User Manual

42 MHX-920 Operating Manual: Chapter 5 Installation
The installation, removal or
maintenance of all antenna
components must be carried out
by qualified and experienced
personnel.
Never work on an antenna system
when there is lightning in the
area.
Direct human contact with the
antenna is potentially unhealthy
when the MHX-920 is generating
RF energy. Always ensure that
the MHX-920 equipment is
powered down during installation.
5.2.2 Installing External Cables, Antennas and Lightning
Arrestors
The installation, removal or maintenance of all antenna components must be
carried out by qualified and experienced personnel.
Never work on an antenna system when there is lightning in the area.
Direct human contact with the antenna is potentially unhealthy when the
MHX-920 is generating RF energy. Always ensure that the MHX-920
equipment is powered down during installation.
Surge Arrestors
The most effective protection against lightning is to install two lightning
(surge) arrestors. One at the antenna, and the other at the interface with the
equipment. The surge arrestor grounding system should be fully
interconnected with the transmission tower and power grounding systems to
form a single, fully integrated ground circuit. Typically, both ports on surge
arrestors are N-female.
Cabling
The following coax cables are recommended:
Cable Loss (dB/100ft)
LMR 195 10.7
LMR 400 3.9
LMR 600 2.5
Factors to take into consideration when choosing a cable are:
• price;
• bend radius limitations (the lower performance cables generally can
bend more sharply)
• performance requirements; and,
• distance between the equipment and the antenna.
When installing the cable, always begin fastening at the top near the antenna
connector/surge arrestor. The cable must be supported at the top with a
hose clamp or wrap lock, and at 5 ft intervals down the length of the tower.
Over-tightening the fasteners will dent the cable and reduce performance. If
properly grounded surge arrestors are not installed at both the top and the
bottom of the cable, then the cable should be grounded to the tower at these
locations using a cable grounding kit. If the tower is non-conductive, then a
separate conductor, physically separate from the cable, should be run down
the tower.