GPS has various functions which are applicable to communications projects. The primary cost item is the receiver and active antenna. Two things I have always looked for in a GPS module is NMEA data string and the 1 pulse per second output.
You can decode the NMEA string for location and time (field tracking, etc.) and/or you can use the 1 pps output to lock your local frequency counter and standard.
Many surplus 12 ch gps receivers have these outputs and can be found on the market. If you search the web you will find numerous DIY projects using the NMEA and the 1 pps outputs. I have also found the low cost handheld TREK GPS units in sporting stores for under $100 have the NMEA output, but the 1 pps is not available on them without doing internal surgery.
The full NMEA specification and protocol is available on the web. Two things one must remember when using these receivers. The location (+/-) is the location of the antenna and if you are forwarding the data to another location then you will have a timing and turn around error due to the transmission length and if other activity is on the same wireless channel. Tree cover will affect the accuracy and limestone cliffs are really bad on tracking. GPS does not work inside of a building you need a clear line of sight with the satellites.
I would be very interested in what others are doing with a GPS receiver and a PICAXE chip.
I am currently working on being able to track low cost wireless sensors and plan on using the 1 pps output to sync my transmissions.
Stan AK0B
You can decode the NMEA string for location and time (field tracking, etc.) and/or you can use the 1 pps output to lock your local frequency counter and standard.
Many surplus 12 ch gps receivers have these outputs and can be found on the market. If you search the web you will find numerous DIY projects using the NMEA and the 1 pps outputs. I have also found the low cost handheld TREK GPS units in sporting stores for under $100 have the NMEA output, but the 1 pps is not available on them without doing internal surgery.
The full NMEA specification and protocol is available on the web. Two things one must remember when using these receivers. The location (+/-) is the location of the antenna and if you are forwarding the data to another location then you will have a timing and turn around error due to the transmission length and if other activity is on the same wireless channel. Tree cover will affect the accuracy and limestone cliffs are really bad on tracking. GPS does not work inside of a building you need a clear line of sight with the satellites.
I would be very interested in what others are doing with a GPS receiver and a PICAXE chip.
I am currently working on being able to track low cost wireless sensors and plan on using the 1 pps output to sync my transmissions.
Stan AK0B