An improved aerial

744,239. High-frequency impedance networks. DEPARTMENT OF AIR, SECRETARY OF. July 11, 1952 [July 13, 1951], No. 17602/52. Class 40 (8). [Also in Group XL (c)] An impedance network for preventing coupling between two aerials 20, 21 comprises concentric stubs 24, 25 tuned to a frequency either above or below the operating band of the aerial system, i.e. they are anti-resonant at a frequency outside the operating band, and concentric tube stubs 26, 27 which are also anti-resonant to a frequency outside the operating band. Stubs 24, 25 provide a high series impedance between the aerials along the mast 4 whilst the stubs 26, 27 break up the outer tube 28 into two parts separated by the two high impedance stubs 26, 27 and thereby prevent the formation, on the outside of the suppressor stubs, of a low impedance capable of readily coupling to both aerial units and upsetting their behaviour in the pass band.