Page
13
February 2010
The gains and losses of typical antennas are
Antenna
Gain (dBi)
Dipole
2
Collinear
5 or 8
Directional
10 - 28
Cable type
Loss (dB per 10 m / 30 ft)
RG58 Cellfoil
-6
RG213
-5
LDF4-50
-1.5
The net gain of the antenna/cable configuration is determined by adding the antenna gain and the
cable loss. For example, a 5dBi antenna with 10 meters of Cellfoil has a net gain of -1 dB (5dB
– 6dB).
Installation tips
Connections between the antenna and coaxial cable should be carefully taped to prevent ingress
of moisture. Moisture ingress in the coaxial cable is a common cause for problems with radio
systems, as it greatly increases the radio losses. We recommend that the connection be taped,
firstly with a layer of PVC Tape, then with a vulcanizing tape such as “3M 23 tape”, and finally
with another layer of PVC UV Stabilized insulating tape. The first layer of tape allows the joint
to be easily inspected when trouble shooting as the vulcanizing seal can be easily removed.
Where antennas are mounted on elevated masts, the masts should be effectively earthed to avoid
lightning surges. For high lightning risk areas, surge suppression devices between the module
and the antenna are recommended. If the antenna is not already shielded from lightning strike by
an adjacent earthed structure, a lightning rod may be installed above the antenna to provide
shielding.
2.2.1
Dipole and Collinear antennas
A dipole or collinear antenna transmits the same amount of radio power in all directions - as
such that are easy to install and use. The dipole antenna with integral 5 meters (15 feet) cable
does not require any additional coaxial cable; however a cable must be used with the collinear
antennas.
Collinear and dipole antennas should be mounted vertically, preferably 30 cm (1 foot) away from
a wall or mast to obtain maximum range.
