TECHNICAL MANUAL FOR COMPACT VHF DSC RM2042

3 SERVICE RM2042CHECK OF RECEIVER SENSITIVITYThe receiver sensitivity is controlled by applying a RF-signal to the antenna terminal and then measuringthe output signal-to-noise ratio (SND/N) by means of a voltmeter.1. Connect a RF-signal generator to the antenna input and adjust the carrier level to -119 dBm (EMF:-6 dB/µV). Modulate the carrier with 1 kHz to a peak frequency diviation of 3 kHz.2. Connect a voltmeter to the analog switch output, pin 14 at U6-3, for measuring the AC-voltage.3. Read the meter deflection by means of the dB scale.4. Remove the modulation and control that the output level decrease more than 12 dB.CHECK OF RECEIVER DISTORTIONThe receiver distortion is controlled by applying a RF-signal to the antenna terminal and then measuringthe output distortion by means of a distortion meter.1. Connect a RF-signal generator to the antenna input and adjust the carrier level to -30 dBm (EMF:83 dB/µV). Modulate the carrier with 1 kHz to a peak frequency diviation of 3 kHz.2. Connect a distortion meter to the analog switch output, pin 14 at U6-3, for measuring the receiverdistortion.3. The measured distortion shall be less than 3%.CHECK OF DSC CALL SENSITIVITYThe DSC call sensitivity is controlled by modulating a RF-signal generator with a DSC call, which isgenerated by the DSC unit it self.NOTE! To perform this test, it is necessary to change the operation mode of the RM2042 from user toservice mode. This change of operation mode is only allowed for trained technicians and the informationof how to do it, is therefore only included in the DSC-VHF INSTALLATION GUIDE.1. Select the balanced TX AF amplifier as interface to the RF-signal generator, by turning the switchS1-1 at the interface module into the position: ‘E’.2. Connect the output of the balanced TX AF amplifier to the external modulation input of the RFsignalgenerator. Use pin 4 (TX AF+) and pin 8 (TX AF-) in the 9 pole SUB-D connector P2(connector for VHF tranceiver).3. Connect the output of the RF-signal generator to the antenna terminal of the RM2042.4. Apply an external modulated carrier with the frequncy 156.525 MHz to the antenna terminal andadjust the output level to -113 dBm (EMF: 0 dB/µV).5. Change the operation mode of the RM2042 from user to service mode.6. Select the ‘FUNC’ menu and then the ‘Test’ menu. Select ‘Dot pattern’ by means of the ‘left-arrow’or ‘right-arrow’, and press the ‘NEXT’ button.7. Adjust the peak diviation at the RF-signal generator to 3400 Hz and press the ‘STOP/ENT’ buttonto terminate the transmission of dot pattern.8. Select ‘Test call’ by means of the ‘left-arrow’ or ‘right-arrow’ and press ‘NEXT’ to start the continoustransmission of a test call to the unit it self.9. Now control that the RM2042 is receiving a continous sequence of individual calls.10. Terminate this procedure by turning the RM2042 off. Remember to change the operation modeback to user mode.PAGE 3-49403