WIRELESS NOTES

Evening Star, Issue 18256, 21 April 1923, Page 11

WIRELESS NOTES

ADVICE TO EXPERIMENTERS. LOUDEST SIGNALS HERESY. [By Electron'.] When tuning in signals, especially speech or music, do not make the mistake o: trying la gei ih» .-.igads in the loudest possible. This is me most frequent fault of the experimenter, and it ieaiiy spans the fun for the rest oi tho listeners. The regular radio eutausiast’s greatest achievement, in his own mind, i„ in getting the signals the loudest possible. iJ-o does not pay any attenuon to what is being .said or sang .or played by tho broadcast;m. stations, but ins every effort is dir. cud towards getting the loudest signals. He tunes m the music so loud u.-at, it sounds like a mixture of a storm and a railway train passing by, to 'tho accompaniment of a few roosters crowing and a thousand life and drum oo;ps, all going at the same time. And then tho listener wno has never heard the radio before says; Well, I admit it is a wonderful thing to think that you can get anything at all out of the air; but give mo my V'ica'ola."

Tliis is all wrong, because die music scut out via. radio can La repieduced with all the clarity of the original spoken word; or the notes of the (lute or whatever mu.-ic is being transmitted can Lo reproduced with true and faithful rendition, so that the repeated sounds will hardly bo distinguished from the ormnal.

So do not make this great mistake and take all the fun out ot receiving, especially if you have a regenerative set. The regenerative set, though it is a wonder for amplifying and bringing in loud signals, is the worst offender when it conies to distorting signals if the operator does not guard against the ; erupts tion of tuning in tho sig.-al too loud. When the novice starts tuning a now regenerative receiver ho usually gets all kinds of squeals, squawks, and grunts, but no signals, and then he blames it on the receiver. He goes back to the manufacturer and complains that he has been cheated, lie claims that the thing does not work, did not work, and never will work. Tho sot is then tried out by the manufacturer or dealer and found to be satisfactory, and the dealer then says ho will nob take it back, and so on. The trouble in nine out of ten oases lies with the purchaser. Not that it is wholly his fault, bub he either docs not rig up the set correctly or does not understand how to operate it. Most of the howling, squealing noises are caused by tho novice operator turning the regeneration dial around, so far that tho detector vacuum tubs starts to oscillate and to produce oscillations that combine with the incoming signals, and start a squeak. Learn to operate your set before you pronounce it “no good.” Invite some friend or some friend's child who does understand radio and the operation of tho radio sots, and Itave them show you and give you a few lessons in tuning. It is certain that you would never think of purchasing an automobile and getting in and starting to drive the thing home if. you did not know how to drive. You sm - cly would not think of fooling with the levers and switches on the car in the hope that you would pull one or push one that would start the car on the way homeward. Tliis would bo foolishness.

Then do not expect to got results from your radio set until you understand at least what tho different knobs are for, and have had a little practice tuning-in tho different wave-lengths. “ Practice makes perfect ” in radio, as in everything else.

The lead-in wire should not bo run long distances through the house, as the electrical capacity between the wire and the walls or ceiling will have an absorbing effect which wifi cut down the strength of the received signals.

If amplifying transformers are mounted close together in a set, place them at right angles to each other so that the magnetic fields of each will not bo in the same direction. This will -prevent magnetic coupling) between tho different stages. If this precaution wore not taken, the amplifying circuit would most undoubtedly “howl” or make queer squeaking noises.

Do not crowd the instruments together to make.the set compact. This is sometimes the only thing that prevents a beginner’s set from functioning properly. The instruments are crowded together so close that they interfere with the working of each other. This interference wo are speaking about, of course, is an electrical interference and not a mechanical one.

If tho set uses a storage battery, get a good one of standard make. -It does not pay to obtain a cheap storage battery, because if it is cheap you may depend it is not of such good quality, and will cause trouble in the long run. The host storage battery is the best battery, and in spite of the higher initial cost you will make it up in a short time in satisfaction; whereas if you get a cheap one you more than probably will be sorry in a few months. Be sure to handle your vacuum tubes with care, or you will regret it. Tho filamont of tho tubes is the same as tho filament of the electric light that you use in your homo to give light. If you bounce one of them on tho table you will bo likely to damage tho filament—break it, in other words—and you will bo “out” tho price, of a tube.

Tho samo applies to the telephones. Handle them with care. The telephones contain a permanent magnet that will ho affected by any sudden shocks. A permanent magnet loses its magnetism upon being struck a sharp blow, such ns being dropped on the floor. This decreases the sensitiveness of'tho telephones, and every time they are banged around they lose a certain amount of their original sensitivity. A good' way to test out an amplifying transformer to find out if it is opencircuited is to connect one end of the winding to one terminal of the head telephones. Then, with the telephones on the ears, touch the other terminal to a dry cell which is connected to tho other end of the winding of the transformer. If the transformer winding is 0.K., there will be a clicking noise heard in the telephones. Then try the same thing with the secondary winding of the transformer. If no clicks are heard, one of the windings of the transformer is '‘open.” A grid leak may be made by cutting a piece of cardboard into a piece about lin square, and then covering it with a uniform layer of India ink. After it has dried cut this piece in half and boro two holes in one of the pieces half an inch apart. In these holes insert brass 6-52 machine screws, flat-headed, and fasten them tight with nuts on the ether side. One screw' will be the terminal and the other screw will be the other terminal of the grid leak, while the India ink will form tho resistance. This resistance may be varied by cutting the strip narrower and narrower, while listening after each cutting to see if tiro signals are getting weaker or stronger with the changes in resistance. A record can be kept of the different widths, and then, when the maximum results are recorded and further cutting begins to decrease the strength of signals, the second piece of cardboard can be cut to the correct size, and the grid leak connected to the set for permanent use. The grid leak can either be connected across the grid condenser or from tho grid of the tuba to the negative filament connection. Tho sensitivity of an audion tube may sometimes be increased by placing _a large horseshoe magnet in a certain position so that the poles of the magnet are on each side of the tube. This probably is due to the magnetic effect upon the moving electrons flowing across from the filament to the plate. The amateur experimenter will find this a good field for him to investigate, as ho may hit upon some new idea along this line that will ho an improvement upon the present-dny vacuum tube. Needless to say, if this should be the case, his fortune would) bo made. GENERAL NOTES. In our report of the long-distance reception at Mr I. S. Macdonald’s station nt Waiwora South we omitted to mention that Mr 0. Railton, who is well brown amongst wireless experimenters, was working with Mr Macdonald, a great deal of the apparatus being constructed by himself, their results being obtained by both experimenters working conjointly. We have been advised that there is every likelihood of a broadcasting station equal in power to the local station being installed at Wellington very shortly. With a further station installed at Auckland, there should be no lack of entertainment this winter, a three-valve set being capable of tuning to any of these stations.