Howling—and its Cause and Cure

Radio Record, Volume I, Issue 34, 9 March 1928, Page 3

Howling—and its Cause and Cure

Full" Analysis and a Reliable Test Outlined

By

M.I.R.

E.

ges] OWLING valves are the ‘| fei curse of radio broadcast rePal ception to-day, not only in: Hthe populated centres, but. ¥}eyen in the country, where sia single persistent offender can spoil an evening’s entertainment within a radias of 10 or 15 miles, and even more. WV ANY people are innocent offenders through sheer ignorance of the correct way to handle their receivers. It is surprising to find that numbers of good folk have entirely wrong ideas of just what causes howling, and although they are only too familiar with the effects of other howling sets on their own, they could not tell the symptoms of the same trouble being caused by their own apparatus. HERE was a classic case only a few? days ago, when an irate individual marched into a radio dealer’s shop in Wellington with a set under one arm and sundry accessories in the other, and slamiing the lot down, announced that he was through with radio for ever, because of a persistent howler who spoiled his entire programmes. The dealer handled him diplomatically, and after full inquiries had been made and the set reinstalled temporarily, it was found that it was the man’s own receiver. He had turucd the volume contro] full om and left it there, appatently determined that he was going to get his full thirty bob's worth out of the aeier. He got it, 400: Also his neighbours! A THORNY PROBLEM. iit howling valye problem is a thorny ong. It has been all over the world whenever broadcast stations have been opened, and remains so today, and will be to-morrow, too. All that can be hoped for is te keep it a minimum, but that minimum is of such a measure as to represent a workable value. There are many folk who advocate legislation designed to inflict seyere penalties on offenders, and others who would prohibit the sale of receivers capable of becoming a nuisatice. It may be said right away that legis: lation has failed miserably to do any good in other parts of the world. For instance, in Britain in 1922, regula- J tions were issued with the object of coutrolling the issue of receivers capable

of causing interference, but they were soon dropped because they were found to be unworkable, and in fact were uufair, as receivers of a given design, made professionally and turned down officially, were being pnt together priyvately by "‘backyarders’"’ all over the cowutry. THE LEGISLATIVE ASPECT. Tus same condition of affairs is in existence to-day in New Zealand. The Post and Telegraph Department Jiave done their utmost to regulate the sale of apparatus likely to cause trouble, but in spite of that there are types of receivers selling to-day in dozens, and even hnndreds, which are regular pests. ‘They fit the regulations, and that’s the end of it, and the beginning of trouble when they are sold to the average citizen. No blame is attacliable to the Department, because even with the most flexible of regulations there are too many factors to be considered in testing apparatus for the regulations to be anywhere near 100 per cent. efficient. As a matter of fact, the New Zealand regulations contain one clause referring to the necessity of an inductive coupling -between aerial and secondary tuning circuit, designed, according to popular report, to minimise the transference of energy from the receiver to the aerial, and therefore reduce the strength of the interference. This regulation, from a technical point of view, is merely coinical, oud has caused endless amusement amongst overseas manufacturers, who lave considered the possibility of manufacturing for New Zealand. Long may it remain in force! It has had the effect of blocking the dumping of cheap apparatus, and has compelled those folk who want to obtain sets of simall value to buy parts and put them together themselves, thus limiting the number sold. Overseas manufacturers have invariably been compelied to build machines of a more or less special design to meet the regulations, and invariably this has led to the production of a superior type of ontfit to their usual chean standard machities. Happily, the trend of design or home-made sets has been in the direction of crystal detec- | tors and valve amplification. This ar-| rangement can cause no interference, and is an ideal one from every point of view, especialiy for reliability: and — quality of signal reproduction,

DIFFICULT TO LEGISLATE IMPROVEMENT. Teo return to the question of iegis- ' Jation designed to prevent howling, it is interesting to note just low difficult it is to take any steps of value, Under the Act the operation of sets in such a manner as to cause interference is an offence. Stripped of legal language, and taking the moral meaning, that is what is meant. To obtain a conviction is a different matter. It is quite possible, from a technical point of view, to track an offender down, but it means having the proper equipment and personnel, both of which cost money, for a start. Having located a howler, presumably the next step is to invade the offender’s house in order to examine the setprovided, of course, that the Magistrate will not convict on the evidence of the direction-finder or other equipment used for location purposes. This sounds easy, but a lawyer would pick it to pieces in no time, and a psychologist would have plenty to say regarding the public indignation factor over the invasion of a house with or without a search warvent, even though the offender was found to have a 40-valve set! Multiralve set owners would have little sympathy to spare. of course, but then they are only a small portion of the total community. THE GOVERNMENT'S POSITION, HERE is innch speculation as_ to what the Government is doing with iis 5s. per license fee. Take 40,000 licenses at this figure representing £10,000 per annum, and allowing for only 15 inspectors throughont New Zealand at £333 per annum, half of this money is gone at once. By the time administrative overhead as well as the actual time of collecting and accounting for moneys right throughout New Zealand is taken into consideration, there is little left to play with. ‘The Secretary of the Post Office has already stated that this is so, and it may not he possible that furiher criticism on this point may sting the Department into showing the allocation of these moneys, when it will be realised that declaring active war against howlers is owi of the question. UNDOUBTEDLY the Department has fnll information regarding the ac-

tivities of the British Broadcasting Cor-_ poration in their endeavours to tackle this problem, and will thereby ‘know jus* how far active detection and dealing with offenders cau go with safety, aud hcew much must be left to the common sense and decency of the listeniug public once they realise the very simple fundamentals with respect to howling characteristics. Of course if a person deliberately makes his receiver howl there is no remedy except to wait for the inevitable occasion when he will be most interested in the clear reception of a particular programme and somebody else will innocently give him a good dose of his own medicine. MOSTLY CAUSED BY IGNORANCE. "THE majority of howlers are causing trouble innocently or carelessly. The former are casy to educate. The latter are harder because many of them* are cussed, As mentioned above, the remedy for the latter is a strong dose of howl: ing from somebody else providing they don’t retaliate by howling back deliberately. This is an insane course, because there will be one or two others immediately retaliate the same way, and the last condition will be worse than the first. THE WORST OFFENDERS. pe worst lhowlers are to be found amongst people using one, two, and ithree-valve receivers, especially those using the "three coil" circuit. This latter type of outfit is an ‘absoInte pest, because unless very strong signals are being tuned in, the receiver will always be made to oscillate, Even a skilled operator will do so, although trying not to. It is no use saying that this design should be s«bolished, because it is a cirenit of good efficiency for a small set. Users of it should he warned by dealers, and periodicals or books publishing diagrams of how to make up such receivers should instruct the makers how to minimise inevitable interference effects. TOO OPTIMISTIC. IRYING to "reach out’? is the reason underlying the generation of most howling. There are many am-

bitious or optimistic people in New Zealand to-day who advertise or buy single or two-valve sets guaranteed to get Australian stations. Some of them "get" Australia all right, but their neighbours don’t receive much while they are doing their "getting." What ig not appreciated by operators of howling sets is that, while their set is osciliating, it is certainly at maximum sensitiveness, but at minimum quality, and if they are content to listen to such tubbish then they are either insane or going insane, and should consult a doe tor immediately. An osciliating receiver cannot un der any circumstances give other than badly garbled’ results. Anyone who denies this statement has never heard even moderately decent signals, THE TEST FOR HOWLING. THE test for howling is simple, and is this. Slowly aiter one of the tuning dials of the receiver when the receiver is tuned to the station it is intended to listen to. If a whistling or singing note is heard, which varies in pitch as the diat is gradually turned, then the set is oscillating. If the signals (consisting of music or speech, etc.) show a maximum at one spot as the dial is slowly turned, and on cither side of ‘the maximum decrease to a vanishing point without sign of that varying note, then all is O.K. If close to a transmitter, a set will not show this whistle, because the influence of the transmitter keeps the receiver in step with it, and prevents the note occurring. Uuder these circumstances the set will not tend to juterfere with others, but will prevent reception of clean signals by the offending receiver itself. To stop oscillating or howling, move the yolume or reaction control until the wliistle vanishes, when the tuning dial is turned slowly. The loudest signals delivered in a clean tone will arrive just before the volume or reaction control is moved so far as te set up howling, If there is no method of controlling howling, owing to the machine being fitted only with tuning dials, see the dealer whe supplied the set at an early date and get his advice.