Federal Signal Corporation YAGI-1, Руководство по установке

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11
Installing the Antennas
Installation Manual
Federal Signal www.fedsig.com
Installing the Omni and Omni-B Series Antennas
See Figures 2 through 4.
To install the Omni antenna:
1. Install the antenna (using an installation bracket or equivalent) as high as possible,
such that the antenna cable and obstacles allow, and install it on the side of the pole
closest to the receiving station.
Install a service loop when routing the antenna cable.
NOTE: Objects around the antenna affect the antenna. Keep the antenna away from
objects and at least 1/4 wavelength from the siren pole.
(λ = C/f, where C = 1.18 x 10
10
in/sec)
2. Ensure the antenna cable connections are tight. Seal all connection points with heat
shrink or tape and seal with Scotchkote™ or equivalent.
3. Apply RF power to the antenna on the site’s transmit frequency and verify that the
VSWR (Reflected power) is within the antenna’s specification. Record the forward and
reflected power measurements as a baseline. If the reflected power is greater than
(>) 5% over the specification for the antenna, check the antenna and cable for loose
connections or moisture. Repair or replace as necessary. See “Table 3 Determining
Maximum Reflected Power” on page 6 to determine the maximum reflected
power for the antenna being installed.
If the VSWR specification is unattainable, replace the cable. (A simple ohmmeter
check of the cable does not guarantee that the antenna cable is good due to the
DMM not having the ability to check the cable at high frequencies.) If that does not
take care of the problem, replace the antenna.
Figure 2 Omni Antenna Installation Example