Codan MT-4E, Руководство по обслуживанию

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MT-4E ANALOG & P25 DIGITAL RADIO SYSTEMS | MAINTENANCE GUIDE
Chapter 5: Codan Radio System Testing Page 25
Reference Sensitivity:
Monitor the SINAD meter while slowly reducing the RF carrier level as shown in Figure 5-6. The 12
dB SINAD point should be at an RF carrier level less than the specifi ed Analog Sensitivity point of the
receiver. The high and low alarms are set for 11.5 and 12.5 dB SINAD to help you locate the 12 dB
SINAD point. When the indicator bar turns green, the signal is close to 12 dB SINAD.
Figure 5-6: Receiver Reference Sensitivity Measurement
Enter the Reference Sensitivity (12 dB SINAD) reading on the MT-4E Test Sheet.
If the distortion or reference sensitivity measurements are not within Codan published specifi cations,
the RF Preselector may need re-alignment. Refer to the Receiver RF Preselector Alignment and Tuning
section.
Squelch:
Adjust the RF carrier level up and down until the receiver squelches and unsquelches. There should
be approximately 6.0 dBm of hysteresis between the squelch and unsquelch points. The squelch point
can be adjusted in the Squelch Levels area of the Service section on the RSS.
The Receiver operates on a Noise based squelch (default) or a Received Signal Strength based
squelch (optional). The squelch can be set globally for all channels, or on a per channel basis. To set
the squelch Open and Close points, inject an RF signal at the desired Open or Close level and click
the Set button.
Enter the Squelch and Unsquelch readings on the MT-4E Test Sheet.