RADIO NOTES

Patea Mail, Volume XLVIII, 21 January 1927, Page 3

RADIO NOTES

RADIO BATTERIES. (Concluded.) (By Audition.) The acid of an accumulator should ■be periodically tested with a Hydrometer. Thc-.e tests will show the slate of discharge of-the battery, and when it is necessary to recharge. A fullycharged accumulator will have positive plates chocolate colour, negatives a tight or blue grey, all plates gassing freely, hydrometer reading maximum stationary value, and voltage attained maximum stationary value. A battery requires to be kept clean and dry on die surface, and the terminals occasionally cleaned with weak ammonia, afterwards applying vaseline. B battery accumulators need the same attention as A batteries. Amateurs are often in doubt as to whether radio batteries give off fumes .which will cause corrosion. In discussing this interesting point —the inclusion of batteries within the cabinet —we wish to state it is quite safe to include the A battery, or accumulator B battery within the cabinet. The dry cell B battery, however, is like a wolf in sheep’s clothing, as it undoubtedly produces noxious fumes, and should therefore bo kept outside the cabinet. An accumulator expert declares that anything ho wishes to preserve from rust or damp ho stores in the battery room. In laboratories, electrical apparatus which is to bo kept diy enough for immediate use f is placed in an airtight case with open bowls of sulphuric acid. The only emanations from accumulators arc evapora-. tion of pure water, and (during charging) hydrogen and oxygen, the last being too absorbed with the hydrogen to be able to oxidise anything. The C, or grid-bias battery, should be in good condition, for if its internal resistance becomes excessive distortion of signals and howling may result. This battery not only assists in clarifying reproduction, but also considerably prolongs the life of the B battery. The writer recently saw' a practical example of the importance of grid-bias demonstrated 'by a dealer’s valve-testing” sot. Using a well-known type of valve with 90 volts on the plate, without grid-bias the current taken from the B battery was 9?, milliamps. Then the grid-bias recommended by the valve-makers was applied, and the current dropped to milliamps. It will Burs be seen that the correct adjustment of the 0, or grid-bias battery, will make the B batteries last at least twice as long. GENERAL NOTES. The frequent fading and consequent distortion from station 1\ A, Auckland, is receiving much notice by radio writers through the Dominion. We are of the opinion that nothing short of a substantial increase in power will overcome the trouble. A change of location cannot alter the propagation of the waves through the aether, and radio stations situated in most isolated and unscreened places are subject to pronounced fading.