WX16 User Manual | 64
7.5.4 Coax
Cables
If a coax cable connects to the antenna via connectors, it is very important to
weatherproof the connection using our 1000-2314 or equivalent sealing tape. Moisture
ingress into a coax cable connection is the most common cause of problems with
antenna installations. A three layer sealing process is recommended – an initial layer
of electrical PVC tape, followed by a second layer of self-vulcanizing weatherproofing
tape (1000-2314), with a final layer of electrical PVC tape.
Allowing a drip “U loop” of cable before the connection is also a good idea. The loop
allows water to drip off the bottom of the U instead of into the connection, reduces
installation strain and provides spare cable length in case later the original connectors
need to be removed, the cable cut back and new connectors fitted.
Avoid installing coax cables together in long parallel paths. Leakage from one cable to
another has a similar effect as mounting an antenna near another antenna.
7.6
Surge Protection & Grounding
Voltage surges can enter the WX16 via the antenna connection, power supply
connection, connections to other equipment and even the “earth” or “ground”
connection. Surges are electrical energy following a path to earth, and the best
protection is achieved by “draining” the surge energy to earth via an alternate path.
Wireless devices need to have a solid connection to earth via a ground stake or ground
grid if the soil has poor conductivity. Solid connection means a large capacity
conductor (not a small wire) with no coils or sharp bends. All other devices connected
to the WX16 need to be grounded to the same ground point. There can be significant
resistance between different ground points leading to very large voltage differences
during lightning activity. As many wireless units are damaged by earth potential surges
due to incorrect grounding as are damaged bydirect surge voltage.
It is very difficult to protect against direct lightning strikes, but the probability of a direct
strike at any one location is very small. Unfortunately, power line surges and
electromagnetic energy in the air can induce high voltage surges from lightning activity
several miles away.
7.6.1 Antenna
Grounding
Electromagnetic energy in the air will be drained to ground via any and every earth
path. An earth path exists between the antenna and the WX16, and to protect against
damage, this earth path current must be kept as small as possible. This is achieved by
providing better alternate earth paths. It is important to ground the antenna to the same
ground point as the WX16. Antennas are normally mounted to a metal bracket that
should be grounded to the WX16 earth connection. Surge energy induced into the
antenna will be drained first by the mount’s ground connection, second by the outside
shield of the coax cable to the ground connection on the radio and third by the internal
conductor of the coax cable via the radio electronics. This third earth path causes
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