GB791585A - Aerial elements - Google Patents

Abstract

791,585. Aerials. SIHN, W. Aug. 24, 1956 [Aug. 25, 1955 ; Aug. 25, 1955; April 26, 1956], No. 25892/56. Class 40 (7). An aerial element of adjustable electrical length comprises a hollow outer member 2 and an adjustable inner member 3 slidable in a bore formed in an intermediate sleeve 4 of resilient material providing a watertight seal, the inner member being formed with annular grooves 6a, 6b, 6c, &c. and the sleeve having an inwardly directed bead 7 about one end of the bore (as shown more clearly in Fig. 2) which snaps into the grooves to hold the aerial adjusted at predetermined electrical lengths. The inner and outer members are isolated electrically by the intermediate sleeve, although where it is found to be desirable to provide electrical contact, an insulating member 5 which supports the inner end of member 3 may be replaced by a contact system, Fig. 7 (not shown). To facilitate the adjustment of an aerial array, particularly one comprising a large number of elements constructed according to the invention, the various sections of members 3 are coloured differently as indicated at 18a, 18b, 18c, &c. The sections are cut away intermediate the annular grooves to prevent the coloration from wearing off, Alternatively the sections may be numbered or incorporate a scale. Fine adjustment of the aerial element may be provided by means of a magnetic or dielectric device in association with member 3. In one construction, Fig. 3 (not shown), the member 3 carries a short sleeve which slides over the outer portion and is held in position by friction or a bead arranged to engage the annular grooves. In another construction, Fig. 4, (not shown), the magnetic or dielectric device takes the form of bell-shaped member adjustably mounted of member 3 with the mouth pointing back towards the inner member, the mouth being of sufficient diameter to pass freely over the outer member as the device is adjusted inwardly. Member 3 is coated with a material of a high dielectric constant. In yet another construction, Fig. 5 (not shown), a metal rod is provided as an adjustable core in member 3, and projects into member 2 to vary the coupling between members 2 and 3. Fig. 6 (not shown), illustrates a construction in which member 3 is constructed as a metal core with a magnetic or dielectric sheath. In connection with this embodiment, reference is made to the use of assembly comprising an inner member and intermediate sleeve for attachment to an existing aerial element to make it adjustable. Aerial elements constructed according to the invention are stated to be of use with dipole aerials, reflectors, directors, direction-finding aerials and television aerials.