Some preliminary results -- unfortunately my wife had the flu the weekend I was planning actual launch tests. So, I have some ground test results, but it will be a while before I get the chance to launch again.
GENERAL- Seems pretty solid. Heavy rubber collar and a reasonable seal around the GPS unit and battery compartment.
- It does not require any modifications for my application. (For example, the Garmin unit cannot be easily mounted in a 3" airframe without moving the antenna.)
- It does have an external antenna. The antenna is built into the collar.
- It is about 12 inches long. You might be able to shorten it a bit, but I did not want to start cutting wires (at least not yet.)
- About 2 inches wide. Fits easily in a 3" airframe.
- Battery duration was pretty good. Both the collar and the reciever were left on overnight. The receiver ran out of juice at about 18 hours and the collar was showing just a little life left at that time.
- All tests conducted with the collar double-wrapped in a Nomex chute protector as that is how I intend to use the unit. (Nomex "pocket" attached to the shock cord.)
- To test the ability to track the unit with a lot of obstruction, the collar was left behind my house. In addtion to the house, several trees, bushes, and a six foot brick wall between the collar and receiver.
- YES, the key to successful use is the ability of the receiver to regain the signal from the collar. If you get a lock while the unit is sitting in your rocket on the launch pad, and the receiver losses the lock immediately after lift-off, the receiver will think the rocket is still on the pad.
- SO, how close do you need to be to regain a lost signal? With the obstructions noted above (Nomex, house, trees, brick wall, etc.):
-- ~1300 feet with the collar just in the Nomex laying in some grass
-- ~700 feet with the collar in the Nomex, INSIDE a 3" Blue Tube airframe
-- ~400 feet with the collar in the Nomex, INSIDE a 3" fiberglass airframe
- More testing is needed.
-- Can the unit stand up to the stresses of HPR launches?
-- Will my Nomex "pocket" work? (I, for one, don't want a complex mounting system that makes it difficult to move from rocket to rocket.)
- I think that if you completely lose sight of your rocket and don't have at least a reasonable vector to start walking a search line, this might not work for you.
- But, if you have a reasonable lauch site where you can see your expected landing zone, this has good possibilities.
- As some others have posted, with a less obstructed area the range to re-acquire the signal is about half a mile. Except for the really high-flying stuff, that drifts miles away, getting to within a half mile should be reasonable.
Once I get to actually launch this thing I will post an update.