THE WIRELESS WORLD.

Otago Daily Times, Issue 19504, 12 June 1925, Page 2

THE WIRELESS WORLD.

CRITICISM OF 4TA. REPLY BY MR F. J. O’NEILL.

By Magna Vox.

Although local correspondence dealing with the merits or otherwise of station 4YA was closed on Friday last, Magna Vox has received an interesting letter from a correspondent in Wellington 'rim was not aware at the time of writing that the correspondence had been closed. Out of courtesy to the Wellington writer “Magna Vox” lias decided to publish his letter, which reads as follows: “Dear Magna Vox, —I have been much interested in the recent discussion of the quality of the transmissions from 4YA. but hitherto have felt that the subject is one into which “foreigners” like myself should hesitate to plunge. However, as comments by distant listeners have already been published, including some from Wellington, I would like to offer a few remarks. Mr O'Neill’s defence that those who are dissatisfied are suffering either from proximity -to the station or from the defects of their own sets will not meet the case. Here in Wellington. 4Yx\. is in marked to all other audible stations, and I think that the chief fault is over-modulation. There y a very simple and effective test on this point —an estimation of the strength ■>£ the unmodulated part of the transmission. It is, of course, well known that the “carrier-wave”'of a radiophone station is a continuous wave series of fixed frequency and amplitude. When this is modulated by speech or music or otherwise, the amplitude of the waves is changed, passing through a maximum ’ml a minimum phase for each cycle of the acoustic wave. But this has the effect also of modifyiiig the wave-length of the transmission. Taking for the sake of argument a transmission on 300 metres, which represents a frequency of one million cycles per second, modulated by a sound of 1000 cycles, we find that two new frequencies are produced, one of 1,001,000 cycles and the other of 999,000 cycles per second, and botli of these of course represent new wave-lengths—actu-ally about one foot shorter and longer respectively. Now the completeness of the modulation governs the amount of waveenergy which is converted to these new frequencies. An oscillating receiver tuned to give a certain beat note with tne original unmodulated carrier will give chat note with decreased strength as soon as the carrier is modulated; and if the carrier is modulated one hundred per cent, there will be none of the original frequency left, and the beat note proper to the 3bo-metre wave will bo inaudible, and will be replaced by new beat-note* due to the new frequencies. When a carrier is modulated by speech or music which generally consists at any instant not of one but of a great number of frequencies, the new frequencies on eacli side of the carrier are as numerous as the sound frequencies involved, and form a so-called “side-hand.” It is important to notice that all the energy of the actual sound transmission is concentrated in these side-bands. But they cannot oe made to contain more energy than there is in the carrier-wave to begin with; hence it is evident that the modulation must not be allowed to reach 100 per cent, except when the loudest notes are being transmitted. Now it is a matter of frequent observation here that during a transmission from 4YA, it is impossible to get a beat note at all with an oscillating receiver; that is to say. the output is being constantly modulated entirely into the side-bands. These side-bands will not produce a clear beat-note in an oscillating receiver because they are composed of a number of frequencies, and lb" beats are audible merely as a mixed noise due to a multitude of mixed frequencies. The output of 4YA is not only modulated by speech or music; it is heavily adulterated by “power-hum,” which may or may not bo due to the lighting of the filaments by alternating current as mentioned by Mr O’Neill in your notes of May 29. This, of course, subtracts energy from the pure carrier wave just as any other audio-frequency modulation does. * The amount of energy carried in this power-hum is far too large. One night recently I tuned in 4YA on a four-valve sot, and, with a little care, had the power-hum so strong that it rattled the diaphragm of an Aniplion loud-speaker against the magnets, and made a din that could he heard hundreds of yards away. Yet when the music was on, only very weak loud-speaker results of understandable quality could be had, because the sounds were unintelligible unless the receiver was markedly dc-tuned. These comments are forwarded to you, not in any unpleasant spirit of carping criticism, but in the hope that they may be of some value. I would like here to remark that to attempt to deal with a question of this kind by a count of letters for and against is bound to be unsatisfactory. Local experience has shown that a request for reports on a transmission invariably brings in a heavy crop of an considered praise, even, when the broadcasters have been well aware of glaring defects and have asked for reports simply in order to try to get a line on the faults. I think Mr O’Neill is to be congratulated upon his persistence and enthusiasm for broadcasting, and 1 should like very much to sec aim deserve all the praise that can be given to him for both quality and power of output. At the least, 'we might hope for as good transmissions as came from 4YA in the early days of the half-kilowatt transmission. But in all friendliness I would suggest that -Sir O’Neill should adopt another attitude towards his critics than mere ’ denial and refusal to admit the possibility of their having made reliable observations. The present poor quality of his transmissions is in fact a great disappointment to listeners here; and it must be recognised that some of those who complain have no trouble in getting excellent results from other stations.—l am, etc., H. Ilardcastle. Wellington, June 2.” MR O’NEILL’S STATEMENT. On Mr O’Neill reading the letter, he stated that prior to May 7 last he was using a reversed feed-back circuit for 250 watts. However, the Government regulations now in force lay down that the loose-coupler circuit is to be used. The reversed feed-back circuit is not a loosecoupler. After studying the matter carefully Mr O’Neill found that the best circuit to use was the master oscillator, which was the only practical circuit complying with the Government regulations. On changing over to this circuit it was found that it was very tricky to operate, and that there were many problems to solve. One of the principal difficulties was to get the aerial and oscillating circuits in tune, as a good deal of what is described by some listeners as "generator hum” is due to the two circuits being out of tune. The operators at 4YA, said Mr O’Neill, were guided to a very large extent by the reports of transmissions received from all over New Zealand and elsewhere, but it seemed that in some cases reception was perfect, while in other centres it was indifferent. In working a low-powered station frequent liberties might be taken, but on a high-powered plant the slightest adjustment would throw the transmission out of tune. Even one high note in a vocal solo sung very loudly would have this effect, and similarly a sudden sharp crescendo by an orchestra would cause the same trouble. Problems met in transmitting on a high power were never encountered when using low wattage. Another difficulty was that during the concerts the batteries discharged at the rate of 45 amps, an hour, and no batteries would stand that for long. This problem had been partially solved by putting in a large outfit 'of batteries. Then, again, there was 1500 volts on the plate supplied by Waipori, and if Waipori failed, Station 4YA would fail also. On applying alternating current to the filaments another difficulty was encountered, as a more induced hum was the result. It was then found that 1o got everything clear a big mechanical job was entailed in moving all the part? of the set susceptible to induced alternating current out of range, which resulted in the balance of the set being upset. Then, the ruicrouhones commenced to “howl” when the alternating current was brought near t.iem. The operators were mastering the problem ae

rapidly as possible, and they claimed that a solution was now not far away. In conclusion Mr O’Neill said: “We have gained knowledge through lengthy experience, and have travelled a path which others will have to follow. They will have the same conditions to comply with, and will find that many people are under the delusion that when any set is installed all they have to do to obtain fine transmissions is to simply turn a dial as a tap is turned when water is required. We are mastering a very big problem which few in the dominion have tackled. With all the criticism, if anyone in New Zealand can give us any points or demonstrate that they can do better than we have done, all facilities will bo given them as well as' every assistance. We will place the station at their disposal and let them operate it, or act and be guided by any sensible suggestion in order to perfect transmission. ” Mr O’Neill then demonstrated that the resonance which amateurs contend is due to “generator hum” was caused by the aerial and oscillating circuits not being synchronised. [Paragraphs in other papers show that criticism of other New Zealand stations and the two Sydney stations is general at the present time.] 2FC, SYDNEY. Messrs Farmer and Company, Station 2FC, Sydney, hove arranged with Madame Elsa Stralia, the world-famous dramatic soprano (whose concert tour of Australia and New Zealand has commenced) to sing at the Sydney Town Hall on Wednesday next in connection with the presentation of prizes to the winners of the Radio Voice Competition, organised by 2FC. The competition was open for 10 days, and 1035 entries were received. Prize money to the extent of £205 will be distributed. New Zealand amateurs will doubtless readily avail themselves of the opportunity of hearing Madame Stralia. by wireless. The concert has been organised by Farmer’s Broadcasting Service, in conjunction with the Evening News. Magna Vox will welcome reports of reception. The concert will commence at 8.30 p.m., New Zealand mean time. The following programme has been arranged : 8.30, band concert; 9.0, Miss Lilian Frost will render selections on the grand organ ; 9.30, arrival of the chairman; 9,32, 2FC Studio Choir (conductor, Mr W. Bourne) will sing; 9.37, 2FC Chamber Trio: Mr Gladstone Bell (cellist), Mr Lionel Lawson (violinist), Mr Lindley Evans (pianist); 9.45, Mr Robert Gilbert (baritone), winner of the first prize for men in the Radio Voice Competition; 9.51, Mr Lionel Lawson (violinist) ; 9.57, Miss Essie Watson (soprano),' second in the women’s section of the Radio Voice Competition; 10.4, Mr Harry Thomas (elocutionist) ; 10.12, Mr Reginald Lawson (tenor), second in the men’s section ci the Radio Voice Competition; 10.8, the Russian “Bnllakuka’l Orchestra (first appearance in Australia); 10.28, Miss Muriel Humphries (contralto), winner of the first prize for women in the Radio Voice Competition ; 10.35, Mr Gladstone Bell (cellist) ; 10.41, Madame Elsa Stralia : (a) “Bel Reggio,” (b) Easter Hymn (Cavalleria Rusticana) with 2F'C choir and grand organ ; 10.53 presentation of prizes to the winners of the Radio Voice Competition, the two winning teachers, and the winners of the public voting section; 11.5, the hand will play; 11.10, Mr Harry Thomas (elocutionist) ; 11.18, Mr Lindley Evans (pianist) ; 11.28, Mr Robert Gilbert (baritone); 11.52, the Russian “Ballalaika” Orchestra; 11.42, duet, Madame Einy Marks and Signor Cncialla (the winning teachers); 11.48, Miss Muriel Humphries (contralto), “Land of Hope and Glory”. (Elgar), assisted by 2FC choir, the grand organ, and the Radio Voice finalists; 11.58, National Anthem; midnight, close down. At the piano, Mr Ewart Chappie; at the organ, Mr James Brash. Mr A. S. Cochrane will be the announcer, and Mr Oswald Anderson will direct the proceedings.