 mw 2.4 ghz modem.
The separation of the s3d dual receiver and the Xbee modem is about 60 cm (~2 
feet) on my Multiplex EasyGlider and the range is not reduced at all during 
flight and during range checks.
After all operating both a Xbee 2.4 ghz modem and a FHSS system is like having 
two pilots flying two airplanes at the same time, one equipped with say a 
Spectrum or JR system and the other with a Futaba FAAST system, a rather usual 
situation.
Chris
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From:  Martin P 
Subject:  [Paparazzi-devel] Does the modem interfere with 2G4 radios? 
Date:  Sat, 07 Mar 2009 12:16:28 +0100 


Hi, everybody! 

I would like to know if anyone has experience with Paparazzi and 2G4 
transmission. I do not intend to fly Paparazzi with a 2,4GHz safety link, but 
as 2G4 becomes more and more popular, I would fly near other people who use 
2G4. I don't want to cause a crash. 

Theoretically, it should not be a problem as the 2G4 radio should hop to 
different channels and the interference should be very short. Unless the modem 
uses too much bandwidth. 

On the other hand, I would like to know if the modem works while a 2G4 radio is 
near. 

Greetings, Martin