GB464825A - Improvements in or relating to high frequency electric feeder systems - Google Patents

Abstract

464,825. Loading. CORK, E. C., and PAWSEY, J. L. Oct. 22, 1935, Nos. 29152 /35 and 14719 /36. [Class 40 (iv)] [Also in Groups XL and XXXVI] Variation of the input impedance, within the operating frequency band, of a feeder caused by localized impedance, or the input impedance of an aerial due to weather changes of the insulators, is neutralized by suitable placing of other localized impedances. The Figure shows a concentric feeder terminated by an aerial represented as ZO its characteristic impedance. The effect of the insulator 12 in causing the input impedance to vary widely with a small change in frequency is overcome by placing a similar insulator 13 a quarter of a wavelength away. Alternatively the capacity of the line may be reduced by increasing the ratio of the radii of the outer and inner conductors, which also causes an increase in the inductance of the line at the point, or an integral number of half wavelengths away. The principle may be applied to cases such as bends in feeders where extra supporting insulators are used, and to expansion joints which are made one quarter or half wavelength long according to whether the characteristic impedance of the section is the same as the feeder, or not. In the case of an aerial or an open line feeding an aerial, changes due to weather affecting insulators are neutralized by providing similar insulators one quarter of a wavelength apart which are affected in the same manner. Specification 429,146, [Group XL], is referred to.