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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.
4.3.6 Directional Coupler Assembly
The directional coupler assembly is installed directly before the output from the
transmitter. It consists of 3 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:
Note that the reflected coupler cannot be interchanged with the other 2 cou-
plers 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 using the calibration procedures).
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