Counterpoint:
If any system loses power or the radio Rf energy can't get out of the airframe, there's going to be a problem. I remember seeing people free packing a Beeline GPS tracker that's very easy to have the battery power cable loop around behind the pc board.
Push the button, high G flight ensues and board cuts the battery cable. If any system is installed inappropriately there is going to be a problem. Break or distort the antenna in flight and there is going to be a problem. Having a GPS tracker
with an RDF tracker backup is reasonable for projects that have the room.
That said, I've heard of folks with totally sight unseen high powered filghts that couldn't keep an RDF bearing locked and lost the rocket. Try as they may, they couldn't get within the ground footprint of the tracker. Out on the playa, the ground footprint
is very short. I've been told that a reasonably powered GPS tracker is mandatory for completely sight unseen flights there. Listen, if one can get a visual on any rocket in the terminal phases on descent under the main chute, doesn't matter whether
it's a GPS tracker or RDF tracker, as long as they're working you are going to get it back. You can see right off where to proceed.
The edge of GPS is one has the potential of getting a position on a map when the rocket is so many feet in the air. It's likely going to have to be higher up the farther out the rocket is. Nonetheless, a position from 100 feet in the air or lower is likely going to get one within the ground footprint of the tracker for terminal recovery. Especially if it's a totally sight unseen flight. RDF, you got a bearing and no distance. GPS you got a bearing and distance.
One other GPS advantage that is totally lacking with RDF is with an off-nominal or ballistic flight. Experience that and even if the rocket is a few hundred feet in the air when the last position is received, walk to it and there is a good chance you'll find the hole
or the pieces. I'm talking totally sight unseen. One might be able to salvage most of an FG rocket in that case. RDF? Unless one can keep the bearing and keep walking (there is no idea of the range) they are SOL because the tracker (GPS or otherwise) dies on the hit.
A possible mistake with any tracker is using the wrong device with an aggressive flight profile. 900Mhz doesn't have the best propagation period. Someone is going to lose an EggFinder (if it hasn't already happened) or some other 900Mhz GPS tracker because they used it in an extremely high flying rocket that drifted too far. That's the bad news. The good news is for most sport fliers that's not the issue because one is not routinely sending sport rockets up to 20,000' with a 1 mile diameter launchsite radius. Sport fliers have no trouble tracking no matter what is used because their rockets land relatively close. (Multtronix is in a league by itself and uses higher 1 watt power
on 900Mhz.)
Rich is a dedicated RDF guy and I've done some of that but I'm lazy and find if I can go get the rocket without diddling around, I can get back quicker with a properly functioning GPS tracker than with an RDF one. Again, if at any time one sees the rocket on the terminal descent under main, all bets are off. One is going to find it no matter if GPS or an RDF tracker is used. You see an RDF rocket coming in, one can use a handheld GPS with a "Sight 'n Go"
feature to lock in the bearing to proceed. I wear an Etrex Vista HCX around my neck at every launch for that that purpose (good for modrocs too) Take the Yagi antenna, radio and attenuator with you and you'll get it back.
Totally sight unseen flight there is an advantage with a GPS tracker as long as one receives positions on descent. A GPS tracker generally settles down once the main chute has blown and the descent speed has slowed down.
A good strategy here is to blow the main chute up higher rather than down lower so one has the advantage of better propagation and more time to develop a drift pattern before LOS (loss of signal). This might be more important if one
expects the rocket to land a fair distance away.
Another bit of advice is put a screamer on the harness no matter what you use, GPS or RDF. In standing vegetation one's hearing (if intact) beats any GPS or RDF any day!
If one wants the absolute "best range", get a Ham Ticket and use 70cm or if you have the room in the rocket, a 2 meter tracker:
https://www.radioddity.com/sainsonic-ap510-aprs-tracker.html#
https://www.tracksoar.com/
I kinda am leary about the small GPS antenna on the tracksoar as it's meant for a sedate balloon flight
https://www.db1nto.de/index_en.html
https://www.hamradio.com/detail.cfm?pid=H0-015928
All of the above take a Ham ticket and again, if one one is not routinely going above 10k with a lot of vegetation around, or a significant drift distance, the unlicensed trackers should be fine.
The LoRa technology in the upcoming Featherweight offering would be about the "highest" end of the low end trackers. It will probably be one notch below Multitronix and more affordable. Looks like the cost of two (the minimum needed to track) would be about what a Beeline GPS Ham tracker would cost although the price might go up the more time it takes to develop. Stay tuned. There was nothing but APRS in 2005 and it was all Ham and it cost.
(There were I believe a couple of 900Mhz GPS trackers back then but the cost was pretty steep. Much more $$$ than getting a Ham license and getting the Ham equipment.)
One other tidbit. Don't use a 900Mhz Yagi antenna to try to track a rocket in flight. The beamwidth is very narrow as compared to 70cm, 1.25M and 2M hence people flying transmitters on those bands can use
Yagis for in flight monitoring. A cheap 900Mhz Yagi is still a decent tool for ground recovery as the rocket isn't moving so fast and it's easier to aim at a stationary target. Proved it to myself a couple of times.
Used a 900Mhz Yagi to recover a TRS on one flight and an EggFinder on another flight that were completely sight unseen. Screwed on the Yagi cable to the EF LCD and pointed the Yagi horizontally in the direction
of flight after looking on the map. Proceeded to the rocket and once the signal was reacquired (still couldn't see the rockets either) I put the vertical dipole (or duck antenna) on the receiver and the signal
disappeared. Sure, I was going to find the rockets anyways and the Yagi wasn't needed but if the recovery was under more difficult circumstances, ie. rocket drifted farther than expected and one had to resort to
following the drift pattern the larger ground footprint afforded by the Yagi could be a recovery saver. Any "edge" one can acquire with a recovery system is just cheap insurance at getting a rocket back.
Kurt