16
GNSS Antenna and Cable Information
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
CA0021302
2 m (6 ft) cable, RG-6
8 ns
-2 dB
CA0021306
6 m (20 ft) cable, RG-6
24 ns
-3 dB
CA0021315
15 m (50 ft) cable, RG-6
60 ns
-5 dB
CA0021330
30 m (100 ft) cable, RG-6
118 ns
-9 dB
CA0021345
45 m (150 ft) cable, RG-6
177 ns
-13 dB
CA0021350
50 m (164 ft) cable, RG-6
196 ns
-14 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
3.924 ns/m
-17.5 dB/100 m
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.
DC Resistance
The cross-sectional area and length of the conductors in the cable determine the dc resistance.
Since power to the RF preamplifier in the antenna, and possible inline amplifier, is supplied via the
antenna cable, excessive dc resistance will degrade performance.
Available Antenna Cables and Accessories for Longer Runs
Longer antenna cables are available. Unbroken RG-6 cable lengths up to 100 m (328 ft) are available.
Not long enough? A 21 dB in-line preamplifier allows for a adding up to another 75 m (250 ft) for a
total combined length up to 175 m (574 ft). Still not long enough? Another option is RG-11 cable
which allows for an unbroken length up to 195 m (640 ft) or up to 315 m (1033 ft) with the 21 dB
in-line preamplifier.
