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Commands
4.2.7
PLLBANDWIDTH Set the phase lock loop bandwidth
Depending upon the environment, it may be beneficial to change the Phase Lock Loop (PLL)
bandwidths. The default bandwidth of the GPStation-6 is 10Hz, however tracking performance in
certain scintillation environments may be improved by changing this bandwidth. This command also
allows the default channel aiding to be changed for secondary signal tracking loops. Issuing this
command will cause all affected channels to reset lock as they re-initialize their tracking loops.
There are some considerations when using this command:
•
Lower bandwidths impedes the ability of the feedback loop to track step functions, resulting
in more "hang-off" phase errors in the measurements. Step functions can occur in the phase
when the clock frequency has small jumps or "pops" that the PLL needs to react to. The
GPStation-6 uses a low noise OCXO to minimize these jumps, but in extreme cases clock
frequency "pop" could cause extra losses of lock in lower bandwidth PLLs.
•
Changing the bandwidth will change the overall phase noise of the ADR measurements.
Generally, the higher the bandwidth, the noisier the ADR measurements, but the more robust
the tracking loop.
•
By default, all secondary signals except GPSL2P(Y) are tracked independently on the
GPStation-6. It is recommended that this setting not be changed for ionospheric monitoring
applications.
Abbreviated ASCII Syntax:
PLLBANDWIDTH signal_type bandwidth [aiding]
Input Example:
pllbandwidth gpsl1ca 15.0
Field
Field Type
1
PLLBANDWIDTH
Header
2
Signal type
3
PLL bandwidth
4
PLL aiding
parameter
GPStation-6 User Manual Rev 2
ASCII
Binary
Value
Value
-
-
This field contains the
command name or the
message header
depending on whether
the command is
abbreviated ASCII,
ASCII or binary,
respectively
Signal type to
configure (refer to
Table 11, Signal
Type)
Phase lock loop
bandwidth, units Hz
Secondary channel
phase lock loop aiding
parameter (Default =
PLLAIDING_CURRE
NT) (refer to Table 13,
PLL Aiding
Parameters)
Binary
Description
Format
-
ENUM
FLOAT
ENUM
Message ID: 687
Binary
Binary
Bytes
Offset
H
0
4
H
4
H+4
4
H+8
54
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