Tuning Capacities for Frame Aerials

Radio Record, Volume II, Issue 4, 10 August 1928, Page 30

Tuning Capacities for Frame Aerials

HE following figures may he of use . to experimenters who are desirous — of constructing loop aerials. for their receivers. In order to cover the broadeast band. of, say, 200 to 500 metres, the spacing between turns, being ahout zin., the following dimensions and ' tuning condenser capacities will be found useful. For a loop of about uft. square, and taking tuning capacities of 0.00025, 0.00035, and 0.0005, the number of turns will be respectively 20 turus, 14 turns, and 10 turns For a loop of about 8ft. square and using tuning condensers of the same three capacities, the turns will be respectively 16, 12, and 8. For a loop of about 4ft. square the turns for the condensers mentioned will be respectively 12, 8, and 6 These figures are given on the assumption that the loop is of the flat or the box type. In the latter the windings are all of the same area, whilst in the former. type the area of the windings becomes smaller towasds the centre.: In using the foregoing figures with the flat type, take the area as keing the’ average area of the loop. %t may be mentionec that the box type for a given area will be more sensitive as a pick-up of signal energy, put the flat or pancake tyne will be su-

perior in directional properties. Again the flat loop is to be preferred with unshielded frame aerial receivers be‘ause of minimised coupling between the loop and the coils in the receiver. -~