© K.A. Enyutin

The ways of improving of protection methods of multimedia cable systems (MCS) against external electromagnetic influences from their electromagnetic compatibility point of view are shown and analyzed. It is shown pvc boxes with metallic coating have a little effect in protecting MCS. These boxes provide comparative protection just in case MCS operate in 600-700 MHz frequency band. Protection effect decreases more than in 5 dB in case of connection one pvc metallic coated box to another. Protection effect decreases dramatically with increasing of MCS operating frequency and number of boxes connections. Shielding effectiveness of an pvc box with an aluminum insertion equals approximately 20 dB and with metallic coating - 18 dB. The interfering influence level on MCS in an pvc box with an aluminum insertion was 300 times less and in a pvc box with metallic coating 10 times less than in unprotected MCS. Cables mutual influence is analyzed in case of being placed in the same box. It is shown that the best protection achieves using a screened cable, a pvc box aluminum insertion shows 5 dB less protection and a pvc box with metallic coating is 20...30 dB or 100-1000 times less effective than a screened cable. Moreover, a pvc box with metallic coating has approximately zero protection effectiveness in case MSC operate in frequencies higher than 800 MHz. A metallic coating of inner surface of pvc boxes has equal effectiveness as aluminum insertions in case MCS operate in 400-600 MHz frequency band