This is a kind of low-loss cable, which is formed by injecting gases to make the medium to be foamed. Optimal technological parameters are selected in forming tiny pores, which are closed down from each other. The purpose is to prevent the medium from ageing and damp. The inner conductors of the cable can be pure copper leads, or copper-covered steels, or copper-covered alums. The outer conductors are can be alum/plastic comp[site strip plus is combined firmly with the inner conductors, and there will be no detachment occurring between the medium and the inner conductor even when the temperature is changing or the cable is being pulled or compressed from outside. This type of cables has smaller attenuation than that of other radio frequencies. There cables are used in CATV closed-circuit TV system for HF and super-high frequency transmission, and also used in data transmitting network for data transmission.