Arbiter Systems 1201B, Operation Manuals

Page: 37 / 228

4.4 Technical Details of GNSS Antennas and Cables 19
delay has upon GNSS timing accuracy. Cable delay is calculated from the velocity factor and
physical length of the cable. Antenna group delay is fixed at 40 nanoseconds, and is contributed
by the GNSS antenna itself. During the initial factory calibration of the clock, this combined value
called System Delay is entered into the clock memory.
The delay for a standard, 15-meter RG-6 cable is 60 nanoseconds. For other cable assemblies
supplied by Arbiter Systems, the delay is tabulated in Table 4.2 below. For cable assemblies not
found in Table 4.2, use Equation 4.1 for calculating cable delay. For other lengths and types of
cables, remember to add 40 ns to your cable delay and enter that value into the clock.
P/N Description Delay, ns Signal Level, dB
CA0021315 15 m (50 ft) cable, RG-6 60 ns -5 dB
CA0021330 30 m (100 ft) cable, RG-6 119 ns -9 dB
CA0021345 45 m (150 ft) cable, RG-6 177 ns -13 dB
CA0021360 60 m (200 ft) cable, RG-6 236 ns -17 dB
CA0021375 75 m (250 ft) cable, RG-6 295 ns -21 dB
WC0004900 305 m (1000 ft) roll RG-11 3.92 ns/m -17.5 dB/100 m
TF0006400 RG-6 Crimp Tool N/A N/A
TF0006000 RG-11 Crimp Tool N/A N/A
TF0013200 RG-6 Cable Stripping Tool N/A N/A
TF0013300 RG-11 Cable Stripping Tool N/A N/A
AS0044800 RG-11 crimp tool and 25 connectors N/A N/A
AS0044700 21 dB in-line amplifier 1 ns +21 dB
Table 4.2: GNSS Cable Data and Accessory Information
(4.1) T = λ
1
CKv
Where:
T = Cable delay, in nanoseconds;
λ = Cable length, in meters;
C = Speed of light (3
×
10
8
meters per second);
Kv = Nominal velocity of propagation (0.85 for RG-6).
Attenuation
Attenuation depends upon the cable length, and the loss per unit length. The total attenuation
must be limited to 21 dB (maximum) at the GNSS L1 frequency of 1575.42 MHz. Loss up to 42 dB
can be accommodated with the separately available 21 dB in-line preamplifier (P/N AS0044700).