User Manual

SECTION 2: FACTORY TEST PROCEDURE

~\Technical Documentation\System Manuals\FCC-Reports\DT450-FCCRpt.doc Page 12

Adjustment / Alignment Procedures

Receiver Injection

Perform the following steps to adjust the receiver injection and injection frequency:

Step 1 Select the TX TEST function on the service monitor. Connect a scope probe from the

monitor’s antenna input connector.

This configuration looks at leakage energy from the VCO so that a frequency

reading can be obtained.

Step 2 Edit the Tune Frequency entry in the service monitor menu so the received frequency is

45 MHz lower than the client’s default receive frequency.

Step 3 Read the VCO frequency error using the scope probe closely coupled to VC01. The

error should be +/-100 Hz or less. If necessary, coarse adjust the VCTCXO ADJ trimmer

for minimum error. Fine adjust RV3 for minimum error. Record this value on the Mobile

Data Radio Performance Test Data Sheet.

Note that some frequency ranges of the DT450 use high side injection. If a reading

not registered, change the Tune Frequency entry for a value 45 MHz higher than the

client’s default receive frequency.

Step 4 Change the Tune Frequency entry on the service monitor to 44.545 MHz. This looks at

leakage energy from the IF local oscillator to enable a signal level reading. Record this

value on the Mobile Data Radio Performance Test Data Sheet.

Step 5 Read the IF local oscillator frequency by touching Y1A with the scope probe. Adjust

trimmer capacitor (CV2A) to the center of its tuning range. Record this value on the

Mobile Data Radio Performance Test Data Sheet.

Step 6 Change the Tune Frequency entry back to the client’s default receive frequency.

Receiver 1

Step 1 Select the RX TEST function on the service monitor.

Step 2 Connect the RF jumper cable to the monitor’s RF input/output connector. This applies an

RF signal to the radio for adjustment purposes.

Step 3 Connect the DMM test leads to ground and to test point RSSI1.

If reading not registered, check the Tune Frequency entry on the monitor. It may

not be set to the client’s default receive frequency.

Step 4 Adjust each pole of filter (FT4A) for maximum RSSI voltage. Go back and forth between

these adjustments until no further increase is noted.

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