The power rating (thermal) of radio-frequency cables

The principles used in calculating the temperature rise in cables which are required to transmit radio-frequency power are considered. The theoretical attenuation characteristics and power ratings of a number of standard r.f. cables are set down in graphical form for a wide range of operating frequencies. The ratings are based on a maximum temperature rise of 30 deg C, in an ambient of 55°C, established in a matched line for the steady-state condition. The use of suitable ¿rating factors¿ for other operating conditions is proposed. The effect of such operating conditions as the presence of standing waves and the effect of end cooling are briefly considered in relation to the rating of the cables.