DOUBLE YOUR RADIO’S VALUE

Evening Star, Issue 23723, 2 November 1940, Page 4

DOUBLE YOUR RADIO’S VALUE

CONVERT IT FOR PLAYING RECORDS

Your radio set can double its value if you use it for record reproduction. Most good radio sets are capable of being used with a gramophone pick-up, which transforms them into electric radiograms. Of late years the sale of gramophone records has increased tremendously. People are buying records in greater numbers than ever before. As a matter of fact, the gramophone industry must acknowledge its indebtedness to the radio science because it was the introduction of electrical recording, and, later, of electrical reproduction, which revolutionised the record business. The old acoustic gramophones and recordings were suffering from primary disadvantages which rendered many things difficult or impossible. Frequency range was very restricted, volume control was difficult, elaborate and expensive horns were required for anything like decent results, and so on.

When electrical recordings and reproduction came along the big impetus was supplied, which changed the whole face of the industry. The first electrically recorded records to be released caused an absolute sensation among gramophone lovers, and when played on electrical machines one began to wonder whether an improvement was possible. It was possible, and it was made. To-day the modern electric machine reproducing one of the latest and best recordings ip really a marvellous thing. Our problems now are as much those of the surroundings in which the machine is placed as of the machine itself.

A radiogram is a good radio set which has a pick-up attached to it. The output from the pick-up can be switched through the audio section of the set, which, in turn, reproduces the output from the pick-up just as it did the output from the tuner. In the one case the broadcasting station feeds the audio section, in the other the pick-up serves instead. When the pick-up is in use t}ie radio side of the combination is not doing any useful work at all. The output is simply an amplifier and a speaker connected to a pick-up. Naturally, a good amplifier section is essential if good record reproduction is required. If you cannot get good tone and volume from your receiver, because it is a small one, has a poor speaker, etc., you naturally must expect these disadvantages to apply equally to record reproduction. On the other hand, if you have a radio which is fitted with a big speaker, push-pull output, and plenty of volume and tone, it is reasonable to think that you will get excellent results when a pick-up is used. The reason for insistence on plenty of output and volume L That most people tend to turn up their gain control on records 'more than they do on radio. As a result, they are apt to be disappointed if the set “ won’t take it,” The quality of your best radio reception is a good guide to the quality you can expect from the pick-up.

Most good sets these days have a pair of pick-up terminals at the back of the chassis into which your pick-up will be connected. If such terminals are not there it does not mean that the set can’t be used with a pick-up. But it does mean that, if you fit a good pick-up into the terminals on a set provided with them, you can expect good results. They would not be therd otherwise. In such a case it is highly probable that the volume control on the set will also operate on the pick-up. This is an important point, as it is quite essential to have some means of volume control from tho pick-up. Otherwise, you are quite certain to overload the set, with the full output of tho pick-up always applied. If by some means you should find that the volume control on the sot does not control the pick-up, you will have to provide such a control. This is very simple to do and tho connections are easy.

For a magnetic pick-up a control of about 50,000 ohms will do—a crystal pick-up needs ono of 500,000 ohms. Both controls will bo potentiometers. The pick-up leads are connected to the outside terminals on the potentiometer. It will have three terminals. Tho leads to tho sot will bo made, one from the centre terminal of these three, and one from the terminal to which you have attached the earthed lead of the pick-up. This will usually be a black one. Tho other, or “ hot ” lead, generally is red, or has a red line woven into its insulated covering. Some pick-ups have three leads instead of two. The third lead is to be connected to earth, and in the above case is attached to the terminal on the potentiometer we have regarded as earthed. There thus will bo two leads from the pick-up connected to one terminal of tho potentiometer. Some pick-ups already have a volume control built in. This is convenient, and avoids the extra fitting, should it be required. As a rule, the average set has enough gain to operate.from the average medium-to-high output magnetic pick-up. The crystal type has a much larger output and the. only thing to watch here is that there is at least 250,000 ohms total resistance connected across it. Most modern sets allow for this, but many three-year- fid sets (or still older) are not suitable,for use with these pick-ups. Consequently, unless you get expert advice, do not fit a crystal pick-up to an old-type receiver. You must, of course, have a motor to turn your records round. An old-type gramophone will probably do this'" quite well, unless it is.an ancient one, with very little power. As a rule, portable gramophones have motors too small for the job of pulling the modern record, but the better-class of acoustic gramophone, with double or treble spring motor, is suitable. The electric motor is a great convenience, and yoii will not have to keep winding up between records. You must get a good electric motor, as a bad one is worse than useless.

In WLWO, one of the most powerful stations in America, the letter O, last in the station identification, was chosen for a special reason. O is one of the easiest letters to form in any language, and sounds nearly the same in all of them. At the same time the WLWO call letters ■were assigned, all the mobile unit and relay licenses were changed. Each transmitting device, from pack short wave unit to mobile unit, is a radio station in its own right, though used only for relay purposes, and must be identified, engineers explained. WLWO (under the name WBXAL) began operation in 1924, and is one of the pioneer international broadcasting stations of the world. The frequencies at which it operates are 6,060, 9,590, 11,870, 15,270, 17,760, and 21,650 kilocycles.