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Note the polarity markings on the antennas and orient them so that transmitter and receiver
antennas are polarized the same way. Start with the vertical polarity marks pointed up (see the
sections on Omni and Panel Antennas for example diagrams).
Increasing Range
One of the most popular uses for directional antennas is to increase range. Adding a directional
antenna to the transmitter can increase effective range significantly, even if the power of the
directional antenna is no greater than the omni-directional unit it replaces. Some of the longest
distance transmissions have been achieved with yagi antennas connected to both receiver and
transmitter, and with the antennas correctly like-polarized and pointed at each other. Note that
the tight beam angle of these antennas requires careful aiming to get the antennas aligned.
Reducing Interference
Using directional antennas can effectively reduce the amount of reflection or
multi-path
signals
created by your broadcast, and can also help your system “cut through” interference created by
other systems operating in the area. Using a directional antenna with lower broadcast power
can be a very effective combination.
Using directional antennas at lower power settings can also reduce the amount of interference
that
your system creates for other systems
operating in the same part of the spectrum, while still
giving you the punch and fidelity you need.
Splitters
Sometimes you may want to broadcast to two different areas, which are divided by a barrier or
are separated in some way. You can achieve this by using a pair of identical directional
antennas and a splitter. When using this solution, there are a few things to remember:
•
The antennas must be identical
•
The splitter will divide the transmitter power between the antennas, so each will be only
half the output that the same antenna would have alone
•
Position the antennas so that the beams don’t overlap; overlapping can cause signal
corruption and poor reception
•
Height improves fidelity
Cables
Radio performance can be impaired if poorly made or excessively long cables are used for
antenna connection. It is important that the correct coaxial cable material is used and that the
cable is properly assembled. See the Cable Chart below for details regarding cable loss verses
cable length. CTI’s antenna adapters and extension cables are carefully matched to our radio
transceivers and antennas to assure the best possible operation. Cable performance can be
significantly impaired if the cable is sharply bent or kinked, or if it is compressed in some way.
When installing antenna cables, be careful not to bend cables excessively or kink them. If strain
reliefs such as cable ties are used, be careful not to over-tighten them.
Extension cables may also be used to locate the antenna some distance from the Transmitter or
Receiver. All cables, whether short adapters or longer extension cables, must be properly
constructed from materials intended for RF applications. Cables that are made from improper
components or are poorly assembled can impair or completely block radio transmissions.
