RADIO NOTES

Waipa Post, Volume 48, Issue 3471, 26 May 1934, Page 3

RADIO NOTES

(By L.W.S.)

Overheating of a storage battery may be caused by too heavy a rate of charging by insufficient electrolyte or by internal shopt circuits in the cells. The plates may become buckled or broken and this may in turn cause the insulators to break permitting adjacent plates to touch each other and so causing a “short.” Besides warping the plates overheating may cause the material on the plates to give way and drop away from (he lead grids. Overheating- also causes the electrolyte to get hot, which results in excessive sulphation of plates and also causes the' electrolyte to evaporate quickly. When transferring a storage batlory hydrometer from one cell to another be sure not to spill any of the electrolyte on the top (of the battery for in such a case there will be a loss of acid and also provide a path for current leakage between terminals. Always keep the top of the battery clean and dry. A good method of cleaning the battery top is to first wipe it over with a rag moistened with ammonia or vinegar and next with a rag saturated with clean water then thoroughly remove the moisure with a dry cloth.

Always treat radio valves with care, never drop them severely or jar when putting them down. Dropping a tube nearly always ruins it, eyen if the glass does not break or the filament still lights. Keep the contact tops clean with fine sandpaper or emery cloth to prevent corrosion, which sets up a high electrical resistance and reduces the efficiency of the receiver.

The function cf a radio frequency choke is to block the flow of high frequency currents in the circuit in which it is placed, and yet to allow the low frequency currents to get by unimpeded. Strange as it may seem the more “careless” you are with the winding, the more effective the coil as a radio frequency 'choke. The worst method is to wind the wire in smooth and even layers, always wind it back and forth at random.

A voltmeter is not a good indicator as to whether a battery is fully charged or not, for being- a high resistance instrument little current flows, and the drop in voltage will not show up. The specific gravity test read on a hydrometer, of a fully charged battery should be about 1250 and the voltage 2.4 V. per cell.

The performance of a frame aerial is largely affected by its size—the larger the frame, the greater the strength of the impulses received by it, but the size of the frame will not seriously affect the selectivity.