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9.6 Check that transmit audio distortion is less than 5%. 
9.7 Switch off the audio generator. 

9.8 Set Filter 1 to 50Hz HPF. Set Filter 2 to 300Hz LPF. 

9.9. Check the Hum and Noise 
 
 
 

10. Accessory Test(MODE 1) 

 
10.1 Connect an FM deviation meter (communication test set) to antenna test 
point. 
 

 Set the deviation meter to read peak to peak maximum deviation. 

 

 Set Filter 1 to 50Hz HPF. Set Filter 2 to 15kHz LPF 

10.2 Connect an audio generator (600ohm) to the the remote microphone test 

points.  

10.3 Press PTT on the remote. The deviation reading should be 1.5 Khz 

 

11. Data deviation test (TEST mode) 

Press and Hold “CANCEL”and “3” then reset to go to test mode. Select “2”. 
To exit, press reset button 

 
11.1 Connect an FM deviation meter(HP8920) to antenna test point.  
11.2 Set the deviation meter to read peak to peak maximum deviation.  
11.3 Set Filter 1 to 50Hz HPF. Set Filter 2 to 15kHz LPF. 
11.4 Press RIGHT KEY to send DATA. The modulation meter should read 

±

 

1.5Khz 

 

 

12. Receiver Alignment 

 
12.1 Set Filter 1 to 300Hz HPF. Set Filter 2 to 3kHz LPF. 
12.2 Set the output level of the RF signal generator for -47dBm.  

The generator should be set for 1.5kHz deviation at 1kHz modulation. 

12.3 Check RX audio distortion is less than 5%. 
12.4 Check RX Sensitivity is less than -118dBm by reducing the output level  

of the RF signal generator until a 12dB SINAD reading is achieved 

 
 

13. Squelch Threshold and Hysteresis  

 
13.1 Set Filter 1 to 300Hz HPF. Set Filter 2 to 3kHz LPF. 
13.2 Reduce signal generator level to its minimum level. 
13.3 Increase level in 1dB steps until the unit opens squelch and has steady 
audio output.  

This should occur at or below -120dBm. 

Page 3 of 4

Summary of Contents for CHATNOW 75028 Series

Page 1: ...HP8920A 3 Voltage Regulator Test 3 1Connect a voltmeter to output of regulator TP11 VCC and measure the voltage The DC value must be between 3 45 to 3 58Vdc 4 Low_Battery Detect Alignment 4 0 Connect a voltmeter to TP10 LOW_BATT 4 1 Adjust power supply to 4 80Vdc 10mV 4 2 Select one resistor from R112 to R114 until the voltmeter reading is close to 2 25Vdc 40mV Unit will beep 5 Battery ICON Level ...

Page 2: ...requency is equal to the channel frequency with a maximum error 500Hz VC1 is located near the crystal unit of X1 8 Transmitter Output Power Check No alignment needed 8 1Set unit to channel 1 8 2 Press the PTT switch so unit is in transmit mode 8 3 Transmit power should be below 160mW ERP 8 4 Set unit to channel 14 8 5 Press the PTT switch so unit is in transmit mode 8 6 Transmit power should be be...

Page 3: ...8920 to antenna test point 11 2 Set the deviation meter to read peak to peak maximum deviation 11 3 Set Filter 1 to 50Hz HPF Set Filter 2 to 15kHz LPF 11 4 Press RIGHT KEY to send DATA The modulation meter should read 1 5Khz 12 Receiver Alignment 12 1 Set Filter 1 to 300Hz HPF Set Filter 2 to 3kHz LPF 12 2 Set the output level of the RF signal generator for 47dBm The generator should be set for 1 ...

Page 4: ... 1 5dB The squelch sensitivity should be between 8 to 16dB SINAD 14 Audio output power and distortion 14 1 Increase signal generator level to 47dBm 14 2 Set Ext Load R to 16ohm 14 3 With 1 5kHz deviation at 1kHz modulation set volume for maximum audio Audio power should be between 80mW and 100mW across speaker SP and SP Page 4 of 4 ...

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