Federal Signal Corporation YAGI-1, Installation Manual

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9
Installing the Antennas
Installation Manual
Federal Signal www.fedsig.com
BURN HAZARD: Antennas may cause severe burns. Do not touch the antenna
while the radio is transmitting.
Final VSWR Tuning
To final tune the antenna:
1. Before the final installation of the antenna, temporarily set it up in a clear area at least
6 feet above the ground.
NOTE A: Do not touch the antenna while the radio is transmitting.
NOTE B: Ensure the antenna does not touch any conductive material and is pointed
away from all objects and people. Pointing the antenna at objects nearby may act as
a reflector and create inaccurate readings.
2. Apply RF power to the antenna at the transmit frequency to be used at that antenna,
and check for the low VSWR while performing each of the following steps.
A. Loosen the setscrew with the hex key provided and slightly adjust the aluminum
gamma tube for the lowest VSWR (Reflected power).
B. Adjust the gamma link along the driven element for the lowest VSWR.
C. Repeat the above steps until the lowest VSWR is achieved. Reflected power must
be less than 10% of the forward power.
D. Return to the dimensions shown in the antenna instructions if there is trouble
achieving a good match. If the element dimensions are incorrect for the
frequency being used, low VSWR may be unattainable. If the VSWR specification
is still 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.