Tips and Jottings

Radio Record, Volume II, Issue 7, 31 August 1928, Page 29

Tips and Jottings

Underground Aerials. VERY good results: are obtained by the use of underground aerials for the reduction of statie, but volume is also much reduced. 2wever, there are times when the absence of static is imperative, as it enables the weakened signals to be heard when. they might otherwise be lost altogether. Such an aerial is usually made of a wire enclosed in a len; th of ,ar’en hose carefully stopped up and insulated at the outer end. The aerial is buried a foot or two deep, either in a straight line or coiled up in a hole. Oak Finish for Cabinets. CoN STRUCTORS who build their own. cabinets will find that an excellent stain for oak can be. made by mixing Japan black and turpentine in equal quantities. The. liquid should he applied with a rag to the well-sand- . papered surface, and with two or three coats a rich brown shade will be ob- . Grid-Bias Essential. I pSTENERS should see that when valve replacements become necessary suitable valves are purchased, and here, by the way, it is worth mentioning that frequently it happens in multivalve sets that the changing of the

positions of the valves provides an imrzov ment in reception. In practically every case when a medium-sized or large loudspeaker is employed, what. is known as grid bias is essential to pure reproduction of music. It takes the form of a small dry battery of 44 to 9 volts, and if the listener cannot trace it in his set he should endeavour to get the advice of an experienced friend on the subject. No wireless set employing two or more valves for audio amplify: ing should be. unprovided with a gridbias battery. Watch the A Battery. [THE accumulator employed for lighting the valves must be very carefully used. It should never be allowed to run down to a point where it cannot operate efficiently, Even -when not in use it should be charged at least once a month. . "Adjacent Aerials. AERIALS: in close proximity can cause.a good aniount of interference, and in some cases even a erystal set has. been. known to affect a valve set, either as a circuit absorbing -the oncoming waves; or from’ the scratching of the cat’s-whisker being heard in the valve set. A new listener showld erect his aerial as much at right angles as possible to existing near-by aerials, in. order. to. cut .dowm. possible: ‘interfer ence to a minimum —