Replies to This Discussion

Permalink Reply by Overwatch on December 31, 2009 at 10:40am

GSM 900 has a bandwidth of 50 MHz: 890-915 MHz for upstream (mobile->tower) and 935-960 MHz for downstream (tower->mobile). The 868 MHz Xbee should operate in the 868-870 MHz range (otherwise they wouldn't sell it in Europe). So there's no overlap and there shoudn't be any interference from a healthy GSM cell tower.

The range should be up to 40 km LOS (or 16 km if in Italy).

(correct me if I'm wrong)

Anyway, what environment did you do the testing in? Did you have a clear line of sight? What antennas were you using?

• ▶ Reply

Permalink Reply by Varga András on December 31, 2009 at 10:40am

I think there's no interference between GSM and ISM 868 bands. In Hungary we use GSM cellphones and you can buy 868 MHz radio modules.
The datasheet says that 40 km is the outdoor, line-of-sight range of this radio. In urban conditions it's about half a kilometer.
My further question:
what about 868 MHz ZigBee + 1,3 GHz video downlink? (868*1,5=1300)

• ▶ Reply

AdminPermalink Reply by Morli on December 31, 2009 at 5:29pm

What about Aerocomm's :( , I have the US ver , ( i used the spectrum analyser software that comes with but did not see much of other signals though I have towers near by).
AC4790-1000
Frequency Band
(software-selectable)
902MHz - 928MHz (US)
915MHz - 928MHz (Australia)

• ▶ Reply

Permalink Reply by Alex on December 31, 2009 at 11:22pm

Thank you for your suggestion.

Actually the 1.3GHz video + 868 Xbee is also my next step but not fully determined. Theoretically it should be no problem but I m not starting the test yet.

I also think 5.8GHz video link is also a good choice, assuming the RC ctrl is 2.4GHz hopping + 868MHz wireless data link.

• ▶ Reply

Permalink Reply by Alex on December 31, 2009 at 11:23pm

I dont know what is the cellphone bandwidth is US, 900MHz or 2.4GHz?

If 900 is for cellphone, I guess maybe there is some interference. (correct me if I m wrong)

• ▶ Reply

Permalink Reply by Alex on December 31, 2009 at 11:23pm

Many thanks for your experience and suggestion.

I did the test in a open soccerfield with quite clear line of sight. For the antenna, I use the one coming with the XBee development kit.

I will do more test and update my result here.

• ▶ Reply

Permalink Reply by Earl on December 31, 2009 at 11:37pm

I have used 868 XBee and 900mhz video with no problem.
Earl

• ▶ Reply

Permalink Reply by Riccardo Kuebler on January 1, 2010 at 12:57am

Hi,
are you meaning use 868MHz XBee for Ardupilot telemetry download?
There was a discussion here some time ago, because it seems they don't work for this. They have a duty cicle of 10%.
Is there anyone using them successfully?

Ric

• ▶ Reply

ModeratorPermalink Reply by Sgt Ric on January 1, 2010 at 1:10am

I thought there was a work-around for the duty cycle issue?

• ▶ Reply

Permalink Reply by Earl on January 1, 2010 at 1:40pm

Oh yes they work fine with Ardupilot !
Earl

• ▶ Reply

Permalink Reply by Riccardo Kuebler on January 4, 2010 at 5:39am

Earl,

could you please show a link to the devices you use and some more info about their connection to Arduilot?

Thanks,

Ric

• ▶ Reply

Permalink Reply by Dr Mike Black on January 4, 2010 at 4:00pm

Earl,

i think you have hit on somthing here, that im also not sure of...

in a rash moment, i aquired a 2w 868 - 950mhz Vtx, and we also have a 1w Data 900 mhz Tranceiver.

If the Vtx was set to 868 or 950, do you recon that it will bleed all over the data?

We have used both with success but not together, (always testing somthing new and not putting them together as we originally planned)

is there enough room to stop the bleed over?

no expert on Radio systems

Doc.

• ▶ Reply

▶ Reply to Discussion

• ‹ Previous
• 1
• 2
• Next ›
• Page