衰减常 数 dB/100m 20°C≯ 回波损耗 ≥dB | 50MHz 200MHz 300 450 550 750 800 1000 VHF UHF | 75±3 4.4 9.0 11.2 14.0 15.6 18.3 19.1 21.5 20 18 | 75±2.5 3.8 7.7 9.6 12.0 13.4 15.8 16.3 18.2 20 18 | 75±2.5 3.0 5.9 7.4 9.3 10.4 12.4 12.8 14.4 20 18 | 75±2.5 0.3 4.6 5.7 7.1 8.1 9.5 9.9 11.2 20 18 | 75±2.5 1.6 3.4 4.5 5.5 6.0 7.6 7.8 9.0 20 18 |