23. Measuring the transmitter-notch in the uplink-part of the filter.

23.1 Connect the signal generator to "Ant" directly, or via a 50 ohms cable, 1/2 wave long (68 cm), or 1/1 wave wave long (136 cm).

23.2 Connect a 50 ohms terminator to "Tx".

23.3 Connect the signal detector to "Rx" via a 50 ohms cable, 1/2 wave long (68 cm), or 1/1 wave wave long (136 cm).

23.4 Tune the generator and the detector to the exact repeater-transmitter- (downlink-) frequency.

23.5 Turn up the generator-output, until a good readable value is indicated at the detector.

23.6 NOTICE the signal-level at the detector, and the amount of attennuation at the generator. Do not change the output of the generator at this moment.

23.7 Check that the signal you see is the signal coming through the filter. Disconnect the detector from the filter, and terminate the end of the detector-cable with a 50 ohms terminator. The signal on the detector must disappear.

23.8 If not, you have a problem. The signal then enters the detector directly, and not through the filter. Use your common sense to find how the unwanted signal is entering your detector:
23.8.1 Change positions of the equipment etc.
23.8.2 "Walk" with your hands around the cables and wires.
23.8.3 Shift ferriteclamps on the cables and powerwires.
23.8.4 Fit mains-filters to the powerwires.
23.8.5 Check if the signal is running through the safety"earth" between the equipment.
23.8.6 If the problem persists, your generator and/or detector and/or cables are not sheelded and filtered well enough.

23.9 If OK, reduce the signal of the generator fully and connect the generator-cable directly to the detector-cable.

23.10 Turn up the signal, until the same signal level at the detector is obtained then before when measuring through the filter.

23.11 NOTICE the amount of attennuation on the generator now.

23.12 The difference in attennuation with/without the filter is equal to the notchdeepness in the "Rx"-part of the filter. It must be 90 dB or more.


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