Here's an actual example of mine from last year of what I noted above.
A tracker like this is imo invaluable if you launch anywhere where you can lose sight of the rocket.
Last year I was using a TRS (older Eggtimer altimeter that has GPS tracking and I also linked it to a handheld Eggfinder Rx unit) and my 4" Patriot on an I600 had the main deploy at ~2700' (still not sure why, but have a few leads).
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It went far away behind a grove of trees (in the right background of the above pic) and landed in some different section of the farm.
Hours of searching was fruitless. I had GPS coordinates on my rx, but no phone service out in the far fields and it was getting dark, so I left.
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When I got home, I plugged the coordinates in and got a spot right away.
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The next morning I went to that spot and it was right there! It was smack dab in the middle of a field and laid low, so it was just far enough from every side path for it to not be visible.
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That saved me a big rocket, plus casing and dual altimeters!
This year I know better to get a GPS map of the area beforehand or get to an area with phone reception.