EndRun Sonoma N12, User Manual

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S o n o m a U s e r M a n u a l 132
A P P E N D I X E
133 S o n o m a U s e r M a n u a l
I N S T A L L I N G T H E G P S A N T E N N A
1. The splitter must be DC-blocked on one leg. The GPS Receivers in both time servers output
5 VDC up the coax to power the GPS antenna’s built-in preamp. You must not connect these two
power sources together.
2. It is desirable that the DC-blocked leg has a DC load resistor to simulate a GPS antenna load.
This way you will not get a false alarm from the GPS Receiver’s antenna load sensor. However, the
Sonoma time server allows you to mask an antenna fault alarm from causing a system fault by using
the
setantfltmask
command. See details in
Chapter 9 - Console Port Control and Status
.
3. The signal splitter supplied by EndRun has a built-in preamplifier to compensate for signal loss
through the splitter. If using a splitter other than the one supplied by EndRun you may need to com-
pensate for splitter signal loss by using a separate GPS preamplifier.
Calibrate Your Receiver
If your Sonoma is operating with the Precision Time Protocol (PTP), then you may wish to calibrate
your GPS receiver for maximum timing accuracy. In order for the Sonoma to synchronize with
maximum accuracy to UTC, the delay for the cable and all devices between the antenna and the GPS
receiver input (i.e. GPS preamplifiers, signal splitters, lightning arrestors, etc.) must be compensated
for. You can do this via the keypad/display (see Chapter 11 - Front-Panel Keypad/Display, Re-
ceiver: Calibrate
) or via the console port
caldelay
and
setcaldelay
commands (see
Chapter 9
- Console Port Control & Status) .
Calibration is used to compensate for the propagation delay between the GPS antenna and the So-
noma GPS receiver input connector. Positive values remove delay by advancing Sonoma’s 1 PPS
on-time reference by the specified number of nanoseconds. Negative values add delay by retarding
the 1 PPS and are used in special circumstances. The calibration value is determined by summing all
the delays.
The calibration range is ±500,000 nanoseconds. The default value as shipped from the factory is 0.
The table below lists nominal propagation delays for the GPS cable and accessories supplied by
EndRun Technologies. For the most demanding timing applications, it is recommended that the delay
between the antenna and Sonoma receiver input be precisely measured.