After the cable inlet, we tested the change of the characteristic impedance, when the cable was damp and the TV signal passed through the cable, the measured level value was lower than the cable's specified loss value. According to the length of the cable inlet and the damp time, the corrosion of the conductor and the degree of oxidation rust are different.Coaxial Cable Different degrees of the cable damp, water after the resistance, capacitance, inductance, level changes. The data shows that the difference of the degree of water inlet of the cable can also lead to the distribution capacitance, inductance corresponding change, its characteristic impedance will also change, because the coaxial cable inside and outside two conductors there is an electric field, there is a certain amount of electrical capacity, the conductor through the alternating television signal will produce a certain inductance, these inductors, capacitors in the cable distribution, The inductance and capacitance C of the coaxial cable are measured in the series inductance and the parallel capacitor combination, and the characteristic impedance Z of the coaxial cable is formed.Coaxial Cable

From the characteristic impedance formula, the change of inductance L and capacitance C can lead to the change of characteristic impedance. The data of cable capacitance and inductance were analyzed after water accumulation. The more the inflow, the larger the capacitance and inductance, the more the characteristic impedance must change, which causes the input impedance of the signal source to be different from the characteristic impedance of the cable, which is called mismatch. Finally, the power loss is increased and the power loss of some effective signal is lost.Coaxial Cable Theoretically, the attenuation of coaxial cable is mainly caused by the loss of "skin effect" of inner conductor. The more Gaoji the skin effect, the more the series inductance inductance (WL), while the Capacitance resistance (WC) of the shunt capacitor decreases, the bypass leakage of the external conductor on the inner conductor increases, so the higher the frequency, the longer the cable transmission distance, the greater the attenuation.Coaxial Cable