The following modules are known to work with the kit. The table gives a source if known, and the appropriate "GPS Baud" setting to use in the kit, to suit the GPS module's default output configuration with the kit.

Please note that some inexpensive GPS modules such as the VK16E using the Sirf III chipset, have a somewhat inaccurate 1pps signal. A method to cope with this has been devised and released in firmware version v3.01. Using the new method, the calibration accuracy is very good. You can read more details here.

Model Antenna Source "GPS Baud" Comments
SKM61 Built-in AVAILABLE FROM QRP Labs! 009,600 Uses 5V supply. Requires two 4.7K pullup resistors. Extremely good sensitivity and highly accurate (10ns) timing pulse.
SKM52 Built-in Data here, used to be available from QRP Labs 009,600 Requires 3.3V supply, and 10K pullup resistors. Very good sensitivity and highly accurate (10ns) timing pulse.
VK16E Built-in Data here, used to be available from QRP Labs 009,600 See HP calibration comments.
Trimble Silvana ACM Built-in dpieshop 009,600 Uses Trimble Condor C1919A GPS module; requires 3.3V regulated supply.
Works only with v2.03 and above.
MTK3339 Built-in Adafruit 009,600  
Reyax UP501 Built-in eBay, GBP 17 009,600 Requires 3.3V supply. Note different "GPS Baud" setting. Do NOT use pull-up resistors!
EM-406A Built-in Sparkfun or Expansys or Proto-pic 004,800 Works with firmware v2.03 and above.
May need to use 10K pull-up resistors from 1pps and Serial signal to +5V