ON THE AIR

Hawera Star, Volume XLVI, 9 April 1927, Page 18

ON THE AIR

(By "Wave Length.")

"Wavelength” invites readers to forward short accounts of their experiences In reception, In overcoming problems of construction, and Items of Interest on any subject likely to Interest their fellow radio enthusiasts.

By this time all owners of receiving sets should be in possession of this year’s radio license. The authorities responsible did not want us to forget about the 30s, and so circularised each owner with u polite reminder. However, we must realise how cheap the programmes amount to nightly.—less than one penny—and the standard of tiie broadcasts has been very good.

In an ever-increasing number of homes throughout the world radio is becoming one of the essential features of the family life; whether as a form of entertainment, or on behalf of its usefulness in bringing the latest news of markets or weather, depends entirely on the habits of the particular home. Until recently it was the hobby of one or more members of the family, now its appeal is general, and the result of this change is an increased demand for complete receivers, so designed that they require little or no skill for'their operation. For the most part these receivers are required to reproduce faithfully all musical notes, and the purchaser ofttimes expects to be able to distinguish one instrument from another in a full orchestra.

In the new Sydenham Hospital, New York, which has just been erected at a cost of £500,000, provision has been made for a radio system that will supply patients of the institution with broadcast entertainment. This probably is the first time that a radio installation has been incorporated in the architectural design of a building, and for which the details of a radio system have been considered as a definite part of the building plans.

A well-kept battery needs only charging and a monthly addition of distilled water. This distilled water may be purchased from any battery charging station or may be made with improvised equipment found around the kitchen. A kettle of boiling water, a length of clean rubber tubing, for fitting over the spout of the - kettle, a clean glass jar, and a pan of cold water constitutes the “laboratory equipment” necessary to produce distilled water. This outfit should be assembled as follows: The kettle of water, with the robber tube fitting tightly over the spout, is placed on a gas ring, and the glass jar or jug placed in the pan of cold water—the level of the water, of course, being below the top of the jar. The free end of the rubber tube is then placed within the iar : about Jin from the bottom. The explanation of the action of this plant is as follow: The steam passing from the kettle and through the rubber tube strikes the cold atmosphere in the glass jar and is condensed to water. This water, carrying no impurities with it when in the form of steam, is the distilled water used for batteries. .Enough of this water is added- to the cells of the batterv to keep the plates covered with at least a half inch of the water. Always add water before charging rather than after charging, because if the latter course is followed the hydrometer will show a lower reading than the true state of the battery. Adding the water before charging gives it a chance to become thoroughly mixed with the other electrolite. A hydrometer. which is indispensable in home "barging, will give the reading at different points of the charge, and determine when the battery is fully charged.

A hydrometer is a glass syringe- having a rubber suction bulb at one end and a flexible rubber tube at the other. Inside this syringe is a glass float weighted with -shot at its lower end; the tipper part of the float is calibrated and marked for taking readings. To take a hdyrometer reading draw enough of the solution in the hydrometer so that the float floats freely. The reading which comes level with the top of the liquid in the hydrometer gives the state of the charge, which is somewhat as follows: 1275, fully charged; 1250, 80 per cent charged; 1225, 60 -per cent charged; 1200, 40 per cent charged; 1175, 20 per cetn charged; 1150, exhausted. When the test- shows a reading below 1200 it is time to give the battery _a, recharge until by successive readings of the hydrometer it shows full charge. The theory of the valve is briefly as follows: (1) Small currents from the aerial are passed through a. step-up transformer so as to produce a-s high a voltage change as possible, an-d led to the grid. (2) Yoltage changes on the grid produce enhanced currentchanges in the plate circuit. (3) These enhanced currents are passed through another step-up transformer. giving higher voltage "fluctuations. These are impressed on the grid of the next valve, and so on till the final circuit with its loud speaker and power valve is reached. There are then three elements in a valve, three, associated circuits*. and two. sometimes three, batteries.

It is estimated that there are now about- 20,000,000 people listening regularly to radio broadcast -programmes in the United States, an-d it is- expected. at the present rate of “hooking up.’’ that- the number will .be 28,000.000 at the end of the present- year, with the gradual reduction of the cost of receiving sets -below the presentminimum of £1 per set. This has created a serious congestion in the air. There are 700 broadcasting stations competing for the favour of the radio audience in t-he United Statevs. It is impossible to find a wave length that is not being used by half a dozen stations, while many of them are serving fifteen or more' stations, some of which are too close together. To meet the difficulty of congestion in the air, a new science, that- of electro-acoustics, has sprung into being, and is devoting itself’ to the task of clarifying programmes where'they overlap through the multiplicity of wave-length users. Already some advance lias been made in handling sound in the air. Microphone teehnimie has been improved to the extent that not only the middle register, but the high notes and low nates of music, can be handled by the microphone Modulation -systems have been worked out bv which distortion in radio transmission if? being gradually eliminated.