RADIO RECORD

Greymouth Evening Star, 7 May 1931, Page 4

RADIO RECORD

NOTES FOR USTENERS-IN

(By

“Reception")

HOME RECORDING.

NEW RADIO DEVELOPMENT

Home recording, with home broadcasting as a side line, will he widely featured in the 1931 radio merchandising activities, writes an expert in “Radio Engineering.” As a built-in feature and as an accessory, it will bulk large in the coming season’s sales. It is a natural evolution. The engineering has been fully consummated. It is a direct challenge to the further invasion of the midget set into sot sales since it provides so much more entertainment as to make the saving of the former hardly worth while.

•The two great criticisms heretofore launched against radio are thrown into the discard by home recording. It has been claimed that, unlike the phonograph, radid has not been selective iri the sense of choosing definite programmes. True, one might choose between’ stations, but the choice was relatively limited in contrast with that afforded by a fine record library. And it has likewise been said that, unlike the pianp or violin, radio has afforded its owner no job nor satisfaction of self-expression or creation in the programme enjoyed, which has always been an important factor in home entertainment. ' ‘

J Home recording, of course, presupposes the inclusion of a modern electric type of phonograph, preferably as a built-in feature of the radio-set. And this is reasonable, for the trend is more and more toward combination sets, especially in meeting the competition of the midget ,radio sets. Home recordinig, therefore, by insisting on the phonograph feature, makes possible the repetitive enjoyment not only of usual records, but also of fine radio programmes which’ have been recorded by the set itself. The homd-recording feature is based on the simple principle of reversing the! operation of the usual electromagnetic pick-up. Instead of driving the pick-up by the action of a stylus or fieedle following the contortions of the record groove, thereby generating the modulated current that eventually drives the loudspeaker and reproduces recorded 'sound, in home recording the electro-magnetic pick-up is fed amplified sound values either picked up by a microphone or by th#- radio receiver itself. Under the influence of the powerful input ’ current, the electro-mag-netic pick-up actuates a blunt point' chromium-plated recording needle which- engraves that latent sound values in a special record. The metal records are pre-grooved, so that the cutting stylus follows the spiral groove and simply engraves the sides for the latent sounds. Several radio sets have already appeared on the market with home recording as an integral feature. The home recorder may be set either for the recording of home talent or for radio programmes. In the former instance, the hand microphone is connected in circuit, a blank record placed on the turntable with cutting stylus held just over the beginning of the groove, after which the turntable is started. The pick-up is weighted down with a special weight used only while recording. When proper turntable speed is attained, the stylus is lowered to the starting point on the record. The sounds to be recorded are then directed into the microphone until the end of the record is reached.

' For recording broadcast programmes the desired programme is tuned in to utmost clarity and the greatest possible undistorted volume. A blank record is placed on the turntable, and the turntable started. When it attains a steady speed, the pick-up with special recording needle is lowered to the beginning of the record groove. The proper switch is operated so as to transfer the receiver output from the normal loudspeaker function to the recording circuit, although the programme may usually be heard faintly during the recording. Thus the radio programme is recorded. The home recordings may be played on any phonograph, either electrical or mechanical, in the usual manner, except that a special fibre needle is employed in place of the ordinary phonograph needlle since the metal disc, is necessarily softer than the usual commercial recordings. When playing back the record on the same machine on which it was recorded, the recording weight is removed from the pickuphead. The home recording accessory may be pmployed with any phonograph turntable. It comprises essentially arecording head actuated by the radio amplifier, a microphone, and the necessary switching mechanism. In some designs a mechanical feed is employed to track the stylus in the groove, reducing the latter of this strain. An elaborate feed mechanism is attached .to the shaft of the turntable. Home recording is entirely practical. Several manufacturers are already merchandising combination sets with the home recording feature, while an even greater number of manufacturers are on the market with home-re-cording accessories for use with any existing radio set and phonograph. It is the writer’s opinion that this season will see a number of combination sets on the market incorporating this feature, selling for £4O to £BO, and placing the standard console once more on a pedestal with the midget sets shringing into insignificance. Meanwhile, the. special metal discs are available, to anyone. One organisation is now licensing and selling these records to distributors of the various manufacturers of home recordingequipment in four sizes, namely, Bin., 7-iin., 10in„ and 12in. The discs play on any phonograph with a fibre needle, and will reproduce indefinitely.

RADIO MUSEUM. The German radio industry has undertaken the task of establishing a national radio museum in Berlin Displays of transmitting and receiving apparatus dating from the .inception of public broadcasting will form the main feature of the museum, while a room is also to be set apart for busts of leading German experimenters and inventors. For many years pasf in England the Science Museum al South Kcimiugtun, London, has been building up on the same lines a, permanent record of Britain’s predominant contributions to the science. In addition to preserving examples of the earliest apparatus developed, the museum con A

PROGRESS IN TRANSMISSION.

Improvements made in the technique x of radio broadcast transmission, during the past year necessitated some radical departures from existing practice. One of the most notable of these is the tendency to discontinue small relay stations working from the main broadcasting transmitters, and replace them by high-power regional stations capable of producing substantially constant field intensities oyer large areas. On account of the high power of these stations it has been necessary to make provision against, needless interference between stations. Interference arising from departure from the declared wavelength has been minimised by the provision of suitable constant frequency drives for the transmitters, and the adoption of harmonic attenuation filters has helped to eliminate the radiation of unwanted harmonics.

Among the high-power installations set up in 1930 those at Prague and Warsaw are worthy of note. The Warsaw transmitter, which has been provided by the Marconi Company, is of the power amplifier type, and has an aerial carrier energy of about 120 k.w., with 80 per cent, modulation. Broadcast receivers are necessarily, becoming more selective, and some form of band selection is provided in most high-class equipment. During the past year considerable advances were made in increasing the speed of long-distance facsimile transmission and reception, and apparatus for this purpose is being installed for inter-communication between England and Canada and England and South Africa. One system which can transmit and reproduce with great fidelity bankers’ cheques, order form, and even finger prints, can be employed on radio circuits over which a dependable radio-telephone service can be maintained. A f picture-carrier current of 2,200 cycles is used, and tuning fork oscillators are employed at each end to generate a synchronising current identical in frequency with that of the other terminal.: A picture measuring 13cm. by 18cm. can be transmitted by this system in one and a-half minutes with a scansion of 40 lines per c.m. Shortly a picture-trans-mission service of this type will be operated over the Buenos Aires-Madrid radio link, and a further interesting development is a service between shorq stations and ships at sea by means of the short-wave ship-to-shore service, operated by the International Marine Radio Company. Interesting developments have taken place in marine communication equipments. The old spark transmitters are rapidly being replaced by C.W. and I.C.W. sets. At the present time the installation of spark sets of greater power than 300 watts is not allowed, and the ultimate intention is that even these shall be replaced by valve transmitters. This given rise to a demand for simple transmitters suitable for small craft. An equipment of this kind, produced by the international Marine Radio Company, gives telephone and telegraph service. Having an input power' of 150 watts, and bqing capable of operation on any wavelength between 150 and 800 metres, it provides an antenna power of 40 watts for C.W. and I.C.W. telegraphy and 25 watts for telephony. The receiver used in conjunction with this equipment covers a wave band from 40 to 20,000 metres. Its range for telegraphy is up to 10 miles, and half that distance for telephony. -

THE SMALL SET. A new radio receiver, demonstrated recently in New York, is expected to find favour in homes or apartments where space is limited. The set has seven tubes, so arranged around a magnetic cone that it is possible to contain everything, including the powerpack, in a cabinet of dimensions about equal to those of the average dynamic speaker. The set from the front gives 'the appearance of being a speaker only. The single dial tuning control on the right and a knob for regulating the volume at the extreme left, however, , reveal the presence of the receiver. Weight of the unit is so negligible that it may be moved easily from one room to another. It needs only an accessible 110-volt alternating current outlet, with some form of antenna and ground, to operate it in any new location. SOLDERING FLUX. The best flux for radio soldering connection is, of course, one that will not corrode, and resin is ideal ‘for this purpose when properly handled. To make a resin paste melt two parts of\ resin, add one part of melted vaseline or enough to obtain the consistency desired. The resin must be melted slowly, and care must be taken to prevent it from burning, as the paste will not function as a flux if this happens. A safe way to melt the resin is to use a sand bath, which diffuses the heat with less danger of scorching. A good soldering flux is made by dissolving a sufficient quantity of powdered resin in denatured alcohol to form a thick liquid, which, is applied with a small brush to the parts to oe soldered. This solution can also oe used as a binder to bold turns of wire in place on coils, as it dries quickly, and leaves a hard layer of resin, which will not be affected by ordinary heal or handling. To determine if a. commercial soldering paste is corrosive, take, a piece of copper wire that is slightly tarnished and smear some of the paste on it. Allow it to remain on the wire for a day or two, then rub it off. If the surface is bright, the paste is, corrosive, and should not be used in a radio set.