GB583731A - Improvements in turnstile antenna - Google Patents

Abstract

583,731. Aerials; impedance networks. FARNSWORTH TELEVISION & RADIO CORPORATION.' Nov. 23, 1944, No. 23381. Convention date, Feb. 14. [Classes 40 (iii) and 40 (v)] A turnstile antenna, consisting of four equal length radiator elements located in the same plane at 90 degrees spacing, has a pair of quarter - wavelength transmission lines connected respectively between separate pairs of adjacent elements and means for matching each radiator element impedance to the characteristic impedance of the transmission lines, two opposite radiator elements being coupled in phase opposition to the conductor associated with the radio apparatus. In Fig. 1, the 4 radiators N, E, S, W, each a quarter-wavelength long, have quarter-wavelength transmission lines 15 and 16 connected between the inner ends of N and W, S and E. Condensers 11, 12, 13, 14, one side of each of which are grounded, are used to tune their respective radiators to resonance and adjustment of the effective length of the radiators, with corresponding adjustment of the condensers to maintain resonance, is then made to match the impedance to the radiators to that of the attached transmission lines. The outer sheaths of the transmission lines are earthed as shown. A full wavelength line AB, Fig. 2, is connected to the points A and B, Fig. 1, and a feed connection C attached to it at D such that AD is a quarterwavelength and BD three-quarters of a wavelength, whereby the radiators are excited in phase quadrature. It is stated that providing the radiators are all equally long, the length may be any desired value and in some cases inductive elements may then be required instead of condensers for tuning. An alternative form of phasing and feeding system utilising a balanced network of 2 condensers in series with an inductor may be used, Fig. 3 (not shown).