Wanted to put some thoughts out about options for redundant copter tracking technologies.
We currently use a Garmin Astro ($499.99 on Amazon) 'dog tracker' as a redundant tracking and telemetry system on all of our copter flights. We remove the tracking beacon from its rubberized collar and mount it to the underside of the copter, adding about 6 oz (170 g) to the total flying weight. We are then able to track the location of the copter on the hand held Garmin GPS unit with a 5-second refresh rate. We keep this on in the event that we ever have to find the copter and it was vital for rescuing an Octo in the tropical rainforest of Panama. This can also be used as a redundant telemetry system as the GPS shows the location of the copter and its speed. We have not experienced any radio interference as the 3DR telemetry kit is operating in the 900 Mhz range, the Spektrum controller is at 2.4 Ghz, and the tracker is in the 150 Mhz range. In Panama we found we were able to maintain signal link at 1km from the ground station through dense tropical rainforest.
But the system is expensive and I have been looking into alternatives. I am checking out the RoamEO GPS pet tracking system ($179 on Amazon) and hope it can prove to be a cheaper alternative. The product page lists the collar weight at around 6 oz, the same as the Astro tracker, but I wonder if we can reduce that weight by removing some of the 'collar' pieces. It should arrive in the mail soon, so hopefully we can test it out!
Any one else have any ideas for alternate tracking?
A little update on the RoamEO tracker. I removed a lot of extra parts on the collar and got the weight of the tracking beacon down to about 130g, 10g less than the Astro beacon and roughly the same dimensions. I tossed it in the woods with the GPS antenna pointed down and drove away in my car with the handheld. I got to about 425 m (1400 ft) away before the signal cut out. I then drove a few miles away and came back to the site from a different direction and with the handheld still running. It continued to point me to the last known location of the beacon the entire time and the signal returned when I was about 200 m from the beacon, leading me straight there.
I think if you already have a Garmin GPS unit, the RoamEO might be a cheap solution for back-up tracking. The only downside I can see right now is that tracking is the only thing the RoamEO can do. There is no map or any other telemetry data like speed, lat/long, or elevation, it only tells you how far away and in what direction the beacon is and whether the beacon has connection with the handheld, the beacon's battery life, and GPS status. If you need a tracking solution and could use and afford a Garmin handheld GPS, then the Astro is probably the way to go.