OVER THE AERIAL.

Waipa Post, Volume 47, Issue 3359, 26 August 1933, Page 4

OVER THE AERIAL.

(By DXI66A.)

QUESTIONS AND ANSWERS

I have an aerial 30ft high and 90ft long, including lead-in. Is this satisfactory?—Yes? Ample for all you requrtrc. I have built a special two-valve circuit but am unable to get the set to oscillate on frequencies between IYA and 3YA] —Take off fcur or five turns from the aerial coil. A WARNING TO CONSTRUCTORS. Powerful permanent magnets as used for moving coil speakers or electro magnets such as MC pot windings create strong magnetic fields in the space around them, and therefore are to be shunned while wearing a delicate wristlet watch, which may easily become magnetised.

RADIO ADVERTISING

AMERICAN OPPOSITION. The sixteenth annual session of the American Association of Advertistising Agencies favourably heard an advertising policy in radio, encompassing the air, newspaper and periodicals. The plan is as follows: Elimination of offensive and lengthy trade announcements in radio advertising programmes. Inclusive national schedules for newspaper-radio advertisers, whereby each form of advertising shall be " geared in " with the other. Co-operation, rather than hostility, between the radio and the nation's daily and periodical press. Delegates heard the result of a survey by Frank A. Arnold; former executve of the National Broadcasting Company, and now vice-president of Albert Frank-Guenther Law, Inc., advertising agency. Mr Arnold's survey showed that radio listeners-in are evidencing cumulative offense at long-drawn-out, intrusive and irrelevant " ballyhoos " in the midst of radio entertainment. Speakers at the convention here pointed to a sharp decline in advertising revenue of the two older broadcasting chains during the first quarter of 1933, and ascribed it in part to the " ballyhoo" tactics of some radio sponsors. " Why does the advertiser," asked Mr Arnold, "tell his story so well in newspaper print in 200 words, and yet require 600 words when he tells it on the air? " He cited a 725-word commercial radio "ballyhoo," adding: "After the first 200 words all interest was lost."

RADIO JOTTINGS. Detectcr or audio stages in which fairly high anode resistances arc used will always need far more " B " voltage at the battery plug than it is intended to apply to the valve, owing to the drop in Voltage across the resistances. Sensitive measuring instruments should not be placed close to powerful motors,, dynamos, loudspeakers, or eliminators, as they may easily be seriously impaired in this manner. If you cut off a piece of cardboard strip of suitable length and push a small screw through it, the cardboard strip will enable you to hold the screw steady in what appears to be an inaccessible position while you are operating the screwdriver. Ilf you are employing a neutralised R.F. stage, do not forget that this will need re-neutralising if a different valve is employed for it. If you are using a screen-grid set and have a variable high resistance on hand, try connecting this in the B plus lead to the screening grid, as very often a fine variation of the voltage

to this point gives improved results. Owing to its fairly high anode consumption, a pentode cannot he used successfully with small batteries but shoulld be run from the mains or from batteries of the large-capacity type. If a small disc, such as a cigarettetin lid, is threaded on to the aerial just before it -reaches the lead-in tube, the rain running down the lead-in wire will be diverted at this point, and, therefore, the insulation across the lead-in tube will be improved. An ordinary on-off switch fitted across the terminals of one loudspeaker wired in series with another will enable it to be switched into circuit withouit affecting the other speaker. For " family " use one of the permanent types of crystal detector "K generally more satisfactory than the " cat's whisker" which easily gets out «f adjustment.