Launching a cubesat and using that as a telemetry relay did feature in a recent CanberraUAV meeting … but we don’t have enough money for that
One of the teams (Delft) did have a Iridium modem in their UAV (specs at http://mavlab.tudelft.nl/iridium-communication/) in the 2016 UAV Challenge. They did mention semi-regular dropouts though - as they modem needed to handover from one satellite to the next as the satellites flew over.
INMARSAT doesn’t require satellite handovers, as their satellites sit in GSO orbit (stationary relative to the earth’s surface).
EDIT:
In terms of costs, you get hack together a basic low latency link for <$2000 … depend on your definition of low cost! Satellite ground hardware is getting cheaper and cheaper each year.
Yeah well you just need to find the right sponsor! I think the main issue will be that you’d have to wait some 90 minutes for a few minutes of connection!
I actually asked Bart about that recently. They used a more expensive industrial version of the Rockbloc module and seemingly didn’t have many issues with it. They’re also after a Mozzie atm.
In general I’m not really a fan of satellites for cost/performance. A better option would be a high altitude solar powered persistent drone running Arduplane using mulit-gigabit microwave link…in fact if you do it right like SHARP you could use the microwave energy through a rectenna to power the plane as well! To get around the regs you go out 12NM from the coast until you hit international airspace, which means you can fly up to whatever altitude you like and stay there for however long you want. According to GE you still get LOS comms to Dalby from there…The only thing is it will need to offer a public AP otherwise it would be in trouble with the challenge rules!
Do you know the longest Arduplane has ever flown? I think PX4 done 81hours once with their solar plane? I’ve been meaning to build my solar X8 for a while now.
About the UAV Medical Challenge… Why don’t you just use the same communication channel as the “Joe” when he called the abmulance (which is probably a cell phone these days)? What about using a combination of satellite and cellular?
Joe was in a remote area. Cellular coverage was not guaranteed over the mission area. We had 2 different cellular modems (using different network providers - Telstra and Optus). Each lost signal at some point in the mission, although we did not lose both at the same time.
We only used one 4G modem at the time and went out and tested both the Optus and Telstra networks by swapping static IP SIM cards at the nearest main road near the remote landing site. The Optus network was best there, but didn’t really want to work under 50cm above the ground. Our aircraft was only 2kg and therefore only 25cm high. Didn’t look good.
Our last minute idea was to mount it on one of the main wing tips, and then only have one leg on one side of the aircraft, so when it landed it tipped to one side and so that on the other wing tip with the 4G antenna would be higher off the ground.
Thanks Pavel!
That is actually really useful to see. So about 4-5minutes of no reception being the longest, but a period of about 30minutes of fairly patchy reception. Not Ideal, but probably useable still. How long does it actually take to send a message if it does have reception? 10-20 seconds? And from what signal quality upwards will it still send roughly?
The software does not try send/receive sessions if the signal quality is <2. The sessions usually succeed with signal quality >=2 and take about 10-20 seconds.
I’m curious how antenna affects the signal quality. What makes a good antenna for 1600MHz?
Hmm ok. That makes it a fair bit worse. About 40-45% offline. About 6-7minutes at a time offline. Probably no certainty with the satellite coverage, so it could be up to 30-40min worse case. In air would be probably better, but for the challenge we don’t need it in the air at all with the RFD900 available.
Antenna would be critical, as would RF noise floor and a good ground plane. Not sure what sensitivities they operate at, but it’s probably similar to GPS. Stephen would know more.
Iridium signal power would be higher than GPS (at the Earth’s surface). Any Iridium modems would have had great care taken not to interfere with the GPS.
In summary:
-Iridium won’t interference with GPS, assuming you’re using off-the-shelf equipment
-Noise floor would be similar to GPS
I could not make my RockBLOCK work with GA™ 38 GPS/GLONASS antenna. As soon as the external antenna is attached and the patch antenna is shielded, the signal quality becomes flat zero. It work pretty well though with pretty much any other piece of metal used as antenna.
Thanks for that Pavel. It does give a good indication of the Irdium performance. There’s not to many position points missing from what I can tell on the map. Looks good, I think it should work.
Very cool project. Is there any sort of guide for a total n00b to set this up if you have the hardware (autpilot, RPi, and RockBlock 9603) but no idea where to start?
Hello, I have been following the forum for a long time but it is the first time I have written, since I saw the seacharger project, I wanted to build my own boat controlled by satellite, I have enough knowledge of electronics but not much programming.
more than 5 months ago I build in a boat of 2 meters in length, 4 solar panels of 100w each, with a T200 thruster, 2 batteries lifepo4 12v 50AH, all controlled by pixhawk with the software ardupilot.
all this has worked well, although there are still things to improve, but the most important thing is the satellite communication, I used the envirover software http://envirover.com/
but In my first test had problems with communication, sometimes I lose connection with the boat for periods of more than 2 hours, and this does not feel good.
the envirover team has been very kind, and they have oriented me, I am waiting for a new version to try it, I hope I do not have the problems I said before.
