5 replies to this topic

[mnuapel]

Hello guys,

what do you think about this board? It looks like it could be directly used for passing telemetry via GPRS network and reach infinite control range.

http://www.u-blox.co...nce-design.html

Michal

[K Wells]

Wish Pip was here, Brian should look at this for his project

[Brian]

I have access to one of these, but we haven't even fired it up yet.  I really should try it...

[dankers]

I don't know a lot but I know some bits from a conversation with Ligi some time back. Ligi is the author of Dubwise for Android, one of the cool things he thought of instantly was using GPRS for telemetry, with OP we could even do this with IP. However, the problem seems to be with using GSM at any real height, all the antennas point down slightly so as to give better reception at street level, this cause a lose of signal at anything above 100 meters.

So in theory it should be perfect, almost infinite telemetry like the original poster said in practice it doesn't seem to work at height.

I can confirm this a little bit as I did a high altitude balloon launch a couple of years back and started out close to Melbourne, the way were going to find the balloon was with a GSM tracker that would SMS you its location once it got a phone call, this was tested on the ground before launch and it worked. I tested it again very shortly after launch with the balloon certainly less than 200 meters and it went to voicemail, this was in the middle of a big city. The 900Mhz Xbee's however worked to over 80,000ft (15 miles) and I think only stopped then as the GPS stopped working at that height.

[XXL-Wing]

The ublox devices are great, we use them in many projects. Superb quality and stable. At the same time they come at a fair pricing.
So if it  comes to GPS/DGPS or GPRS/UMTS i would always recommend using ublox devices.

Edited by XXL-Wing, 14 January 2012 - 07:49 AM.

[mnuapel]

dankers, on 14 January 2012 - 12:51 AM, said:

I don't know a lot but I know some bits from a conversation with Ligi some time back. Ligi is the author of Dubwise for Android, one of the cool things he thought of instantly was using GPRS for telemetry, with OP we could even do this with IP. However, the problem seems to be with using GSM at any real height, all the antennas point down slightly so as to give better reception at street level, this cause a lose of signal at anything above 100 meters.

So in theory it should be perfect, almost infinite telemetry like the original poster said in practice it doesn't seem to work at height.

I can confirm this a little bit as I did a high altitude balloon launch a couple of years back and started out close to Melbourne, the way were going to find the balloon was with a GSM tracker that would SMS you its location once it got a phone call, this was tested on the ground before launch and it worked. I tested it again very shortly after launch with the balloon certainly less than 200 meters and it went to voicemail, this was in the middle of a big city. The 900Mhz Xbee's however worked to over 80,000ft (15 miles) and I think only stopped then as the GPS stopped working at that height.

That is true, GSM network is definitelly not designed to cover the air. However at 200 meters outside urban area there should be no problem. what I have read, GSM network is definitelly lost in the altitude of several km. One baloon launch reported the the loss of GSM at 5km. Of course this cannot be considered true everywhere and reliability won't be big.
In cities it can be worse, since the network cells are very small and this the antennas have high directivity. Another problem in city is that at higher altitude the receiver suddenly sees 10s or 100s of networks and it not always can handle this situation.

It would be worth experimenting more with that, but i believe thatin normal altitudes where we fly this should be usable for telemetry and flight plan control.
Ideally would be to have combination of both - xbee network that will work for eyesight and high altitude, and this gsm for backup when it gets out of range at low altitudes.