Radio Broadcast (May 1928-Apr 1929)

AUGUST, 1928 WHAT (JAN WJb, SHE dY RADIO : 187 screen, judging from the fact that in a demonstration a slight yawn on the part of one subject caused his face to drop off the screen. Actually, no proponent of the new art seriously contemplates this type of broadcast. Every one of them has in mind transmitting, not from living images, but from photographically recorded cartoons, using outline figures and silhouettes of the type shown in the comic strips. With these some degree of motion can be seen and the figures themselves can be so different in outline, as in the case of Mutt and Jeff, that the observer will be able to follow the action. You can tell whether little Jeff is leaning disconsolately against a lamp post or sitting at a table taking refreshment, but it will not be possible to distinguish whether Mrs. Mutt hits her distinguished husband with a rolling pin or a frying pan. You will be able to see the hit but not the sparks nor the lump that grows on the bruised spot. Knowing what is being sent, how it is being sent, to what degree it will be received under the best conditions, and how to receive it, still leaves a good deal to be said. Nobody at this moment knows how satisfactory home built apparatus is going to prove, or how the broadcasts are going to go over in the face of possible static and other interference from internal and external sources. We do know that even mechanical vibration of the receiver makes the screen blank. In that particular, we recall the old cat's-whisker-andcrystal days when every member of the household had to sit rigid and hold his breath at the moment of an announcement. The rumble of a truck or the passing of a trolley might upset the sensitivity. All this is true of such home-built apparatus as has come to our attention. It may be equally true of commercially built receivers. The problem of synchronization is not solved in any commercial type of apparatus yet disclosed. The best that any manufacturer contemplates is manual speed control of the motor. This is a hand operated rheostat, and it needs but little imagination to see that it is very difficult to hold the image in this way for more than a fleeting glance now and then, especially if the line voltage variation or fluctuation is very frequent. I am inclined to think much better results could be obtained with a six-volt motor on a storage battery. Any fan could do that, of course, as the particular source of the energy which turns the disc is of no importance. Even a spring motor would work if the speed were great enough, the power sufficient, and the period of operation long enough. I am informed that at least one manufacturer plans a device fixed automatically for only one speed, being even more accurately governed than a phonograph. Any variation in speed is detected by observing a second neon lamp through an auxiliary spiral of holes in the scanning disc. Personally, 1 have confidence only in the establishment of a synchronizing station, perhaps one of the smaller ones forced from the broadcast field under the new law. For the television camera described by me last month, such a station sending constantly a 10-cycle sideband or a 1000-cycle sideband, or both, would not only take up little room in the spectrum, but furnish synchronizing means to transmitter and receiver alike. Such a station might well be RADIO ROW SEES A NEW BOOM Down in New York's Radio Row, the crowds are thronging in the old 1923 fashion. The reason is apparent in the arrow-shaped sign at the top of this picture subsidized by the larger ones and, moreover, would tend toward standardizing the speed of all receivers and prevent the growth of a multitude of separate forms of transmission which ultimately must be brought together. Sooner or later the purchaser will demand that his receiver be such that he can get any image broadcast. Imagine any radio receiver manufacturer trying to merchandise nationally a radio set which would receiveonly one station or one fixed wavelength! Yet that is just what the televisor producer plans to-day. The cost of the commercial television attachment for a radio receiver will run to about $150. That means home-built apparatus for most fans. He jean buy a first quality neon tube for $12.50, with the promise that this will go down to about $7.50 as soon as there is a demand that warrants a quantity production. The motor will cost from $9 upwards. It need not be over g-horsepower and, if belted to the disc, even a smaller motor may be suitable. The big difficulty will be in getting a suitable disc, unless manufacturers wake up to the fact that this piece of the apparatus must be of a high degree of accuracy. The cost of a suitable aluminum plate with the spiral holes cleaned out and countersunk will be quite high but well worth while in comparison with the paper discs now making their appearance in conjunction with a little neon night lamp now being widely sold for television purposes — for which it is worthless. This little bulb is good, however, to indicate whether you have a.c. or d.c. current, as it glows on both plates only with a.c. Direction W = H A SCANNING DISC LAYOUT FOR WGY RECEPTION The number of holes in the disc is determined by the constants of the apparatus at the transmitting end — 24 holes is the correct number to receive the pictures beings transmitted by wgy. W is the width of the picture and H is the height of the picture as it appears to the observer, the shaded portion therefore representing the actual si{e of the picture received with a disc of the above dimensions.