L2 Tracking Control

GPS satellites transmit several different carrier frequencies and apply different modulation codes to those carriers. The NetRS is capable of tracking several kinds of codes. On the L1 frequency (~1575 MHz) the C/A-code is always tracked. On the L2 frequency (~1255MHz), two codes may be available. On older satellites, the encrypted Y-code is usually all that is available. This signal was designed for military users and cannot be tracked directly without using militarized equipment. The NetRS normally uses a Trimble-proprietary cross-correlation method to track these Y-code signals.

Newer GPS satellites may modulate the L2 frequency with a second code designed for civilian use. This is the L2 Civil Signal, often refered to as L2C or sometimes L2CS. The NetRS is able to track L2C signals when they are available. Note that the first L2C-capable satellite was launched in late 2005, and it will take some time before a significant number of other L2C-capable signals are available. As of this writing (March 2006) only PRN 17 is transmitting L2C.

You can choose which signals your NetRS will attempt to track on the L2 channels by using the L2 Tracking Control page. There are four modes available which affect tracking on all GPS satellites.

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