Chapter 8 215
GPS Modulation (Option 409)
Real Time GPS
User Files
You can create data files internally in the PSG or create them externally and download them to the PSG. In
either case, the size of user data files is limited by the amount of available PSG memory. If you develop data
files externally, you can define signal structures that are not available internally in the PSG. For example, if
you require a fully-coded signal consisting of frames structured according to GPS standards (1 frame
consisting of 5 subframes and 25 pages), you can develop this signal externally and download it to the PSG.
User files can be in either binary or bit format. Save user files to the bin directory.
Select a data mode for your data file as you would for other data types (see “Data Modes and Subframe
Structures” on page 212). If files are created externally and incorporate parity bits, use the Raw data mode to
transmit the data in its original form. If your file does not contain parity bits and you want to incorporate
parity bits in the transmitted signal, select the encoded (Enc) data mode. The PSG will compute parity bits
for the last 6-bits of each word.
NOTE If you select the encoded mode for a user file that incorporates parity bits, the parity bits
will be recomputed and their values changed.
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