44 Rockwell Automation Publication 1756-UM542A-EN-P - September 2014
Appendix E GPS Antenna Cable Extensions
If the attenuation from a lower loss cable (such as LMR 600) is greater than 10
dB, you need to use an amplifier. Rockwell Automation does not supply
amplifiers. If you need an amplifier for your installation, follow the guidelines in
this appendix to specify and purchase an amplifier from a cable supplier.
Amplifiers of 15 and 30 dB gain are typically available.
Verify that the signal gain through the amplifier, minus the attenuation from the
c
able, is in the range of +10 dB (gain) to -10 dB (loss). Mount the amplifiers as
close to the antenna as possible without exposing them to the weather.
Example – Determining Cable Requirements
Cable length required is 30 m (100 ft).
From Ta b l e 5 on page
43, LMR-240 has a 9.7 dB loss that is acceptable, or
LMR-400 can be used with a 5 dB loss. Because LMR-400 cannot be connected
dir
ectly to the 1756HP-TIME module, a shorter length of RG58 can be used.
The antenna cable extension needs to connect to an SMA female connector on
t
he 1756HP-TIME module, and a TNC female connector on the antenna. So
the cable connectors need to be SMA male to TNC male.
Cable Extension Kits
The cable extension kits inTab l e 6 on page 45 can be purchased from Millimeter
Wave Technologies. For more information, visit the Millimeter Wave
T
echnologies website,
http://mmwavetech.com/, or call 1-480-941-2990.
LMR-400 and LMR-600 cables are too stiff and heavy to connect directly to the
small SMA connector on the 1756HP-TIME module.
For these cables, use a fly lead to wire the connector.
Amplifiers must pass the 3.3V DC supplied by the GPS receiver to power the
internal antenna amplifier, or provide the 3.3V DC internally.
If the amplifier blocks the DC component, it also needs to supply a dummy load
to prevent the receiver from giving a false No Antenna fault.
Rockwell Automation recommends a TNC bulkhead connector for cable-to-
cable connections.
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