INVESTIGATION INTO FADING.

Radio Record, Volume I, Issue 9, 16 September 1927, Page 4

INVESTIGATION INTO FADING.

We are looking forward with interest to the results of the com- | bined inquiry into the facts of fading, which we are asking our readers to undertake with us on the evening of September 26 and 27; in relation to the transmission of 2YA. It remains to be seen just what facts can be established by the mass of combined reports we hope to receive. The scattered and individual reports that have come to hand previously in relation to 2YA have been of a most contradictory nature-some listeners reporting no fading, while others indicate intermittent and occasionally persistent fading. Obviously the fault must lie either with the transmitter, the receiver, or intervening factors covering atmospheric conditions, including magnetic storms, or atmospheric electricity, or land absorption. It will be very interesting to discover, if possible, which factor is primarily at fault. If the transmission is at fault, every effort will be made to effect remedy. If the fault lies with the reception, then it will be the duty of listeners, individually and collectively, to put their yeceiving sets in such a state of efficiency as to avoid reaction and annoyance to others. . . The comments that have been made in respect to 2Y.A recall the difficulty that was experienced in Great Britain following on the opening of the high-powered station at Daventry. Numerous and persistent complaints were then received from all quarters in relation to distortion, and an official article, published in the "Radio Times," dealt with the’ subject along lines that have an interest for New Zealand listeners. There were, it was pointed out, three possible causes. The first was fading, or what was commonly known as "night effect," which was described as being due to the confusion of those rays which travel tangentially to the earth’s surface, and those which are reflected downwards from a supposed electrified layer. It is not impossible that "night effect’’ -shoyld-be experienced during the day. A: second cause was land lines, which at times, due to intermittent earth or some other variation, might , give distortion. The third cause might lie cither in the transmitter or the receiver. The fading effect might begin to be apparent at 150 miles, and should be most noticeable at 200, 300 and 400 miles. There was no cure so far as the authorities knew. Theoretically, an absolute constancy of wave-length should minimise the trouble, and that was what was striven for. While this might not be always successful, the authorities thought that the average accuracy was so nearly constant as to prevent serious night distortion from this cause. As to leakage from land lines, the experiments carried out tended to show that this factor was immaterial. In relation to the transmission, the authorities affirmed that, with the greatest care, they could not suggest the fault lay here. Coming then to the conditions for reception, it was Stated that they had found quite definitely that, if the receiver was brought near to reaction, distortion did arise. Whether this was due to a partial fault in the transmitter-too much carry or too little modula-tion-had to be determined, but the fact definitely remained as a fact. It was admitted and emphasised that it was not always perfectly simple to get good quality out of Daventry, and the authorities were working hard to find out whether that was attributable to them. If it was, it would be remedied; if it was not, they nmst continue to press for sane methods of reception on the part of listeners. In that connection, it was absurd for listeners to endeavour to force sets to do more than they were designed to do, and too much reaction was always bad. It was pointed out that the reports received hy the authorities overwhelmingly showed that crystal users did not, on the whole, complain one-tenth as much as the valve people; and this was used in support of the theory that intensive reaction was spoiling results. Tt was suggested that some of those who had experienced trouble should try putting wp a much bigger aerial or a really efficient earth, until they were sure they were not relying upon intensive reaction. Jinally this review said: "We are all experimenters on the finer points, and can only go ahead in terms of co-operation and. frank speaking," " | We have summarised the British expérience hecause it seems to us to be applicable in some points to our own case. We have proposed this investigation in an earnest desire to secure a clear understanding of fading problems, and definite information, if possible, as to the incidence of the fault. We confidently look for the co-operation of our listeners. The investigation will be continued over two nights, and if required, we will not hesitate at a later stage to institute further tests, both in relation to 2YA and other stations,