# Keychain GPS Trackers?

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#### eduncan911

##### Active Member
Saw the recent $25 build thread for a GPS tracker and it made me think of this keychain GPS+SMS+3G device (uses direct line-of-sight GPS). But, it needs 3G to transmit back. Where we launch, and even the local club areas, have full 4G/LTE/3G coverage. Given, it's not$25 (you can get it cheaper on eBay from overseas for about 1/2 the price).

My daughter recently bought me a Comanche 3, 3 stage rocket. Besides it hitting around 2300 feet... A part of me wants to do all 3x 24mm motors. And a G55 in the sustainer with two F24s means it gets to... gulp... 8100 feet. (modeled in OpenRocket - will publish the file soon for others).

It's a 24mm diameter tube. So something going even 2000+ feet makes me think I'll lose it.

So here's my thought...

* Get one of those GPS keychain.
* Disassemble it, strip it down to bare and hope it fits in the 24mm tube.
* Attach it to the nose-cone/payload area, along with a tiny altimeter.
* Launch.

When on the ground, I can SMS it to get its GPS location and/or their realtime software (which I am sure is pretty bad anyways).

I was thinking more complicated setups could use an Adafruit coprocessor (about the side of two dimes side-by-side) that I could program for the accelerometer to "stop" - and once idle, activate the SOS button to send a GPS to phone like every 5 minutes. But trying to keep the weight down.

#### CORZERO

##### Well-Known Member
Mine is still smaller than yours! Not every day you hear that from a guy, right?

Really though, this sounds like quite an ambitious project! 8k Comanche? Hell yeah! Even stripped down though I would wager that a 3DR with a wire antenna and a small lipo still weighs in less dimensionally and in mass. I have limited experience with GSM tracking, and I have concluded that ersatz GSM/GPS trackers are either junk or inappropriate for our arena. The types I am aware of are 1) no GPS antenna, network-only location and 2) true GPS with GSM (having a GPS antenna).

I looked at your tracker and am not sure what its functional capabilities are. If GSM only (with no GPS antenna), my concern would be reception at that altitude. You may lose signal. If true GPS (with a GPS antenna), well I'm just not sure. At $140 I would assume it is true GPS. Test and let us know. I would recommend Ting for you provider if you decide to go this route. I have kept their service for the last couple of years as a backup and the company is good to go. https://ting.com/ That's my 2 pence, but I'm sure it's only a matter of time before Ksaves drops a dime on us and scrambles your brains with another wall of text capable of testing TRF server storage integrity. Love ya Kurt Last edited: #### ksaves2 ##### Lifetime Supporter TRF Lifetime Supporter Mine is still smaller than yours! Not every day you hear that from a guy, right? Really though, this sounds like quite an ambitious project! 8k Comanche? Hell yeah! Even stripped down though I would wager that a 3DR with a wire antenna and a small lipo still weighs in less dimensionally and in mass. I have limited experience with GSM tracking, and I have concluded that ersatz GSM/GPS trackers are either junk or inappropriate for our arena. The types I am aware of are 1) no GPS antenna, network-only location and 2) true GPS with GSM (having a GPS antenna). I looked at your tracker and am not sure what its functional capabilities are. If GSM only (with no GPS antenna), my concern would be reception at that altitude. You may lose signal. If true GPS (with a GPS antenna), well I'm just not sure. At$140 I would assume it is true GPS. Test and let us know. I would recommend Ting for you provider if you decide to go this route. I have kept their service for the last couple of years as a backup and the company is good to go.

https://ting.com/

That's my 2 pence, but I'm sure it's only a matter of time before Ksaves drops a dime on us and scrambles your brains with another wall of text capable of testing TRF server storage integrity. Love ya Kurt
No problemo. But if one uses anything that requires the cell phone network they need to be certain they have service at their launch site. If their rocket ends up lying down on the ground with the GPS antenna pointing down it might lose lock so when one calls it for the position it might not have anything to report. It's best to have a live tracking system that's independent of anything else for best reliability. There are folks who've used it with success but I would only use it with sport rockets one doesn't expect to drift far from the launch site.

I keep looking but I still cannot find a simple mapping application that anyone can use which will plot in real time the rocket position without having to wring one's hands over a setup. There are a variety of applications that folks are using with success. The ham radio guys have an edge over this. Kurt

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#### CORZERO

##### Well-Known Member
No problemo.
Two words???? Who is this and what did you do with Kurt???!!?!?!?! :surprised::surprised::surprised::surprised::surprised:

#### ksaves2

Two words???? Who is this and what did you do with Kurt???!!?!?!?! :surprised::surprised::surprised::surprised::surprised:
Sorry messing with a dictation app. Must have pushed a wrong button Kurt

#### cerving

TRF Supporter
<Shameless_Plug>You can get an Eggfinder Mini Starter Set for $125 and it will work anywhere...and it WILL fit in your 24mm tube. It will fit in an 18mm tube if you get the right battery.</Shameless_Plug> #### Wallace ##### Well-Known Member <Shameless_Plug>You can get an Eggfinder Mini Starter Set for$125 and it will work anywhere...and it WILL fit in your 24mm tube. It will fit in an 18mm tube if you get the right battery.</Shameless_Plug>
And it will work. Found mine along with my Quantum after a shred at almost 4000'. Had to pry it out of the pretty well busted up nc and everything still appears to work just fine. Thanks Cris.

#### ksaves2

And it will work. Found mine along with my Quantum after a shred at almost 4000'. Had to pry it out of the pretty well busted up nc and everything still appears to work just fine. Thanks Cris.
Several have posted about recovering ballistic flights with the EggFinders and I'm sure those who fly Missileworks too will also have the same experience.
The Beeline GPS trackers too. Kurt

#### Dugway

##### Well-Known Member
I've flown one of these half-a-dozen times just zip-tied to the shock cord and it worked pretty well:

https://www.aliexpress.com/item/MD-...35mm-with-Collar-SOS-Two-way/32814558171.html

The biggest issues are the size (i doubt very much you could ever fit it in a 24mm tube) and the fact that you have to side-load their Android app. I'm lucky that both our launch sites have pretty descent T-Mobile coverage for the $10/mo data-only SIM card. I don't like that when navigating to the rocket, it tends to spiral you in to the actual location, but that may just be a function of two different GPS's coming to terms with their relative location. I've decided to use this less in the future mostly because my phone kept shutting down in the 100 degree heat at HellFire when the GPS was active. No such problems with my EggFinder/Garmin Rino 110 combo. #### billdz ##### Well-Known Member I've flown one of these half-a-dozen times just zip-tied to the shock cord and it worked pretty well: https://www.aliexpress.com/item/MD-...35mm-with-Collar-SOS-Two-way/32814558171.html Thanks for the link, I've been thinking about trying something like this. At the bottom of the linked page, there's a More Products section which lists several similar products, some as cheap as$6.50, some more expensive, different sizes. I'm wondering if any of these are any good?

Also, with these types of trackers, is it really necessary to activate a new SIM card just for this? Would it be possible just to take the SIM card from my son's phone and borrow it on launch day for use with the tracker?

#### ksaves2

Thanks for the link, I've been thinking about trying something like this. At the bottom of the linked page, there's a More Products section which lists several similar products, some as cheap as $6.50, some more expensive, different sizes. I'm wondering if any of these are any good? Also, with these types of trackers, is it really necessary to activate a new SIM card just for this? Would it be possible just to take the SIM card from my son's phone and borrow it on launch day for use with the tracker? I suspect if the cell phone chipset is compatible with your son's cellphone, it might be possible. If the tracker is GSM and the phone is GSM perhaps. Some else comment? Kurt #### billdz ##### Well-Known Member I suppose it's no different from moving a SIM from one phone to another, like when you buy a new phone. #### Wallace ##### Well-Known Member I suppose it's no different from moving a SIM from one phone to another, like when you buy a new phone. Absolutely with the caveat that certain providers (not all) require that you "register" the sim with their service before it'll work. No cost, but still a pain in the arse. #### Dugway ##### Well-Known Member Watch out, the really cheap ones don't have a GPS on board despite the description. It looks like they use tower triangulation to approximate location. #### billdz ##### Well-Known Member Yes, I noticed that. Dugway, I'm a bit unclear on how that tracker works. You send a text message to the unit and it sends back a text with the rocket's location? What does the side-loaded app do and where do you download it? #### billdz ##### Well-Known Member #### ksaves2 ##### Lifetime Supporter TRF Lifetime Supporter There must be a catch, but FreedomPop is offering a$0.99 SIM card with free monthly 200MB of data, 200 minutes of talk, and 500 texts.
https://www.freedompop.com/offer/si...qfslaavcp-5btGVbi-cHg3AjKBy0IKTBoCxEUQAvD_BwE
That should be enough to handle a few launches with a GPS tracker a couple of times a month, isn't it?
Be extremely careful with FreedomPop. If you give them your credit card number and you get to auto top off you use 100 megabytes of data and it'll automatically take $15 out of your account. You have to be very fastidious with the account if you want to go with the free service. Additionally you have to make sure you use some data, make some calls and send some messages once a month or they deactivate your account. I suggest you go to their boards and do some searches about user satisfactions. Depending upon your phone or device call Quality varies widely. I bought a data card for a Nexus 7 2013 and for$30 I get two GB of data per month and 500 MB can be rolled over up to 10 gigabytes. You can't rollover all unused data. AT&T spend $30 a month and you can get 3 GB of data with no rollover and the quality is a bit better. I'm able to use a VOIP/SIP telephone app, called Talkatone that allows me to make a cell phone call over a data-only tablet. Of course it uses some data but it's actually quite manageable for occasional phone calls. Kurt #### billdz ##### Well-Known Member How much data and how many texts are used for tracking a few launches once or twice a month? That's all I'd use it for, my original plan was to use my son's card but a free SIM would be even better. And do you have to use some data, make some calls AND send some messages once a month to avoid deactivation? If yes, I'd need to remove the card from the tracker and put it into a phone to make a call. You are definitely right about the need to be "extremely careful" with FreedomPop. I see that you can't turn off auto top off unless you deposit at least$5. You have to pay $6 just to speak with a live CSR. And even if you select the free plan when you sign up, you are automatically enrolled in a premium plan and you have to log in and downgrade to get the free program. #### ksaves2 ##### Lifetime Supporter TRF Lifetime Supporter How much data and how many texts are used for tracking a few launches once or twice a month? That's all I'd use it for, my original plan was to use my son's card but a free SIM would be even better. And do you have to use some data, make some calls AND send some messages once a month to avoid deactivation? If yes, I'd need to remove the card from the tracker and put it into a phone to make a call. You are definitely right about the need to be "extremely careful" with FreedomPop. I see that you can't turn off auto top off unless you deposit at least$5. You have to pay $6 just to speak with a live CSR. And even if you select the free plan when you sign up, you are automatically enrolled in a premium plan and you have to log in and downgrade to get the free program. There is a "totally free" FAQ on their board that you should read closely and decide whether or not you want to chance it. You do get a month to decide. If you are just interested in SMS it could work out fine for you but you have to be certain you make some calls with it, send some messages with it and use a little bit of data. The call quality is very rough on the "free" service because you have to get on the "premium", additional cost plan for better call quality. FP has a tendency to "nickel and dime" you. Do a google search on the outfit and look at some of the d***ing videos out there. I currently have an AT&T card which incidentally comes with a phone number for some reason running in a Nexus 7 2012 3G. I need to pop it out and see if it works in my GSM cell phone.$30.00 and 3gb with no rollover. If it has better data quality, speed and VOIP/SIP usage, I might ditch FP and go with them.

If you follow the downgrading instructions on FP and shut off auto top off and use the SIM a few times a month you'll be fine as long as it works in your GSM/GPRS tracking device. It piggy-backs on the AT&T system.
That said, again look at their blog site and you'll see plenty of posts, "Why am I charged for this as I stopped that?"
I do have the free FP SIM in a dual SIM phone and use it to keep it active. If you don't use it for a month or two, they may shut it off. FP has a tendency to change their rules unnoticed so beware. Kurt

#### billdz

##### Well-Known Member
Thanks, you've talked me out of trying FP, guess there's no such thing as a free lunch.

I'm still trying to understand how these GPS trackers work.
1) Do they use data to receive the GPS info? My understanding is that, on a phone, GPS works independently of data and wifi, and data is only used to download maps, and there are no maps on the tracker.
2) Do they use data to transmit the GPS info from the tracker to my phone? Dugway mentioned a side-loaded app that needs to be loaded on the phone, perhaps the tracker uses data to send info to the app.
3) Or is the GPS info transmitted to my phone via SMS rather than data? I believe some trackers only send an SMS with the coordinates, which then must be entered into Google maps to find the tracker's location.

Anyhow, I'm assuming (and hoping) that, however the tracker works, it does not use a great amount of data or send a large number of SMS messages for a typical launch.

Thanks for any info,
Bill

#### ksaves2

Didn't mean to try to talk you out Bill. I do have an FP 4G Data only SIM in a Nexus 7 2013 with the 2GB "premium" plan for $30.00 a month because I like the rollover. I think they are misleading in their ads about rollover as one can only bank 500mb a month. Not the whole unused portion. I have the "Free" FP SIM in the second slot of a dual SIM phone and am going to continue to dink with it as I have it locked down. An alternative would be to just subscribe to a service when you need it. Perhaps others out there might know of some plans. I think you could pay for it monthly as you want it. If you find yourself needing to use it a lot, consider investing in a self-contained system. That is what I use. I only acquired the FP experience as I wanted to get Data into my Nexus tablets out in the field in case I didn't download a particular maptile off of Wifi for caching. As long as the launch site has cell phone service, I'd be in good stead. Kurt #### billdz ##### Well-Known Member I ordered one of the trackers in the link provided by Dugway and also a K8 GPS tracker from eBay, http://www.ebay.com/itm/K8-Mini-GPS...al-living-Locator-Alarm-Tracking/332218242434 The K8 arrived today but I have not been able to get it to work at all, tried both AT&T and MetroPCS simcards. Does not respond when I call the number and always shows as "offline" on the app. The instructions are in such bad English, it's possible I'm setting it up incorrectly, but I think it's just not working or is incompatible with these sim cards. Also tried the free FreedomPop sim, but FP uses AT&T, which has discontinued 2G service. MetroPCS uses T-Mobile, which still supports 2G, so not sure what the problem is. #### billdz ##### Well-Known Member It looks like I've found the problem. The ATT and FP sims don't work because ATT has discontinued 2G service completely, and this tracker (and the one suggested by Dugway) only works on 2G. MetroPCS works on T-Mobile, which still supports 2G, but MetroPCS "marries" the sim to a specific phone. I took the sim from the phone to which it was married, and thus it does not work in the tracker. Looks like I'll need a third sim card that runs on the T-Mobile network. Best deal I've seen so far is this$5 a month deal from Speedtalk:
In hindsight, it may have been better to buy a tracker that works on 3G (more expensive). But it is still doubtful whether the free FP sim will work with a tracker, as only "approved devices" work on FP.

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#### OverTheTop

##### Well-Known Member
TRF Supporter
I'm still trying to understand how these GPS trackers work.
The one I have pings you back with an sms containing the GPS location. You can set an interval to message you at. You can also just ring the number and it then rejects the call and sends the SMS. You then plug the number into another GPS or map program. There are some programs that automatically plot the data to a map. Never used them.

#### ksaves2

If I recall correctly, the 2G service is going to be cut out in the US eventually completely. Kurt

#### Dugway

##### Well-Known Member
There have been rumors of T-Mobile discontinuing 2G service for years. It could happen, but i'll believe it when I see it.

#### Dugway

The Android app I use is called 365GPS. There is one on the app store by that name, but it seems like it didn't work for me for some reason. It's been a number of months so I may be remembering incorrectly. I believe I sideloaded http://www.365gps.net/app/365gps.apk. I basically googled for "MD-601" and "365GPS" in order to find it. An app of that name is mentioned in the horrible documentation. I have no idea how the device communicates with my phone. My SIM card has 2GB of data per month for $10, and haven't had issues yet. Again, YMMV. #### billdz ##### Well-Known Member "My SIM card has 2GB of data per month for$10, and haven't had issues yet."
Thanks, Dugway. Which provider is your sim card? I'll guess T-Mobile or one of its MVNOs, since AT&T has discontinued its 2G service.

I was able to download 365GPS and I'll try it once the device arrives. Instead of this app, we can use any Android phone finder app to locate the rocket, or go to android.com/find on the web.