RADIO NOTES

Dominion, Volume 27, Issue 68, 13 December 1933, Page 7

RADIO NOTES

By

CURRENT TOPICS

Listeners will be interested to know that Christchurch’s new station at Gobble’s Pass will be opened officially at 7.30 pan. on Thursday. This station will transmit on 720 kilocycles, having taken over 1 the wave length recently vacated by.2YA Wellington. Reports of the recent tests made by this station show that’ it can’be clearly received in Wellington with a notable absence of fading. The first speaker at the opening ceremony -will be Mr. I). G. Sullivan, Mayor. of/Chrlstchurch. He will be followed by the Hon. Adam Hamilton, “Postmaster-General. Both these speakers will have their speeches relayed to the studios in Christchurch from Parliament Buildings, Wellington. Further, speeches will be made by Mr. H. D. Vickery, Chairman of the Board-, and Mr, J. H. Owen, Chairman of the Advisory Council to the Board. One of the few giants of art who have hitherto given the microphone a wide berth, Paderewski, the beloved pianist, has apparently realised that he has a duty to that part of humanity who cannot attend his concerts in person. He may consent to broadcast in America this year, though he stipulates that he shall be “pub on the air” only for the last half-hour of one-hour concerts given in public. • I • • Reports on the recent wave length shuffle indicate that apart from a few minor matters the recent changes have proved to be satisfactory. So far as 2YA is concerned signals are obtaining a definitely better coverage. In the case of .one or two of the other stations there are complaints of jamming.' For example, some' listeners complain that 2YC on 840 kilocycles Interferes with 2BL Sydney. As there is a space of some 15 kilocycles between the'two stations. complaints of this nature come from owners of unselective sets.< The only cure is to make the set more selective either by using a shorter aerial or by adding a series condenser in ,the aerial lead in circuit. While on -the matter of selectivity it.is, perhaps, timely to.point out that the five new stations to be erected In Australia willhave a power of 20, kilowatts. This greatly Increased power will bring in its train further problms of selectivity not only in Australia but in New Zealand as .well; . . > • “ Interesting plans for. television are discussed in an official statement of the German .Post Office'. . At a conference held on October 16 between the German Ministry of Posts apd the Broadcasting and Television Authorities, it was stated that research is now to be concentrated on 180-line images with the retention of the present number of frames per second, namely, ; The existing high-power ultra short wave transmitter at Berlin is to be adapted to the new system and the work should'be completed within two or three months. In the meantime the television industry will produce a number of suitable new television receivers The second ultra .short-wave transmitter is to be used for the transmission of sound as well as vision, and this will be completed by April next, when the transmission of sound films will be-tried. The dispersal of the delegates.to the European Broadcasting Conference In Holland without final agreement creates a serious situation. There are rumours of reference to the Permanent Court of International Justice, but these can be discounted. The big countries will hardly take the risk of losing some of their channels, which would be quite a possibility if the smaller countries were able to state their case before an independent judicial tribunal. Possibly one final effort will be made through foreign offices. January is getting near, and unless agreement is reached there will be general chaos.

OPENING OF NEW 3YA

Special Section in This Week’s “Radio Record” The opening of the new 3YA station at. Grebbin’s Pass is the subject of a special section in this week’s “Radio Record.’’ Brightly written and excellently illustrated articles deal with various aspects of the new station, from both the technical and non-tech-nicaT angles, and there is also a brief resume of the history of the province of Canterbury. There are all the usual features, including notes from the main centres, a section for the technical reader, and Australian and New Zea* Iftng programmes for next week; in addition, there is the first of a weekly series of interesting talkie . notes speci; ally written for the “Radio Record” by a former Christchurch girl now living in Hollywood. In the women’s section, in' addition to the usual recipes, and patterns, is the first, of a number of articles on diet and health; ‘written by Mr. Ronald T. McLe’dn, well-known’ Wellington dietitian. ' *

RADIO ANNUAL

If, as the “Radio Record” suggests; a Christmas Annual should be like a good cocktail, the 1934 “Radio Record Annual” should have universal appeal. There is in it everything that could be found in a good cocktail except the after-effects. The stories in this annual are remarkable for their inspiration as well as for the fact that in practically every case they are written by local talent. Some of the verse, indeed, is worthy of pastmasters at the art; especially the winning verse concerning Mary and her little lamb. Those in search of technicalities will not find it in this annual. They will find, however, a .change from microfarads and megohms in a collection of playlets, short stories, and yarns that make .this, the first radio Christmas annual In New Zealand, almost certain not to be the last.' Here’s a novelty, indeed. On a ship outside the 12-mile limit off Los Angeles a new broadcasting station, RXKR, is operating on 815 k.c., with 10 k.w. In return for daily “boosts” of the Republic of Panama that country has given the ship the right to fly its flag—a clever idea on the part of the promoters. The idea behind all this is the sale of certain products which are advertised by RXKR and at the same- time pushed by salesmen ashbre.

“ ETHER "

FURTHER ADVANCE

Development of Television THE “ICONOSCOPE” An interesting step towards practical television was announced at a recent convention held in Chicago by the institute of Radio Engineers. It is tne development of the “Iconoscope ot Vladimir Zworykin relating to the use of a cathode ray tube in place of a scanning disc. ■■, The Iconoscope is claimed to be .several thousand times as efficient as the. scanning, disc even when it is working far below its theoretical maximum efficiency. It makes it, possible to transmit twenty pictures, or more, per second, with a detail corresponding to as many as 250 lines per square inch. The most important feature of the device, however, - is its power of Imitating the human eye in regarding a picture continuously and in possessing a certain degree of retentivity. It replaces mechanical scanning and several stages of' amplification; it is entirely electrical and has no moving parts. The • Iconoscope consists of two devices—a photoelectric mosaic on which the picture is focused by a lens system, 'and a cathode ray gun which fires at this screen a stream of electron projectiles. The signal plate upon which the 'picture is focused may be about 4 x-s..inches in dimensions and on its surface are millions of small photo cells, each consisting of a minute silver gjobule sensitised : by caesium. These minute photocells Uke a mosaic, arc deposited on an such as a thin sheet of mica, and the back of this plate is made conductive by a metal coating. Since both the photocell and the metal coating are conductors, and they are insulated from one another by mica, each individual photocell forms a' small condenser with the metal plate. T* 11 ? capacity amounts to several hundred micromicrofarads per square centimetre, and the sensitivity of the photocells is, equal to that of the modern caesium oxide type cells.

s DROPPING VOLTS I 1

Although it is easy enough to calculate the voltage absorbed in a resistance used, say, for the purpose of decoupling, those of us who do not shine at mental arithmetic generally have to take a pencil and paper to the task, at any rate if we are not dealing with round figures. The procedure, of course, is to multiply current, expressed in amperes or fractions of an ampere, by resistance (in ohms), the product being the voltage lost in the resistance. . ■ ■ ■ ■ ■ j ’ A handy rule to remember, and ohe that is applicable to most wireless receivers, is that each thousand ohms of resistance absorbs one volt at one milliampere. For example, a 1000-ohm resistor, passing 5 milliamperes, will absorb 5 volts. Take , another case that is likely to arise in practice: that of the anode circuit of a power-grid detector, estimated to pass 8 milllamps, and where it is desired to fit a 20,000ohm decoupling resistance. Applying the Simplified formula, we see that the voltage loss will amount to 20 X 8 — 160 volts. When dealing with bias resistances, it Is perhaps, more convenient to remember that 0.1 volt is developed across each 100 ohms for each milliamp, flowing in the circuit.