Vector Sensor Reference Manual 39
Caution - Thread the mount into the mount hand-tight only. Damage resulting from
over-tightening the antenna is not covered by warranty.
2.7.3 Routing and Securing the Antenna Cable
The two CDA-RTK antennas that come preinstalled on the bracket of the Antenna Array each
require a 50 Ω impedance antenna extension cable such as RG-58U (up to a maximum of 15 m
(49 ft) in length) for proper operation.
The GPS engines inside the Vector Sensor require a minimum input gain of 10 dB (and maximum
of 40 dB before saturation will occur). The CDA-RTK antennas offer 28 dB of gain, so the loss
budget to accommodate for cable losses is 18 dB. Regardless of the cable material and length that
you choose, you must ensure that cable losses are less than 18 dB of attenuation. Due to
variances in the CDA-RTK gain and practical attenuation of cable materials and connectors, it’s a
good idea to reduce this budget to 15 dB. This budget of 15 dB is present to overcome the
resulting attenuation of an RF cable.
When deciding on an antenna location, consider the amount of cable required. Keep in mind that
a longer cable of the same material will result in a higher loss than a shorter one. If the overall loss
of the longer cable exceeds 15 dB, the cable material will need to be changed. This normally
means a more expensive material that has a larger diameter and less flexibility. The standard cables
that come with the Vector Sensor are an RG58 material family. Their attenuation is approximately
0.8 dB/m. Including connector losses, the nominal loss of these RF cables is approximately 10 dB,
which is within the tolerable loss budget. If a 15 m or 20 m cable run is required, an RG8 variety
is available from CSI Wireless. Longer lengths than 20 m is required, more sophisticated materials
will be required.
For more information on cable length or low-loss cable, please contact your CSI Wireless dealer
or CSI Wireless Technical Support. The following is a short summary of other readily available
cable materials that have 50 Ω impedance. Cable loss cited below does not include any connector
losses.
Material Loss at GPS L1 (1.575 GHz)
RG58 0.78 dB / m
RG8 0.36 dB / m
Times Microwave LMR400 0.15 dB / m
When choosing a route for the antenna extension cable:
• Avoid running cables in areas of excessive heat.
• Keep antenna cables away from corrosive chemicals.
• Do not run the extension cable through door or window jams.
• Keep the antenna cable away from rotating machinery.
• Do not bend excessively or crimp the antenna extension cable.
• Avoid placing tension on the cable.
• Remove unwanted slack from the antenna extension cable at the receiver end.
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