[Canberrauav] antenna tracker Chris Gough christopher.d.gough at gmail.com Mon Apr 11 14:00:44 EST 2011 Hi Guys, I have decided to make a tracking antennas, is anyone else working on this?. For the OBC, I expect a tracking cluster of antennas on a mast will be the go, driven by something like chunky Dynamixel servos. What I'm going to make first is very different. Small, portable, quick to set up, using standard hobby servos connected to a laptop (via a Polu USB->PWM board). One candidate is a 2.4 GHz patch antenna because I have a couple in my shed (circular polarised, from memory <10cm square). Or it will be a 915-930 MHz waveguide (with shelf for an XBee) because I think that would usefully improve security, especially with a mesh topology. I'm doing this because I have a couple of ideas that I want to try out in software, but I also want to start collecting practical experience with tracking antennas. The reason the analog video reciever is a candidate is because it seems simple enough compare two RSSI voltages to quantify the relative performance of two antenna/reciever combinations (and I think the video recievers have a RSSI pin). I asusme there are ways to do this with XBees too but don't know how to log signal strength, dropped packets, etc. Any hints? (is there something like NetStumbler for XBee?). WiFi would be good for this stuff but to begin with I want a rig that doesn't need a computer in the plane for testing/development (obviously this will become less of an issue as we progress). Chris Gough
[Canberrauav] antenna tracker tridge at samba.org tridge at samba.org Tue Apr 12 10:02:34 EST 2011 > I have decided to make a tracking antennas, is anyone else working on this?. not as far as I know. > I asusme there are ways to do this with XBees too but don't know > how to log signal strength, dropped packets, etc. Any hints? (is > there something like NetStumbler for XBee?). I'd be inclined to do it with the Xbees we're currently using to talk to the planes. It seems that Xbees have a RSSI pin encoded as PWM: http://log.liminastudio.com/itp/physical-computing/measuring-xbee-signal-strength-from-the-rssi-pin I wonder if we can just connect that pin to one of the spare servo input pins on the APM in the plane, and measure signal strength that way? We could then send that data as a mavlink packet down to the ground station. Similarly, on the ground, we could use an arduino to measure the ground stations signal strength. Cheers, Tridge
[Canberrauav] antenna tracker Chris Gough christopher.d.gough at gmail.com Tue Apr 12 11:50:31 EST 2011 Hi Tridge, > http://log.liminastudio.com/itp/physical-computing/measuring-xbee-signal-strength-from-the-rssi-pin Bingo, thank you. Xbee it is then. > I wonder if we can just connect that pin to one of the spare servo > input pins on the APM in the plane, and measure signal strength that > way? We could then send that data as a mavlink packet down to the > ground station. nice idea, don't see why it wouldn't work. > Similarly, on the ground, we could use an arduino to measure the > ground stations signal strength. I have a laptop/polu board to hand (and working software, no RSSI) so will start there. However, if there's going to be another micro in the mix it might as well replace the polu board, especially if future versions involve giant non-PWM servos. Maybe it could eventually even replace the laptop too? it could run the tracking code and pipe serial from the xbee to a socket using an ethernet shield. I'll worry about that later. Chris Gough -- .
[Canberrauav] antenna tracker Jack Pittar jpittar at bigpond.net.au Wed Apr 13 00:46:51 EST 2011 I can help with a heavy duty servo, other servos, or a gearmotors and drive electronics. Jack. -----Original Message----- From: canberrauav-bounces at canberrauav.com [mailto:canberrauav-bounces at canberrauav.com]On Behalf Of Chris Gough Sent: Tuesday, 12 April 2011 11:51 AM To: tridge at samba.org Cc: canberrauav at canberrauav.com Subject: Re: [Canberrauav] antenna tracker Hi Tridge, > http://log.liminastudio.com/itp/physical-computing/measuring-xbee-signal-st rength-from-the-rssi-pin Bingo, thank you. Xbee it is then. > I wonder if we can just connect that pin to one of the spare servo > input pins on the APM in the plane, and measure signal strength that > way? We could then send that data as a mavlink packet down to the > ground station. nice idea, don't see why it wouldn't work. > Similarly, on the ground, we could use an arduino to measure the > ground stations signal strength. I have a laptop/polu board to hand (and working software, no RSSI) so will start there. However, if there's going to be another micro in the mix it might as well replace the polu board, especially if future versions involve giant non-PWM servos. Maybe it could eventually even replace the laptop too? it could run the tracking code and pipe serial from the xbee to a socket using an ethernet shield. I'll worry about that later. Chris Gough -- .
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