Jam Immunity - ashtech DG16 Reference Manual

The DG16 provides the optional capabilities of 10 Hz or 20 Hz internal update
rates for position and raw data computations. When these options are installed,
the DG16 can output NMEA messages and raw data messages at intervals of 0.1
or 0.05 seconds (see Table 1.7 for a list of the available options). During periods in
which a 20 Hz update rate is not required, you can revert to a 10 Hz update rate
by issuing the command $PASHS,RCI for raw data and $PASHS,NME,PER for
NMEA messages.
When collecting data at 10 or 20 Hz, a 486-33 MHz or Pentium computer with a fast
serial and parallel port card (i.e., 16550 serial and parallel card) is required
because of large amounts of data being output through the serial ports. The serial
port baud rate should be set to 115200.
The DG16 provides jam immunity against in-band and out-of-band interferes.
For in-band interference, the DG16 can suppress in-band jamming signals while
maintaining signal tracking, horizontal accuracy and acquisition time
requirements. You can set the in-band jam immunity with the $PASHS,AJM,ON/
OFF command (default is OFF).
Out-of-band jam immunity is available all the time with no special settings
required.
The receiver normally computes and outputs positions in the WGS-84 coordinate
reference frame. However, it is possible to output positions in NMEA messages in
a number of different pre-defined datums, as well as in a user-defined datum.
To set the receiver to output positions in a different datum, use the $PASHS,DTM
command. Once set to a different datum, then all position outputs in NMEA
messages such as GGA and GLL and the position are referenced to the chosen
datum. For a list of Datums, see Table 6.15, "Predefined Datums and Associated
Reference Ellipsoids," on page 106.
If the list of datums does not include a datum of interest to the user, a user-defined
datum may be created and supplied to the receiver. This is done using the
Basic Operation
CAUTION
49