GPS Rocket Locator program Tips

[davdue]

You don't need cell service to use the Android with your Eggfinder. We use both the Android and the LCD RX. Sharon downloaded aerial maps into the Android for the area around the Rocket pasture in Argonia, KS and we used them to find the easiest approach to the location shown on those maps. With the wind conditions there, sometimes the final landing spot was a bit downwind from where the last packet was sent from, but if you have the RX with you, it will pick up the TX and update the location when you get close to the rocket. I have also used the upgraded LCD RX with the GPS chip to walk to the rocket, both methods work, but having the maps on the android is very handy.

By don’t need cell service do you mean signal or don’t need a cell provider and a functioning SIM card?

 

[davdue]

Deleted extra post

 

[davdue]

Deleted extra post

 

[Wayco]

By don’t need cell service do you mean signal or don’t need a cell provider and a functioning SIM card?

No provider or sim card. Just a bluetooth module (HC-06) attached to your LCD RX.

 

[ksaves2]

You don't need cell service to use the Android with your Eggfinder. We use both the Android and the LCD RX. Sharon downloaded aerial maps into the Android for the area around the Rocket pasture in Argonia, KS and we used them to find the easiest approach to the location shown on those maps. With the wind conditions there, sometimes the final landing spot was a bit downwind from where the last packet was sent from, but if you have the RX with you, it will pick up the TX and update the location when you get close to the rocket. I have also used the upgraded LCD RX with the GPS chip to walk to the rocket, both methods work, but having the maps on the android is very handy.

If one wants a little more piece o' mind, a 900Mhz Yagi will pick up positions "sooner" rather than later with a rocket on the ground. I've been told that attempts with inflight tracking with a Yagi might be difficult as the beamwidth is supposedly more narrow on this band and might be hard to keep pointed in the right direction with an out of sight flight. Once the rocket is down though it's generally stationary and easier to point a Yagi. One can prove it when they go out to a rocket.
Use a Yagi for the recovery and as soon as you get a signal, put the stock antenna on. Every time I tried that, the signal disappeared. Now of course I would have eventually been close enough to get a final position but a Yagi can increase the ground footprint. If using a 100mW tracker for a rocket expected to land a few miles out, it could give a little edge if there is no rocket seen at the last known position.

For extra gain for in flight tracking try a 900Mhz patch antenna. Kurt

 

[Donnie]

So, just getting into tracking (have an eggfinder mini / LCD combo to build soon), and am planning to test it out on some mid-power flights to around 1500-1800'. Is this 'high enough' to have enough time to regain GPS lock if lost during boost? Just curious... not sure if this is the absolute best thread to ask this question, but seemed mostly on topic regarding the subject at hand.

Thanks,

Donnie

 

[cerving]

If you're launching to 1800' you'll probably never lose lock.

 

[ksaves2]

Except if the reception of the satellites is questionable. As soon as the main opens there should be a reliable stream. For higher flights under drogue, as long as the rocket isn't flipping around or spinning around (we've all seen some nauseating camera footage under drogue) you should see some positions come in. Things really settle down once under the main chute and in fact if you have a large venue, it's smarter to blow the main as high as you can tolerate because your propagation is better and if tracking on a map, you'll develop a drift trend down low you can follow if you happen to get to the final position report and don't see the rocket. Just proceed in the direction your map suggests and you'll likely get a new final position.

Flying low with an eggfinder is absolutely perfect insurance you'll be able to learn the idiosyncrasies of the system and have the ability of doing a purely visual recovery if something goes wrong. Plus even if it lands close, if it's down in vegetation it will help a lot. Be sure you put a noisemaker on the harness if you have the room.

I had a ballistic flight with a small rocket that wasn't much above 1200 feet and I didn't see anything, nada, not a thing. I got two positions that were not close to the launchpad and nothing in between. I walked to the point farthest from the pad and there was the Formula 54 fincan sticking out of the ground. Had to get a new EggFinder as it died in the process of finding the rocket but the rocket still flies after I busted the nosecone getting it out of the ground. Otherwise it would have just needed a new Eggfinder. Small rocket at a relatively "low" altitude might not get a visual on.

I've punched many a Beeline APRS tracker to totally sight unseen flights and it's a very nice feeling to walk right up to the rocket lying on the ground obvious the recovery systems worked. The NMEA trackers do very good too.
About the only minor beef is the altitude reporting is not that great but the primary purpose is to find the rocket. The APRS stuff is better in that regard but requires a Ham license and more money for the equipment.
But, it's nice to get a live altitude readout plus have the positions plotted on a map live. I haven't had a chance yet to run a Ublox based NMEA tracker yet on a flight but perhaps that might improve the live altitude reporting.
Again, one can always get the altitude off the altimeter once the rocket is recovered (or fly the electronics that do live telemetry) but with a reliable direct readout, one can infer the drogue is out and also a successful main deployment
without a visual on the rocket. I've had that experience many times with the APRS trackers. Sometimes with the 100mW NMEA trackers it's not so apparent the inference of the flight events that is. Kurt

 

[plugger]

So, just getting into tracking (have an eggfinder mini / LCD combo to build soon), and am planning to test it out on some mid-power flights to around 1500-1800'. Is this 'high enough' to have enough time to regain GPS lock if lost during boost? Just curious... not sure if this is the absolute best thread to ask this question, but seemed mostly on topic regarding the subject at hand.

Thanks,

Donnie

I wouldn't expect you to lose lock unless you break Mach, which isn't easy given your comments about the flights being mid-power. I'd be surprised if you lost lock at all. That said I don't own nor have I used an eggfinder mini so ymmv.

 

[Donnie]

Except if the reception of the satellites is questionable. As soon as the main opens there should be a reliable stream. For higher flights under drogue, as long as the rocket isn't flipping around or spinning around (we've all seen some nauseating camera footage under drogue) you should see some positions come in. Things really settle down once under the main chute and in fact if you have a large venue, it's smarter to blow the main as high as you can tolerate because your propagation is better and if tracking on a map, you'll develop a drift trend down low you can follow if you happen to get to the final position report and don't see the rocket. Just proceed in the direction your map suggests and you'll likely get a new final position.

Flying low with an eggfinder is absolutely perfect insurance you'll be able to learn the idiosyncrasies of the system and have the ability of doing a purely visual recovery if something goes wrong. Plus even if it lands close, if it's down in vegetation it will help a lot. Be sure you put a noisemaker on the harness if you have the room.

I had a ballistic flight with a small rocket that wasn't much above 1200 feet and I didn't see anything, nada, not a thing. I got two positions that were not close to the launchpad and nothing in between. I walked to the point farthest from the pad and there was the Formula 54 fincan sticking out of the ground. Had to get a new EggFinder as it died in the process of finding the rocket but the rocket still flies after I busted the nosecone getting it out of the ground. Otherwise it would have just needed a new Eggfinder. Small rocket at a relatively "low" altitude might not get a visual on.

I've punched many a Beeline APRS tracker to totally sight unseen flights and it's a very nice feeling to walk right up to the rocket lying on the ground obvious the recovery systems worked. The NMEA trackers do very good too.
About the only minor beef is the altitude reporting is not that great but the primary purpose is to find the rocket. The APRS stuff is better in that regard but requires a Ham license and more money for the equipment.
But, it's nice to get a live altitude readout plus have the positions plotted on a map live. I haven't had a chance yet to run a Ublox based NMEA tracker yet on a flight but perhaps that might improve the live altitude reporting.
Again, one can always get the altitude off the altimeter once the rocket is recovered (or fly the electronics that do live telemetry) but with a reliable direct readout, one can infer the drogue is out and also a successful main deployment
without a visual on the rocket. I've had that experience many times with the APRS trackers. Sometimes with the 100mW NMEA trackers it's not so apparent the inference of the flight events that is. Kurt

Thanks for the detailed reply. Planning to try it out at a regional launch next weekend. Would like to get a mid-power flight or two, then will likely see if someone's interested in letting it ride along on a higher / faster flight.

I do have a microbeacon that I'll fly on the harness as a noisemaker.

I also plan to try it out on a night launch that same weekend, 'just because.' I think it's similar to practicing 'under the hood' for an instrument license... of course, I'll also have the microbeacon on then as well (pulsating tone and flashing LED).

Couple of follow-up questions:

1. Is there a certain projected speed that is a general rule of thumb with these trackers as to when they'll lose GPS lock (assuming 'good' satellite reception)? Is it mach, or quite a bit lower?

2. You mentioned that 'as soon as the main opens' there should be a reliable stream... is this usually on the order of a few seconds, 5 seconds, 10 seconds, 30 seconds? That's my main question... if I DO lose lock, I don't have a really good feel for how long it 'should' take to find it again under the chute.

Thanks again,

Donnie

 

[cerving]

If you're going high and fast, you're probably going to lose the lock at launch and regain it sometime on the way up as the rocket slows down near apogee. It's dependent on the number of satellites and their position... if they're nicely dispersed then if your rocket is moving around a lot it won't matter as much. If you're flying at a nice flat desert site, you're probably going to see a lot of satellites because you have a full 360 degree view of the horizon; if you're at a field with a bunch of trees surrounding you, it won't be as good.

 

[ksaves2]

Look at the specs of most GPS chipsets and they are guaranteed for 4G's. Yes at really high speeds 1200mph, > 59,000 feet they are supposed to lock out but at high speeds the doppler effect can impair the chipset to decipher the signal
and it might not work well even before it breaks the limits.

Some chipsets will of course work above 59,000 feet as long as the speed is under the limit. Some chips will lockout if one or the other is exceeded and should be avoided if altitude reporting is desired.
For sport flying just to find a rocket about any chipset can be used and will work at the task.

Also on descent, if the rocket is tumbling and at a distance, positions can be lost. I've seen it with EggFinders I've seen it with Beeline GPS's of both power levels. The bottom line is enough positions are received to find a rocket and develop a drift trend down low. Some flights one might see more positions recovered than others. It's voodoo sometimes but I've never lost a rocket that had a functioning GPS tracker except when I had an apogee failure of the drogue and high speed main deployment. That lost rocket also had metallic paint that shielded the Rf and stupidhead didn't do an adequate range test. Rocket was found eventually and got the remains back a year later. GPS does have an edge when it performs well.
(Don't shear the battery cable on boost though because I've seen that ruin a fliers day. Took him hours to find the rocket after a sight unseen flight to 12k'.) Kurt