Featherweight GPS Trackers in Multi-Stage Rocket

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dratliff

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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
 
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.
 
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.
 
... 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.
 
...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
 
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.
 
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)
 
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.
 
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
 
I just ran a quick test with one base station and two trackers. I turned the trackers on and let them get a good satellite lock. Same with the base station. Once the base station had established comms with the first tracker, I used the selector wheel at the bottom right of the GPS page to switch to the second tracker. It... sorta worked. Sometimes it would connect to the 2nd tracker in just a few seconds, other times it took up to a minute. But when I switched back to the first tracker it would connect within a few seconds. But back again to the second tracker and it would take a much longer period of time, from 10-15 seconds, up to a full minute.

So, I suppose you could connect to booster tracker first, then the sustainer second. Assuming the booster lands first, you could track it and then switch to the sustainer. But that would be pretty risky and you would not get any flight data from the sustainer until much later in the flight.

Here's what the website says:
  • Monitor two or more stages with one phone app and one ground station.
  • Easily switch channels to monitor each stage.
So it appears the way I was testing it is how it is supposed to work. But, the image right above those bullet points does show two base stations connecting to one phone. I noticed that there is a selection wheel for the ground station, so maybe the web site is supposed to read 'easily switch between two ground stations each tracking a separate stage'. That makes more sense since only the bluetooth connection needs to switch, not the long-range connection between the tracker and rocket. And that matches what the picture shows. But to test that I'll need to borrow another base station from someone.


Tony
 
I brought up this issue years ago but they have left the same misleading info on the website and haven't developed proper documentation after all this time. It has been out what 5 years now and still in beta through testflight.
 
I brought up this issue years ago but they have left the same misleading info on the website and haven't developed proper documentation after all this time. It has been out what 5 years now and still in beta through testflight.
Could you point me toward what is misleading?
 
I've brought this up before Adrian, but claiming your tracker will work all the way to space when it has a uBlox M8 chipset that stops reporting fixes above 50km seems somewhat misleading to me. In reality you'd lose tracking at ~165k feet, not 300k+.1660012282403.png
 
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