Jackson Labs Mini-JLT GNSS, Руководство пользователя

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© 2017 Jackson Labs Technologies, Inc. 9
Mini-JLT GNSS™
User Manual
Loop parameters are optimized for the TCXO on the board, and changing the factory settings may
result in the unit’s performance to deteriorate.
The commands to control the loop parameters are part of the servo? command. See also the
SERVO
Subsystem section below.
The individual commands are:
EFC Scale: this is the proportional gain of the PID loop. Higher values will give quicker
convergence, and faster locking of the GPS time (lower loop time constant), lower values give less
noise. Values between 0.7 (good double oven OCXO) and 6.0 (simple single-oven OCXO) are
typical.
EFC Damping: overall IIR filter time constant. higher values increase loop time
constant. Jackson Labs Technologies, Inc. typically uses values between 10 to 50. Setting this value
too high may cause loop instability.
Phase compensation: this is the Integral part of the PID loop. This corrects phase offsets between
the Mini-JLT GNSS™ 1PPS signal and the UTC 1PPS signal as generated by the GNSS receiver. Set
higher values for tighter phase-following at the expense of frequency stability. Typical values range
from 4 - 30, 25 being the default. Setting this value too high may cause loop instability.
A well-compensated unit will show performance similar to the plot shown in
Figure 2.3 when
experiencing small perturbations: