# Featherweight GPS Trackers in Multi-Stage Rocket

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#### dratliff

##### Active Member
Greetings all,

I'm having an issue using Featherweight trackers in a 2 stage rocket. I've got 2 trackers paired to the same ground station, the idea being to fly one tracker in the booster and the other in the sustainer. The problem I'm having is that I can't switch between the 2 trackers when both are active. I can see both trackers, but I can only navigate to the first one that was turned on. Once I shut the power off to the first tracker, then I'm able to navigate to the tracker that was turned on last. Anybody else run into this? Am I doing something wrong?

Thanks, Dave

#### Cameron Anderson

##### Well-Known Member
I assume you're setting each tracker to a different channel setting?

#### Voyager1

##### Well-Known Member
TRF Supporter
I have experienced the same problem with my FW trackers. With two trackers recognised and connected to my ground station, I can sometimes switch between the two, but after a couple of switch-overs or data transactions, it will accept only one of them - possibly the the first to be activated. However, I think you might be having a proximity issue. If I re-orient my tracker modules and space them a little further apart from each other, and from the ground station, then they appear to be functioning correctly and are able to be selected independently.

I have been using these trackers for a couple of years now and I think they are great, but the documentation does need to be updated to include the newer features.

#### kjs

##### Well-Known Member
TRF Supporter
So for a two stage flight, you could use one GS and two trackers, but the trackers would need to be on different frequencies and the GS would only be listening to one or the either (and you would need to switch between them as Voyager1 indicated). Better solution is to have two GS and the trackers and GS on different frequencies - and one GS/Tracker on the A 'side band' and the other GS/Tracker on the B 'side band'.. The A/B actually indicates what fraction of the GPS second it is communicating with the tracker and phone. If both are A or both or B, the GS/TRK should still talk to each other, but the phone may have issues with getting updates from both at the same time. I would think the bluetooth could handle that, but not certain how it handles that.

But the side story here is I have a two stage kit that I need to build and I would like to optimize tracking for integrated booster and sustainer... I don't know if TRF is the appropriate place to have the discussion of finding the solution, but agree that it would be the place to post the outcome and methodology.

#### phyzzld

##### Well-Known Member
TRF Supporter
... However, I think you might be having a proximity issue. If I re-orient my tracker modules and space them a little further apart from each other, and from the ground station, then they appear to be functioning correctly and are able to be selected independently...
Does this mean that before a two stage rocket separates, that only one tracker will work? That could be a problem if you wanted to to do a pre launch check of the trackers.

#### phyzzld

##### Well-Known Member
TRF Supporter
...Better solution is to have two GS and the trackers and GS on different frequencies - and one GS/Tracker on the A 'side band' and the other GS/Tracker on the B 'side band'.. The A/B actually indicates what fraction of the GPS second it is communicating with the tracker and phone. If both are A or both or B, the GS/TRK should still talk to each other, but the phone may have issues with getting updates from both at the same time. I would think the bluetooth could handle that, but not certain how it handles that...
I am building a two stage rocket and was planning to use the two tracker one GS method, but you have given me a moment of pause. Needless to say I'm concerned that my planned solution may now be $200,00 more expensive than I thought. The website is confusing, it says only one GS is needed, but the picture shows two GS's being used. Also, how do you use two GS's simultaneously with one iPhone? From your post it seems like maybe that isn't worked out yet? Will the type of phone matter (I have a 6s) or the version of GS (I have a v1)? ...I don't know if TRF is the appropriate place to have the discussion of finding the solution, but agree that it would be the place to post the outcome and methodology. If the discussion is open to anyone, I would be interested. Please let us know when and where. Jeff #### SkywackerJim ##### Member I am fairly new to using the FW trackers and haven’t really had a ”need” to use them but flown them 3 - 4 times just to get familiar with them. I have once or twice flown two in the same rocket. I don’t recall not being able to switch back and forth but I did find that the data from both are combined into one file which I wished were separate. I am planning to fly them in a two stage eventually too. Would really like the data to be separated. #### ksaves2 ##### Lifetime Supporter TRF Lifetime Supporter Ummmmm, The fail safe method is to have two trackers on two frequencies that aren't close to each other and two separate receivers with a GPS. Yeah, I know it's pricey but having to switch back and forth on the receiver end is not practical in a real time flight. Technically on the 70cm (400Mhz) Ham band it would be doable in APRS but if one is tracking the booster, what is happening with the sustainer? It would be better to have a friend familiar with GPS tracking, run a receiver to track the booster and you the flier have a system on a different frequency track the sustainer. That part of the rocket is really going to be flying high and you would want to pay close attention more to it if you want to get it back. I've witnessed a few HPR two stage flights and most of them, the sustainer stays within sight. If your project is such that the booster is going out of sight, you'd best be served with two ground stations tracking each component with two people monitoring the status. On the other hand, if you don't expect the booster going out of sight and want to use GPS/APRS tracker to assist with ground recovery due to terrain, I think channel switching would be doable. Have a person visually track the descent of the booster so you would have a ground bearing to walk towards it and you can then stay on the sustainer frequency for the flight. Otherwise if both parts of the rocket are expected to be going out of sight, two independent trackers and receivers would be the best investment if you want to get both components back. Kurt Savegnago (a.k.a. KC9LDH) #### Cameron Anderson ##### Well-Known Member I am building a two stage rocket and was planning to use the two tracker one GS method, but you have given me a moment of pause. Needless to say I'm concerned that my planned solution may now be$200,00 more expensive than I thought. The website is confusing, it says only one GS is needed, but the picture shows two GS's being used. Also, how do you use two GS's simultaneously with one iPhone? From your post it seems like maybe that isn't worked out yet? Will the type of phone matter (I have a 6s) or the version of GS (I have a v1)?

If the discussion is open to anyone, I would be interested. Please let us know when and where.

Jeff
There isn't a good way to track separate trackers with different ground stations on one phone. You'd have to switch from freq to freq, which is more cumbersome than you think it would be. The picture on the website is...accurate, but less than transparent.

#### phyzzld

##### Well-Known Member
TRF Supporter
There isn't a good way to track separate trackers with different ground stations on one phone. You'd have to switch from freq to freq, which is more cumbersome than you think it would be. The picture on the website is...accurate, but less than transparent.
I agree that the website and documentation is short on details about this feature. It appears my assumptions about how it worked aren't too good either. I think it would be good to hear from Adrian or Kevin about how they intended the "Multi-Stage" feature to work.

Jeff