Radio Broadcast (May-Oct 1922)

RADIO BROADCAST 99 means of radio communication with the outside world. Now we learn that a radio service between Stockholm and Petrograd was inaugurated recently. A New Russian Station A Central News message states that a powerful radio station, capable of direct communication with Germany, England, Denmark, and Norway is nearing completion at Dietskoye Selo in Russia. It has been planned entirely by Russian engineers and erected by Russian labor. Cable and Radio AN interesting and convincing comparison /\ as to the relative cost of operating a / \ cable and a radio system may be gathered from the figures quoted by an Australian radio company, which plans to give a radio telegraph service between Australia and England, at one-third less than the cost of cable communication . The cost of establishing this service would be roughly $5,000,000, of which the company already has about half that amount. Radio Calling Apparatus FROM F ranee comes the news that L. Chauveau has developed a simple and reliable system whereby a radio operator may call up a certain person or station, in order to compete with ordinary wire telephony and telegraphy. This French inventor claims to have solved this problem and gives a description of his automatic radio calling apparatus in a recent issue of Radioelectricite. It consists of a combination of twenty magnetic relays — ten corresponding to "dot" and ten to "dash" calls, as well as a time relay. The apparatus can be set for any combination up to five letters or numerals, and if the call arrives in proper sequence and at proper time intervals, the last relay will close a signalling circuit, notifying the attendant of the receiving station. To ensure the essential accuracy of sequence and time, the sending station emits the call with a mechanical caller. The Airplane and the Radio Beacon WITH the rapid strides now being made in commercial aviation throughout Europe, the matter of radio beacons, as radio compass installations are called when employed to guide aircraft. is an important one. It seems now that in the very near future there will be automatic radio telegraph transmitters located at regular intervals along air routes for the purpose of transmitting characteristic signals whereby any aircraft pilot can secure his bearings by checking up on two or more radio beacons. For the present, aircraft pilots depend on the usual radio stations, whom they ask for information concerning their bearings. In the future, the airships and airplanes will probably carry their own radio compass installations and will have to figure out their own bearings. The British Mullard Tubes IN THE United States we think of Radiotrons when we turn to vacuum tubes, not that there are no other tubes to be had, but because the Radiotions are in such general use. In England, on the other hand, the amateurs think of Mullard radio valves. The British amateur makes use of the Mullard tubes made for receiving purposes. These tubes, or valves, as they are called, are made in a variety of types. The most common type is the type R, which has an overall length, including pin contact members, of 4I inches and a bulb diameter of 2j inches. It works best on a filament voltage of 4, and 60 to 80 volts between the plate and the filament. In the K type, which is somewhat more compact, about volts is required for the filament, and 20 to 30 volts for the plate circuit. This particular type is suitable for use in radio frequency amplifiers. The D type is a slightly soft tube designed for use in detecting or rectifying signals prior to audio-frequency amplification. It operates best at about 5 volts filament current, and 20 to 30 volts for the plate circuit. The electrodes of the Mullard tubes are made from sheet nickel, and molybdenum and tungsten wire. The Mullard valves or tubes for transmitting purposes have bulbs made with silica, which not only reduces the danger of breakage but also permits of bringing the container nearer to the filament and grid so as to reduce the size of the tube. The England-Egypt Radio Link COMMUNICATION has been established between the Leafield (Oxfordshire, England) and the Abu Zabal (Cairo, Egypt) stations, but no commercial facilities are yet available, according to latest advices. In reply to a question in the