AERIALISMS

Sun (Auckland), Volume III, Issue 640, 17 April 1929, Page 15

AERIALISMS

If an aerial is surrounded by tall buildings, trees, etc., these absorb some of the energy which should reach it from distant broadcasting stations, and the aerial is therefore said to be screened. V * • A good high aerial is always an advantage, but it is particularly so in the case of crystal receivers, as this rlass of set is' worked entirely from the power which is picked up by the aerial. Good conductivity copper wire niak°s the ideal aerial, the sort known a s 7/22 having proved particularly efficient in operation. Instead of using stranded wire, of the 7/22 type, for aerials, it is possible to use one single wire of heavier Stage with good results (it should preferably be enamelled wire, and a suitable gauge is 18 or 20). * • * To avoid the annoyance of the need for continual adjustment, it is a good Plan to wire a spare crystal detector '■lose beside the existing detector of T he set. A switch can then very easily be arranged to bring either one

or the oilier detector into circuit, so that if one is temporarily out of adjustment the programme is not interrupted while this is right. It is essential to allow good spacing for wiring of the high frequency circuit of any valve receiver. Crystal detectors of the semipermanent type, in which two crystals are used in contact w'ith each other, are often rendered more sensitive by varying the pressure holding the two crystals together. When celluloid accumulators are used, it is a good plan to get the acid renewed about once a year. The renewal of the acid in an accumulator is not a job for inexperienced persons, so that this is always better carried out at a reliable service station. If the level of the liquid in an accumulator is allowed to fall below the tops of the plates, the deficiency should immediately be made good with distilled water. Never drop the telephones upon the floor, as the permanent magnetism is likely to be destroyed or -weakened by shocks of this kind.