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WARNING: Disconnect primary power prior to servicing.
Overall System Theory
4.3.5 Harmonic Filter
The vertical transmission line at the rear of the cabinet contains the Harmonic Filter
which is connected directly to the output of the Z-Plane via a transmission line
connection which is routed under the PA deck and through the power supply
compartment.
4.3.6 Directional Coupler Assembly
The directional coupler assembly is installed directly before the output from the
transmitter. It consists of 3 identical directional couplers with two of the couplers
adjusted to produce a sample of the forward output power, and one coupler arranged
to provide a sample of the reflected output power. The isolation, or directivity, of the
couplers is better than 30dB, with 40dB typical.
NOTE:
The reflected coupler cannot be interchanged with the other 2 couplers due to
the different coupling ratio for the forward and reflected samples.
The typical coupling ratio for each of the couplers is given below:
• Forward Coupler - 48.8dB @ 88MHz to 47dB @ 108MHz
• Reflected Coupler - 43.8dB @ 88MHz to 42dB @ 108MHz
Typical tolerance is +/- 0.1dB but this is not guaranteed since any minor variation
can be factored out by using the calibration procedures.
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