Saab R5 - Page 20

R5 SOLID AIS System
INSTALLATION
7000 118-200, C2 Page 20
high-power lines, such as radar or radio transmitter lines or the AIS VHF antenna
cable. A separation of 1 meter or more is recommended to avoid interference due to
RF-coupling. Crossing of antenna cables should be done at 90 degrees to minimise
magnetic field coupling.
The table below gives recommendation on cables that can be used for the
Transponder GPS-antenna connections, the cables used should always be of marine
approved type. Due to the high frequency it’s important that the attenuation in the cable
is low for the specific frequency (1.5 GHz).
Type
Attenuation @ 1.5
GHz (dB/m)
 (mm)
Weight (kg/100m)
RG 58
0.9
5
3.7
RG 400
0.6
4.95
6.3
RG 223
0.6
5.40
5.5
RG 214
0.35
10.8
18.5
RG 225
0.3
10.9
23.3
Table 5 – GPS Antenna Cables
For optimum performance approximately +10dB gain should be available when the
cable attenuation has been subtracted from the GPS-antenna preamplifier gain. The
net gain shall not exceed +26dB.
Example:
Cable type
Preamplifier
gain (dB)
Required min cable
length (m)
Recommended
max. cable length
(m)
RG 58
12
0
2
RG 58
26
0
18
RG 58
30
4.5
22
RG 223
12
0
3.5
RG 223
26
0
26.5
RG 223
30
6.5
33.5
RG 214
12
0
6
RG 214
26
0
46
RG 214
30
11.5
57
Table 6 – GPS Antenna Cable Examples