Rockwell Automation Publication 1756-UM542A-EN-P - September 2014 43
Appendix E
GPS Antenna Cable Extensions
Cable Extensions
The 1756HP-TIME module ships with a 5 m (16 ft) RG58 coaxial cable.
Rockwell Automation does not supply longer cables. If you need a longer cable
for your installation, follow the guidelines in this appendix to specify and
purchase extensions from a cable supplier.
Determine the Length of the Cable
Determine the length of the cable by measuring the cable path from the
1756HP-TIME module to a position that provides the antenna with a 360
degree clear view of the sky. Plan your installation so the length of the cable path
is as short as possible.
Determine the Attenuation Rate of the Cable
Determine the type and quality of cable and whether an amplifier is required. Use
the cable attenuation tables of the manufacture. Determine the over-signal
attenuation at 1.5 GHz. Keep the attenuation below 10 dB. Rockwell
Automation recommends no more than 6 dB for better performance.
Table
5 provides typical attenuation values (in dB) for common types of 50 Ω
coaxial cable at 1.5 GHz. Light green shading shows acceptable levels of
atten
uation below 10 dB. Dark green shading is in the recommended range.
Table 5 - - Typical Attenuation Values in dB for Cable Extension, m (ft)
Topic Page
Cable Extensions 43
Lightning Protection Devices 45
5
(16)
10
(33)
15
(49)
20
(66)
25
(82)
30
(98)
35
(115)
40
(131)
45
(148)
50
(164)
55
(180)
60
(197)
65
(213)
70
(230)
75
(246)
80
(262)
85
(279)
90
(295)
95
(312)
100
(328)
Cable Type Typical Attenuation Values in dB
RG58 3.1 6.3 9.4 12.5 15.7 18.8 21.9 25.0 28.2 31.3 34.4 37.6 40.7 43.8 47.0 50.1 53.2 56.3 59.5 62.6
LMR-240 1.6 3.2 4.9 6.5 8.1 9.7 11.3 13.0 14.6 16.2 17.8 19.4 21.0 22.7 24.3 25.9 27.5 29.1 30.8 32.4
LMR-400 0.8 1.7 2.5 3.4 4.2 5.0 5.9 6.7 7.6 8.4 9.2 10.1 10.9 11.8 12.6 13.5 14.3 15.1 16.0 16.8
LMR-600 0.5 1.1 1.6 2.2 2.7 3.3 3.8 4.4 4.9 5.4 6.0 6.5 7.1 7.6 8.2 8.7 9.2 9.8 10.3 10.9
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