CHOICE OF AN ANTENNA

Daily Telegraph (Napier), Volume 59, Issue 35, 13 March 1930, Page 9

CHOICE OF AN ANTENNA

EFFBOTS ON RECEPTION, The average good receiving antenna is a single wire rnn horizontly between two vertical uprights and at ,right angles to and as far as possible away from, power lines, of other sources of electrical interference. It should be placed as high and as free as possihle from other obstrustions or metal structures of any land. As a rule both the length and the height are coiitrolled by local conditions and the available local facilities, such' as chimneys, " already erected, poles sky- • lights, etc-. The person making the installation should look around and pick the vantag© points that moSt nearly check up with the ideal antenna conditions before putting np the wires. A short antenna gives greater selectivity at reduced signal strength and in general less static. It makes very little difference whether or not ah antenna is indoors or out, provided it is equally free from grounded metal or large pieces of metal likely to affect antenna capacity. A metal roof, metal

lath of reinforcing rods, metal beams, oolums, etc., acts as shields, and as a rule, antenna placed close to them are practically worthless. The antenna should be kept several feet from metal wbere possible. It is a oommon error, declare radio engmeers, to assume that antenna performance depends gn the number of feet ofi multiple-'ivire antennae. Of course, such devices may in some cases produce good results, just as chandeliers, gronnd wires, etc., but such procedure is to he avoided if reliable results arc to be the rule rather than the exception. Freak antennae along with large wire loops and loading coils placed either at the end or intermediate between the end and the receiver should not be used. The latter is particularly objectionable, since it makes accurate compensation of the first tuned stage possible at only one wave length. The greatest difficulty in operation of a portable radio receiver is finding a suitahle aerial and ground. While some commercial portable receivers use a small loop, the majority of radio experimenters are inclined to use a simple set that will require an aerial. The well-known aerial consisting of a short length of flexible insulated wire thrown over the limb of a tree probablv has- been tried hy many. This method is anything but conv-enient. and signals are not any too strong. Likewise the ground for a portable set is also a prqblem, prohahly the most common being a counterpoise formed by running a. length of wire along the surface of the ground beneath the aerial hung from the tree branch. A very satisfactory aerial and counterpoise is a barbed wire fence. By connecting the aerial post of a set with a batterv clip to the top wire of the fence anrl the ground terminal of the set witli ' the bottom wire of the fence good results can be obtained.