Installation Instructions

905U-K.MAN Rev. 1.1 January 2002

 ELPRO Technologies Pty Ltd Page 21

Dipole and Colinear antennas.

A unity gain dipole is the normal antenna for use on unlicensed channels. As it does not

provide any gain, then the power transmitted from the antenna will be the same as the power

out of the module. Dipole antennas are only available with a 15 feet of coaxial cable and SMA

connector for mounting away from the 905U-K module. Dipole antennas should be mounted

vertically, at least 1 metre away from a wall or mast.

For longer, more marginal radio paths higher gain colinear antennas can be used. These must

be used with either CC10/900 or CC20/900 cable.

4mm

DIPOLE AERIAL

MAST

EARTH CONDUCTOR

SHOULD BE 16mm

EARTH STAKE

IF GROUND CONDITIONS ARE POOR,

INSTALL MORE THAN ON STAKE

MAX. COAXIAL CABLE LENGTHS

CC10/900 – 33 feet

CC20/900 – 66 feet

INSTALL AERIAL ABOVE LOCAL

OBSTRUCTIONS

GND

ANT

905U.K

SURGE DIVERTER

COAXIAL CABLE

SEAL CONNECTORS

WITH “3M 23” TAPE

STRESS REDUCTION LOOP

The 905U-K normally produces 1.0 Watt of radio power when an external DC power supply is

used. FCC regulations allow this power may be boosted to a maximum 4.0W by using a

higher gain antennas. These higher gain antennas may also be used to compensate for coaxial

cable loss. The losses are 3dB for every 10m of RG58 cellfoil. If 10m of RG58 cable is used

on a marginal radio path, then a higher gain antenna may be used to cancel the losses in the

cable and boost the transmitted power back to the maximum level.

YAGI antenna.

YAGI antennas must only be used with a cable loss of 5dB or greater so the overall system

gain is less than 6dB. So they should only be used with a CC20/900 cable.

YAGI antennas are directional. That is, they have positive gain to the front of the antenna,

but negative gain in other directions. Hence YAGI antennas are normally installed with the

central beam vertical and must be pointed in the direction of transmission to benefit from the