Decoding Repeater Signaling Data; If No Decoded Data Is Displayed - HP 8920A User Manual

Chapter 8, Signaling Decoder Screen
Using the LTR Decoder

Decoding Repeater Signaling Data

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Press the PRESET key.
1. Access the DUPLEX TEST screen.
2. Set the Tune Mode to Manual.
3. Enter your repeater's transmit frequency in the Tune Freq field.
4. Select the Input Port (RF IN/OUT for direct transmitter-to-Test Set connections;
Ant (ANT IN) for off-the-air measurements).
5. Attach an antenna to the Test Set if you are making off-the-air measurements.
6. Access the DECODER and select the LTR mode.
7. Set the LTR display field to Repeater.
8. Select the triggering mode.
• Select Single to decode and display only the first valid transmitter data received.
The decoder must be re-armed before another measurement can be made.
• Select Cont to continuously monitor a repeater and display its transmitted data.
9. Set the AF Anl In field to FM Demod.
10. Set the Input Level to 1 kHz.
11. Select Arm Meas if you are using single triggering. The transmitted data is displayed
after computing is displayed in the Status field.

If no decoded data is displayed

• The repeater may not be transmitting.
• The RF signal may be too low for off-the-air measurements. Use a better antenna,
or set the RF ANALYZER screen's Sensitivity field to High.
• The Gate Time may be too short. Increase the value.
• The received data may be inverted. Set the Polarity field to Invert.
• The trigger level may be too low or too high. Change the Input Level setting.