7
Receiver
Installation of the receiver unit is basically a repeat of the transmitter installation.
The antenna selection will depend on the distance from the transmitter site and the results
of the site survey.
When the antenna is in position, before finally tightening the fixings and securing the cable,
connect the receiver unit and connect a monitor to the receiver. Check the picture on the
monitor. Again adjust the antenna position if required to obtain the best possible picture.
Because of reflections and multi-path, small movements of the antenna can have a
significant effect.
If a high gain antenna is being used, aim the antenna in the direction of the transmitter.
Make sure that the polarization of the two antennas match. Using the picture on the
monitor, rotate the antenna in the horizontal plane until the best picture is achieved.
Once the best results have been obtained fix all the equipment in position.
Note: As with the transmitter installation, cable lengths should be kept to a minimum to
reduce losses. Again, consider mounting the receiver unit close to the antenna in an
external
General
It is important that antennas are mounted correctly and securely. Remember that on a high
pole, although the antennas are relatively small, there will still be a considerable wind
loading. If in any doubt, contact a qualified aerial rigger.
It is essential that the polarization of the transmit and receive antenna is matched.
Make sure that all connections are weatherproof. This can best be achieved by covering all
connectors with a layer of self-amalgamating tape. Also make sure that cable entries to
buildings are well sealed with mastic.
8
Antenna Mounting
Figure a Figure b Figure c Figure d
The above diagrams show some typical examples of antenna mounting.
a. Not recommended. The mounting pole will have an effect on the antennas
performance and could cause reflections.
b. This is the preferred arrangement where the antenna is clear of the
mounting pole.
c. Not recommended. Although in this position the antenna may work,
especially if the radio path is away from the wall, the proximity of the wall can
cause adverse effects. Many walls, for example, have steel reinforcing or even
metal cladding.
d. This is the preferred arrangement with the antenna clear of the building. A
small pole mounted on ‘A’ brackets may be required to clear the roof overhang,
as shown.
Antenna Types and Performance
Any of the following antennas may be used in combination to give the best possible link
quality. Always make sure that the polarity is matched i.e. both vertically polarized.
High gain antenna, such as the 12dB Patch, should only be used on the receiver. A small
amount of gain is acceptable on the transmitter to compensate for cable losses providing
the ERP (maximum output power at the antenna) does not exceed the limit.
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