HBM Genesis GEN5i User Manual page 210

210
B Lightning considerations
Locate the antenna at least 15 meters away from lightning rods, towers, or
structures that attract lightning. GPS antenna damage is usually not the
result of a direct lightning strike, but the effects of a lightning strike on a
nearby structure. Locate the GPS antenna lower than any structures that
may attract a strike.
C Maintenance considerations
If the GPS antenna fails or must be checked, having the antenna positioned
in an accessible location will facilitate maintenance. Avoid installing the
antenna on a tower, which requires a specialist to maintain.
D Interference consideration
Avoid the direct radiation from transmitting antennas (such as TV or
Cellular).
Rule 2. Is a GPS line amplifier needed?
A Cable length
Add up the total length of all the cables for the installation. If the total cable
length is 150 ft or less, no amplifier is needed. If the total length is between
150 ft and 300 ft, a line amplifier is required. For lengths greater than
300 ft, contact Symmetricom for further assistance.
B Placement
Mount line amplifiers as close to the antenna as possible. Connect the
amplifier directly to the antenna. The line amplifiers fit nicely inside the
antenna mast where they are protected from the weather.
Rule 3: Lightning arrestors
A Is a lightning arrestor needed?
Very probably, yes. Lightning does not have to strike the antenna to
significantly damage the antenna and GPS receiver. Lightning strikes
induce damaging voltages in the antenna system when striking nearby
objects.
B What do I need?
A commonly used configuration is to place a lightning arrestor where the
antenna cable enters the building (either inside or outside), because there
is often a good earth ground nearby to connect to. If the cable between this
lightning arrestor and the GPS receiver is longer than four meters, it is good
practice to place a second lightning arrestor within four meters of the GPS
receiver. The second arrestor reduces any lightning-induced voltages in
the cable to the receiver.
C Grounding
The lightning arrestor does not need a grounding strap if it is directly bolted
to a grounding plate. A grounding strap should be used if you cannot
connect directly to a grounding plate.
D Caution
If you are not comfortable designing your own lightning protection system,
seek professional assistance. This is only a guide.
GEN5i
I2679-4.0 en