GPS frequencies

The data signal, with a bit rate of 50 bit/s and a frame period of 30 s, is being transmitted on two frequencies at the same time, using a spread spectrum method:

L1 (1575 MHz)

The C/A code for civil use and the not poblicly known P/Y code for military use are being deployed on this frequency. The transmitted data signal is identical on both code sequences and constitues the 1500 bit long navigation message. The message needs half a minute to be transmitted and contains every important information on the satelite, such as date, identification number, corrections, orbit, but also the condition of the satelite. GPS receivers normally buffer these data. For the device initialisation, also the almanac data, which contain the rough orbiting data of all stelites, are being transmitted. The transmission takes about 12 minutes.

L2 (1227 MHz)

The second frequency transmits the P/Y code only. This frequency may solely be used for military purposes. By transmitting on two frequencies, the data accuracy can be improved.

L5 (1176 MHz)

This new frequency is supposed to further increase the stability of the reception and is intended for aviation and rescue service applications. It is still under construction.