RADIO TOPICS.

New Zealand Herald, Volume LXVI, Issue 20218, 1 April 1929, Page 12

RADIO TOPICS.

ECONOMY IN UPKEEP* DRAIN ON BATTERIES. It is well for prospective purchasers of radio sets to remember that tho initial cost is not the only outlay. In valvo sets tho upkeep of batteries has to be reckoned with, and the necessity for using tho right type of cell cannot be too strongly stressed. Appearance, range, selectivity, volume and tone quality are tho five cardinal features usually investigated by buyers of radio receivers. Those are the general qualities most frequently emphasised in advertising and most foicefully stressed in selling. They are important, so far as the ultimate enjoyment which may be derived from tho purchase is concerned, but the cautious buyer gives the matter of upkeep cost as much consideration as any one of theso factors. " Milli-amperes of 'B' battery current " is the measuw by which tho upkeep cost of a receiver should be judged. Valves and battories are practically the only expenses involved in keeping a good radio receiver in operation. The "B" battery current is most significant because indirectly it involves valvo renewal as well as "B" battery costs. But how many receivers are bought with a definite knowledge of how much they cost to run? So little attention has been given to tho basis of judging tho relative value of receiving sets that most owners aro astounded to learn of the wide variations in upkeep cost encountered with different makes and types of receivers. Some, equipped with high-grade batteries of adequate capacity, cost but Id or an hour to run; others, giving no greater volume or range, and powered with inadequate and unsuitable "B" batteries, may cost as high as lOd an hour to keep them going. Tho Question of Cost. In deciding between two receiving sets and their associated battery equipment, a matter of £1 or £2 difference in first cost is of insignificant importance, as cornpared with a saving of 9d an hour in maintenance cost. As a matter of fact, there are receivers in the same price class and of equally attractive appearance, which differ 2 to 1 in "B" battery current drain and may differ in a ratio of 10 to 1 in"B" battery maintenance cost, because often through a limited battery compartment space they require the use of batteries of insufficient capacity. Therefore, when deciding upon tho respective merits of a number of receiving sets it is desirable to know both tho actual current drain in milli-amperes and what size of "B" battery will furnish that amount of current most economically. Thero is no reason why even a multi-valve set should cost more than Id or an hour for the "B" batteries, and at that prico radio is the most inexpensive form of entertainment and education. The Number of Valves. The number of valves which a set has is sometimes used as a criterion in judging tho upkeep cost of a receiver. Really, this is no guide whatever, for some threevalve sets are so designed that they draw more current than other well-designed sixvalve sets, just as thero aro somo heavy and wasteful four-cylinder motor-cars which travel only nine miles per gallon of petrol, and, on the other hand, some welldesigned six-cylinder cars which make 23 miles to a gallon. For instance, one highgrade three-valve set tested recently used but 7 milli-amperers of plate current; another, having the same number of valves, used 18; yet tho wasteful receiver was in no way superior to the economical one. Ono six-valve super-heterodyne receiver draws but 13 milli-amperes, while a well-known make of five valve tuned radio frequency receiver put a load of 26 milli-amperes on its overworked "B" batteries. A still greater surprise was occasioned by a home-made super-heterodyne of very wasteful design which reflected the needle of the milli-ammeter in its plato battery lead until it recorded 90 milliamperes ! Probably its owner never considered his upkeep cost until he found it necessary to renew his "B" batteries every few weeks. A few design changes so reduced the plate current that "B" batteries are now good for four months with this setEconomical Operation. The laboratories of "B" battery manufacturers have been working night and day for many years to produce more economical and more eificient radio batteries. That their products are able to supply unvarying power for such a wide range ot current drains as are encountered in radio reception is evidence of the success which has attended their efforts. But no matter how efficient the battery it will not do the impossible, economically. If it is necessary to renew your "B" batteries more frequently than once each four or six months, inquire carefully into the design of your set, the make of the battery which you use. and its size. Remember that the smaller the battery the smaller its capacity, and, consequently, the higher its operating cost per hour. Use the largest size of "B" battery which you can afford, for it is the least expensive wav to power vour receiver. ' When you purchase a receiver do not overlook tho factor of economical operation. Make sure that tho set is designed so as to use the small "B" battery current; buy a battery of adequate size for the service which it is called upon to deliver, and. thirdly, buy a battery of known and reputable make.