This thread is the follow on to my original DIY Smartphone GPS Tracker.
I've been working on an open source GPS tracker that uses a smartphone as the display. The system consists of three components:

1. GPS transmitter
2. Receiver KY32-SI5110-F-BC (data sheet: http://www.kynix.com/uploadfiles/p [...] 0-F-BC.pdf )
3. Android smartphone with the correct app

Complete System:

Click image for larger version.

Name: rocket track system small.jpg
Views: 1448
Size: 78.4 KB
ID: 127066

(Sorry for the lousy pic. When I build another rx I'll take some better shots!)

Finished transmitter and the bare PCB:

Click image for larger version.

Name: Rocket_Track_Tx_v10.JPG
Views: 845
Size: 83.4 KB
ID: 127006

The idea is to use a simple, inexpensive, unlicensed radio link between the rocket and a base station. The GPS receiver in the rocket sends the current position over the radio link to the base station, which in turn relays the data to a smartphone for display. The simplest, most universal interface for external devices available on smartphones is Bluetooth. Therefore the base station actually consists of two transceivers, one for the air link to the rocket and a Bluetooth slave that connects to the smartphone. By disabling the GPS in the phone and using the GPS data from the rocket, apps like Google maps display the rocket's position on the map, not the smartphone's! Both the transmitter and the base station run off a single cell Lipo battery. The base station includes a Lipo charger powered from a micro USB connector so you can easily charge the batteries in the field using your cell phone charger.

Only Android is supported because iOS devices have stupid rules prohibiting connecting to "unsigned" Bluetooth devices.

System Components

GPS transmitter:

Click image for larger version.

Name: Rocket_Track_Txs_v10_small.jpg
Views: 945
Size: 65.7 KB
ID: 127120

Base station receiver with Bluetooth interface:

Pic coming soon!

Motivation:

I don't really need a tracker where I fly, but I like gadgets and a GPS tracker definitely qualifies as a neat gadget. However I have no desire to get a ham license and the $400+ radio and equiptment to use a licensed tracker, especially since I already own a vastly more capable device. The goal is to make this small, simple and most importantly, cheap!

The system is based on the XBee Pro 900HP radio modules. In the US, It operates on the unlicensed 915 MHz ISM band. The maximum output power of the transceiver is 250 mW.

Questions:

1. Does it work?

Yes. It works great!

2. What is the range?

Miles in the air. Realisticaly less than a mile on the ground. The radio modules have the ability to connect to each other in a mesh network so the range can be extended quite far.

3. Does it work with my iPhone?

No. Apple doesn't allow your iPhone to connect any old Bluetooth device. Manufacturers must comply with their rules and pay a fee to get a key to allow the device to connect. I'm not doing that. If you really want to use this but don't want to give up your iPhone, buy a Nexus 7.

4. Do I need cell coverage at the field?

No. This tracker will work with phones or tablets without cellular coverage or plans. However, if you want to actually see where your rocket is on a map, you need to save an offline version of the map beforehand.

5. Are the any restrictions on its use?

In the US, not that I'm aware of. The radio operates in the unlicensed 915 MHz ISM band and is under the power limits for this band. It does not use cell phones or the cellular network to transmit the position. If you don't reside in the US, you need to purchase the XBee modules licensed for use in your country.

6. Are you going to make it better?

Yep, that is the plan. Future versions may include features like an altimeter, accelerometer and logging.

7. Are you going to sell the tracker?

Assembled systems, no. However I do have PCBs available for sale. Transmitter is $10, receiver is $20, set is $27, shipping to CONUS included. PM me if you are interested.

Transmitter PCB:

Click image for larger version.

Name: Rocket Track TX 1.0.JPG
Views: 583
Size: 124.6 KB
ID: 128425

Receiver PCB:

Click image for larger version.

Name: Rocket Track RX 1.1.jpg
Views: 481
Size: 72.9 KB
ID: 128959

8. $27 for a couple of PCBs! What a ripoff! Why so much?

No one is forcing you to buy from me. Grab the files and send them to your favorite PCB board shop. Although I'd be surprised if you ended up spending less than $27. Please let me know if you find a cheaper board shop!

9. Are you going to release the plans?

Yes! Everything you need to reproduce this tracker for yourself is included in this thread, including the PCB fab files.

10. The Bluetooth base station seems like a stupid hack. Why not just use Bluetooth (or Wifi) in the rocket?

Bluetooth doesn't have the range that these radios have, and Wifi requires more complex electronics in the rocket. Additionally, Android already has the ability to use an external Bluetooth GPS so all the existing map apps just work.

Each of the components are detailed in following posts. Please feel free to post any questions, comments, improvements, etc. in this thread.