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The progress reviewed from a survey of the apparatus exhibited at the Berlin Radio Show.
As in former years, the television industry contributed richly to the Berlin Radio Exhibition. . It must, however, be noted that in Germany there seems to be little intention to push the sale of television sets at present. There is a disposition to wait and see whether the present type of transmission using ultra-short waves, is going to remain; also, whether the 180 line picture will be adhered to, for although this number of lines gives a satisfactorily sharp image, there is already a feeling in favour of a larger number of lines. Another fact restricting development in Germany is that at present only Berlin is provided with ultra-short wave transmissions, and these have a range only of about 50 km.
Fig. 1. - The Tekade receiver with mirror-screw tor 180 lines.
The following points emerge from this year's exhibit. The picture brightness has been increased considerably by the use of high-power high-vacuum cathode-ray tubes. The cathode-ray tube is now practically universal., but Tekade still keep to the mirror-screw (Fig. 1), which is designed for 180 lines.
 
Fig. 2. - The Telefunken cathode-ray television receiver. Fig. 3. - An interior view of the Telefunken equipment.
The Telefunken picture-and-sound receiver is shown in Figs. 2 and 3. The picture receiver is of the superheterodyne type, with a preliminary HF stage, a mixing stage acting also as oscillator, and a four-stage IF amplifier. By the use of highly damped intermediate circuits it is arranged that the whole frequency band which has to be transmitted, some one million cycles/sec in width, is uniformly reproduced, giving an improved sharpness of contrast. Naturally, this high damping would reduce the amplification were it not for the fact that special new valves of particularly steep slope (8-9 milliamps/volt) are used.
The sound receiver is a three-valve reflex set, and both receivers are worked off a common aerial with a coupling circuit arranged to prevent mutual interference The picture signals, after passing through the picture receiver, arrive at an electrical 'distributor' which separates, the image frequencies from the scanning frequencies and sends each to its proper circuit. Synchronisation is obtained by impulses from the transmitter.
A mains transformer is provided with two rectifiers - one providing the HT for the cathode-ray tube and the other the anode voltages for the picture and sound receivers, and for the 'distributor' and scanning circuits. Great care has been taken to ensure that the common mains unit does not lead to interaction between the various circuits.
Fig. 4.-The Fernseh Company's direct-scanning apparatus for 180 lines.
The Fernseh Company showed a sound-and-film transmitter and a light-beam scanner (Fig. 4). Both of these are provided with a fading-in arrangement so that spoken comments on the film may be introduced. In both transmitters the perforated discs rotate in a vacuum. In the case of the light-beam scanner the illumination is by a new type of high-power arc with a current consumption of 150 Amperes. The film transmitter will deal with standard films up to 1,500 metres, or (for test purposes) will use a continuous strip. The optical systems of both transmitters have been improved so as .to have a very high efficiency.
Portable Television Transmitter
The Fernseh Company also showed a television transmitting truck; this works on the well-known intermediate film system, but this year the film is dried immediately after the transmission and is ready for use as a negative for copying. The camera and photographic section can be kept out of action and the television transmitter used as an ordinary film-transmitter, so that a particular subject can be repeated as often as desired. The same firm again showed a large picture projecting receiver on the continuously working intermediate film principle, giving 3 ×4 metre pictures. In their home receiver (cathode-ray tube) the image measures 24 × 30 centimetres.
Fig. 5. - Von Ardenne with one of his high power cathode-ray tubes.
The Loewe Company showed a similar system to that of the previous year. One receiver only is used for sound and picture; otherwise the arrangement resembles that of Telefunken. Von Mihaly did not exhibit, but von Ardenne showed his high-power cathode-ray tube (Fig. 5). ' An important point in von Ardenne's apparatus is that he uses an aperiodic amplifier with an enormous frequency range. For picture reception he uses a superheterodyne, the intermediate frequency of which is rectified in the cathode-ray tube itself, the lower bend of the tube characteristic being employed. In this way interference due to a separate demodulator is eliminated. For sound reception an ultra-short wave audion receiver is employed instead of a superheterodyne.
Tekade showed a very economically priced kit set, containing all the parts of an ultra-short wave television receiver. It includes a new output transformer passing all the frequencies involved in 180-line transmissions. Although not actually exhibited, it is anticipated that in a few months time a very interesting invention - a 'light amplifier' will be developed. This is an entirely new idea, and will enable the light of dim television images to be so intensified that a cathode-ray tube image may be projected on to a large screen.
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