Motorola F2265A, Owner'S Manual

Page: 16 / 24

Installation
2-4
2.4 BASE STATION INSTALLATION
INSTRUCTIONS
2.4.1 ANTENNA INSTALLATION
The recommended length of antennas for base stations
is 23 to 60 feet for long wire antennas and 23 to 35 ft
for whips, in the specified frequency range. Shorter
antennas are recommended for mobile installations
only.
2.4.1.1 23 to 35 Feet Whip Antennas
23 to 35 feet whip antennas are suitable for medium to
long-range communications. The antenna should be
located away from interfering structures, such as metal
masts, building and metal wires parallel to the antenna.
The distance from these interfering structures should be
about one wavelength (see footnote below) of the
lowest frequency used.
2.4.1.2 23 to 60 Feet Wire Antennas
The wire antenna can be installed in one of the
following configurations: inverted "L," and sloping
wire, as illustrated in Figure 2-5 and Figure
2-6.
The antennas illustrated in these figures are suitable for
systems using frequencies below 5 MHz. Optimum
antenna performance is achieved when the antenna is
approximately a quarter of a wavelength long (see
footnote below).
Figure 2-5. Inverted "L" Antenna
Figure 2-6. Sloping Wire Antenna
If the lowest used frequency is higher than 5 MHz, a
good practice is to shorten the overall antenna length to
approximately a quarter of a wavelength with the
configuration and the wire length ratio as in Figure 2-5
and Figure
2-6.
For antenna length computational purposes only, the following formulas may be used for calculating the
wavelength:
Wavelength (m) =
) ( MHz f
285
Wavelength (ft) =
) ( MHz f
935
If the system uses frequencies ranging between f1 and f2, a satisfactory antenna length is a quarter of a wavelength
of the mean frequency, where:
f
mean
=
2 1
f f
×