Hytera MD78X, Service Manual

Page: 449 / 519

VHF (136MHz
–
174MHz)
Troubleshooting Flow Chart
33
Description of normal situations:
[1] During sensitivity test, use a communication test set to demodulate the audio signal at TP4012 and
TP4016. If the signal is demodulated normally, it is concluded that the front panel is defective.
[2] Use the communication test set to apply a 44.85MHz IF signal at the mixer, and sensitivity is about
-117 dBm.
[3] There is a second LO signal (47.1 MHz) at TP704.
[4] Use the communication test set to apply an RF signal of -100 dBm, and the sensitivity at TP6101 is
about -110 dBm
[5] The received LO signal at TP6106 is about 18 dBm.
[6] Use the communication test set to apply an RF signal of -110dBm, and the sensitivity at TP6104 is
about -120 dBm.
[7] Use the communication test set to apply an RF signal of -110dBm, and the sensitivity at TP6103 is
about -117 dBm.
6.5
Frequency Generation Unit (FGU)