LOOK TO YOUR AERIAL

Radio Record, Volume I, Issue 12, 7 October 1927, Page 14

LOOK TO YOUR AERIAL

IS TIIS LEAD-IN JOINED ON CORRECTLY ? Glancing skywards, one cannot help noticing the different ways in which aerials are erected, and the lead-in wires arranged. Some otherwise very good inverted I, aeriais are spoilt by the lead-in being attached to the aerial wire at a distance of anything up to five or ten feet from the actual end where it should be placed, Then there is the aerial that pretends to be « T, but isn’t. An efficient Lf aerial should have arms of equal length, that is, the lead-in must be joined on at the exact halfway point. Yet it is a common thing to see such an aerial erected and the lead-in joined on many feet from the centre, and one naturally wonders just how muclt trouble this misplacing of the lead-in.is causing. Hlow does the oscillatory flow of current take place in the case of the T type aerial when induced by the incoming ether waves? It will commence its flow from the two extreme ends of the two "farms" simultaneous. lv, wil: combine at the point where the down lead is connected, will rush to earth through the set, back through the set up the down lead (or should we say in this case up the up-lead ?), divide at the point of connection, flow to the extreme ends of the two arms, and will return and repeat the cycle until ‘‘worn out," or will continue its "swing" if the circuit is tuned so that it arrives back at its starting point just in time to be pushed off by the next incoming wave-in other words, if the circuit is tuned in. Now what happens when the two "arms"? are not of equal length is simply this, and that is that in the first place the current starting from the extreme end of the shorter arm will get to the down lead first and will precede the current from the other arm, will complete its journey to earth first, naturally, and will have turned to come back only to find that the other is opposing it as it has not yet finished its journey to earth. So instead of combining together at the down lead each time and again at their point of return, thus forming, as i€ ‘vere, one combitied current, it will tend to be divided into two separate cutrents which will oppose each other at various points, with the result that reception willbe, to say the least, inefficient. This condition must | obtain, therefore unless the down-lead is in the absolute centre or at one extreme end of the aerial, ‘