I've been thinking about (and talking about) and working on the over-the-horizon relay feature for.... a long time now. (years! 
) I think the microcontroller firmware part of it is finally done. As I'm writing this I'm watching my test setup go through a longer-duration test. So I have some time to kill and it seems like a nice time to share:
Introduction:
When you fly your rocket with a GPS tracker, when it lands, it often loses contact because of hills, ridges, etc. getting in between you and the tracker. Standard practice is to go to where the rocket was last heard from. Usually you'll get the signal back as you get closer, and things work. But when you have been enjoying watching your rocket's data come back consistently, and then you just stop hearing from it, an uneasy feeling is natural. Wouldn't it be nice if you kept getting data from your rocket after it lands? Now, you can, if you or one of your friends launches another Featherweight tracker. Nobody has do to anything special, just fly like usual and the systems will automatically get the latest data back to you to see on your phone. If you want to do something special to relay the data, like fly a tracker on a drone or fixed-wing airplane, or a kite, or a helium weather balloon, that will work too, but it's not required.
How does it work?
Every Featherweight tracker spends part of its time listening for lost rockets when it's not transmitting its own location. When it hears from a lost rocket, it includes the found rocket location along with its own location and sends it back to its ground station. When a ground station gets the found rocket info, it broadcasts it to other ground stations that are within range at the launch area, one of which is yours. Your ground station passes it along to your phone using Bluetooth. It will show up on a screen of found rockets, and you can select it to track to that location.
The complicated part is hidden behind the scenes. How do you get all of the pieces to do the right thing, at exactly the right time? The LoRa radio can only do one thing at a time. It can listen, or transmit, but not both. You want your rocket to talk back to your ground station on a dedicated channel without needing to share time on it with anyone else, but for the lost rocket data passing to work, all the trackers and all the ground stations need to be communicating on the same channel at least some of the time. GPS can be used as a common time reference, but getting that to work precisely is easier said than done, and it's also important to have your ground station and tracker start talking immediately when you turn them on, and stay talking, whether or not they have a GPS lock yet. But now it's working, and the longer-duration test has been solid, so time for some sleep.
) I think the microcontroller firmware part of it is finally done. As I'm writing this I'm watching my test setup go through a longer-duration test. So I have some time to kill and it seems like a nice time to share:Introduction:
When you fly your rocket with a GPS tracker, when it lands, it often loses contact because of hills, ridges, etc. getting in between you and the tracker. Standard practice is to go to where the rocket was last heard from. Usually you'll get the signal back as you get closer, and things work. But when you have been enjoying watching your rocket's data come back consistently, and then you just stop hearing from it, an uneasy feeling is natural. Wouldn't it be nice if you kept getting data from your rocket after it lands? Now, you can, if you or one of your friends launches another Featherweight tracker. Nobody has do to anything special, just fly like usual and the systems will automatically get the latest data back to you to see on your phone. If you want to do something special to relay the data, like fly a tracker on a drone or fixed-wing airplane, or a kite, or a helium weather balloon, that will work too, but it's not required.
How does it work?
Every Featherweight tracker spends part of its time listening for lost rockets when it's not transmitting its own location. When it hears from a lost rocket, it includes the found rocket location along with its own location and sends it back to its ground station. When a ground station gets the found rocket info, it broadcasts it to other ground stations that are within range at the launch area, one of which is yours. Your ground station passes it along to your phone using Bluetooth. It will show up on a screen of found rockets, and you can select it to track to that location.
The complicated part is hidden behind the scenes. How do you get all of the pieces to do the right thing, at exactly the right time? The LoRa radio can only do one thing at a time. It can listen, or transmit, but not both. You want your rocket to talk back to your ground station on a dedicated channel without needing to share time on it with anyone else, but for the lost rocket data passing to work, all the trackers and all the ground stations need to be communicating on the same channel at least some of the time. GPS can be used as a common time reference, but getting that to work precisely is easier said than done, and it's also important to have your ground station and tracker start talking immediately when you turn them on, and stay talking, whether or not they have a GPS lock yet. But now it's working, and the longer-duration test has been solid, so time for some sleep.
