In the cable television system, some common faults caused by cable joints mainly include the following seven points:If the ghost cable joint fails (such as looseness, deformation, poor contact, water ingress, etc.), the characteristic impedance of the connection is Changes will occur, resulting in impedance mismatch and ghosting. Ghosting easily appears on channels ch1 to ch3.
Increased attenuation of low-channel signal level. If the coaxial cable attenuates low-channel signals small and low-channel signals, this is caused by the increase in the contact resistance between the outer conductor of the cable and the cable connector.
The reason is that in addition to impedance mismatch that causes a certain reflection loss in the low frequency band, the signal path in the outer conductor mainly depends on the distributed capacitance. This capacitance is generally small, so the attenuation of the high frequency signal is small, and the attenuation of the low frequency signal Obviously increase, the attenuation value is generally between 10 ~ 20dB.
The voltage fluctuation of the cable power supply drops. When the main line amplifier adopts cable power supply, the contact resistance of the cable connector increases due to loosening, water ingress, and corrosion, which causes the power supply loop resistance to increase, and the voltage drop at the connector increases.
Reduce the working voltage of the main line amplifier after supplying this connector. As a result of the reduced power supply, the loop current will increase. When the contact resistance changes suddenly, the supply voltage of the mains amplifier will also fluctuate.