User's Manual

Exalt Communications, Inc.

EX-5r Installation & Management

5000007 24

2006-05-17

4.3.2 Transmission Line from Antenna to Radio

For the external antenna version, most installations use coaxial transmission line for the

connection between the antenna and the radio device. In typical EX-5r installations, this coaxial

transmission line is very short, and may not require or benefit from RF lightning protection.

However, a properly grounded RF lightning protection device is recommended, where necessary,

and is highly recommended when the RF cable length exceeds 10 feet.

Coaxial transmission line may be either solid-shield or braided-shield variety. Solid-shield cables

are more resistant to external signal coupling and interference, but are generally stiffer than

braided cables. The path or site engineer(s) should be consulted to assure that the proper

materials were chosen for the installation with all factors considered.

Generally, the larger the diameter of the transmission line, the lower the loss. So for longer runs

of transmission line, larger diameter cables are highly advised. However, at every frequency,

there is a maximum diameter cable that will support the operating frequency, so be certain to

verify the specifications. This should have all been determined during the path and site planning

process.

In some cases, the choice of transmission line will not be coaxial cable, but instead will be air-

dielectric waveguide. This is an expensive solution and is generally not necessary, but may be

required for very long transmission line runs and/or for very long link distances and/or for

systems that require extremely high reliability.

The following is a representative sample of transmission line types that are recommended for this

radio:

• Andrew HELIAX

LDF4-50, 1/2-inch solid copper shielded coaxial cable, 6dB/100ft.

• Andrew HELIAX

LDF4.5-50, 5/8-inch solid copper shielded coaxial cable, 4.7dB/100ft.

• Times LMR-600, 1/2-inch braided coaxial cable, 7.3dB/100ft.

• Times LMR-900, 5/8-inch braided coaxial cable, 4.9dB/100ft.

There are several other brands and models of transmission line that are perfectly acceptable. As

mentioned, for extremely long transmission lines and/or extremely long radio paths, it may be

necessary to use waveguide transmission line instead of coaxial transmission line. In these cases,

waveguide type EW52 is recommended, with a loss of 1.3dB/100ft.

It is critical that the transmission line and antenna be capable of supporting the same type of

connector, or easily adapted. Keep in mind that it can be important to minimize the number of

connectors and adaptors, so it is ideal if they match directly without adaptation. In most cases,

transmission line will allow for N-type male connectors and antennas have N-type female

connectors. For waveguide, the waveguide flange can typically accommodate a direct adapter to

an N connector, or alternatively, the antenna can be purchased with a direct waveguide

connection. But often a flexible coaxial jumper is needed to connect between the waveguide to

the antenna, as waveguide is generally inflexible and can be mechanically challenging to align to

the exact antenna connector location.

HELIAX is a registered trademark of Andrew Corporation