World Time Solutions GPS6000-PRO User Manual - page 10
GPS6000-PRO - GPS Time Receiver - User Manual - Version 1.1
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Section 3: Installing the GPS6000-PRO
3.5 - The cable delay offset
The GPS6000-PRO is capable of providing time data accurate to
within 30 nsec of UTC. At this level of accuracy, taking account of
cable lengths becomes critical. Every metre of cable between the
GNSS antenna and your time server causes an additional error of
approximately 5 nsec (see note over page). For long cable lengths,
this accumulated error can become very significant.
The cable delay offset provides a simple solution to correct for errors
due to cable propagation delays. The total cable length between the
GNSS antenna and your time server is entered using the switch bank.
The GNSS decoder then automatically advances the time data by the
required offset to correct for the cable propagation delay.
GPS6000-PRO systems are supplied with the correct cable delay
offset value pre-programmed. For a typical installation, this preset
value should not need any adjustment. However, if required, the
cable delay offset can be programmed using the following guidelines.
3.5.1 - Programming the cable delay offset
PLEASE NOTE: THE PRESET CABLE DELAY OFFSET SHOULD
NOT NORMALLY REQUIRE ANY ADJUSTMENT.
The cable delay offset is programmed in metres using the cable
delay offset switch bank. The total cable length (in metres) should be
encoded in an 8 bit binary format and entered into the switch bank.
Switches set to on (the upper position) are summed. As shown in
figure 3.4 below, the left-hand switch is the most significant bit (128m)
and the right-hand switch the least significant digit (1m).
Figure 3.4 - The cable delay offset switch bank
ANTENNA
STATUS
GPS6000 - GNSS TIME DECODER
CABLE DELAY OFFSET
add 1m to cable length
add 2m to cable length
add 4m to cable length
add 8m to cable length
add 16m to cable length
add 32m to cable length
add 64m to cable length
add 128m to cable length