Spectracom GSG-5 series, Руководство пользователя с руководством по SCPI

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1.
Enable L1 C/A, L1P, and L2P only:
The L1P and L2P will be transmitted without encryption.
2.
Enable L1 C/A, L1P, and L2P, and Pseudo P(Y):
The P code will be scrambled to mimic a realistic P(Y) signal for use in receivers
that can make use of L1/L2 P(Y) signals for codeless applications, or to provide a
signal in the band to better emulate the real world.
In the GSG-6 series, the NAV message transmitted by the GPS satellites is updated
to reflect if (pseudo-) encryption is active or not. This is specified by bit 19 in the
second word of subframe one. This bit represents the anti-spoof (A-S) flag, where
“1” indicates that the A-S mode is on in that satellite. It is recommended to enable
Pseudo P(Y) when the GSG-unit supports it. This will set the A-S flag to ON which
is required in some receivers. GPS receivers may reject L1CA code if the A-S flag
is off.
In GSG-5x units, where it is not possible to transmit Pseudo P(Y), the A-S bit is
always set to ON to indicate that encryption is on (although the actual RF signal is
not transmitted on such units).
The NAV message also holds information on the type of L2 signal being trans
mitted (bits 11 and 12 of word three in subframe one). These bits are always set
to indicate that the P code is active on L2.
3.5.10.6 SBAS Satellites
Several GNSS augmentation systems, e.g., differential GPS, exist to further improve pos
itioning, navigation, and timing functionality (see also:
www.gps.gov
). Space Based Aug
mentation Systems (SBAS) incorporate system components such as additional SBAS geo
satellites, ground reference stations, and user equipment which together aid the GPS system,
thereby allowing greater precision and integrity, among other things.
SBAS systems support specific GNSS systems, are available for civil use, and have been/are
being developed for all of the GNSS systems worldwide:
Figure 3-23:
GNSS SBAS systems
3.5 "Select" Menu
CHAPTER
3
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