Useful Suggestions

Radio Record, Volume II, Issue 27, 18 January 1929, Page 28

Useful Suggestions

An Improvised Aerial. THMPORARY aerial and earth ean be obtained if a receiver is required to be operated out of doors, if a nail is driven into the trunk of a tall tree, ten or twelve feet from the ground, and a similar one as close to the earth as possible. With a piece of flexible wire, join the higher nail to the aerial terminal of the set, the lower one, connect to the earth, or ground terminal of the receiver. Balanced Valves in Push-pull. READERS who use push-pull circuits should make a point of checking the emission of their valves from time to time, to see that one or the other has not seriously fallen off, thus upsetting the balance. A paper label should be stuck on each of the push-pull valves, and the emission at zero grid volts for a given plate voltage marked when the valve is new. No elaborate apparatus is necessary to make this check. It is advisable not to keep the vale alight for more than a minute or so at zero grid volts. Some of the modern super-valve valves 7~ have a nasty habit of losing a consid-: erable portion of their emission without warning, and a check of the kind méntioned should certainly be made from time to time.