Radio mirror (Jan-Oct 1923)

12 RADIO DIGEST ILLUSTRATED Coil of Wire Tunes Radio Frequency Radio Frequency Helps Bring in New Stations A stage of Radio frequency will bring in new stations that cannot be heard with just a detector and audio amplification. The tuned type of transformer is easy to WORKSHOP KINKS? EARN A DOLLAR— THERE are many little kinks worked out at home that would aid your fellow Radio worker if he only knew about them. There are new hook-ups, new ways of making parts and various unique ways of operating sets that are discovered every day. RADIO DIGEST is very much interested in securing such material. Send them in with full details, including stamped envelope so rejected copy may be returned. The work must be entirelv original, not copied. RADIO KINKS DEPARTMENT, RADIO DIGEST, 123 West Madison St., Chicago, 111. construct in the home workshop and gives just as good results when accurately constructed as the core transformer. It is not practical to use more than two stages LEAP. ■#■ VAR.COND. LEAD. COIU6FW\RE. L-A/WSAAMA— ' of tuned Radio frequency amplification. The ordinary hard amplifier tubes should be used just like the ones used for audio amplification. TWO CIRCUITS USING TUNED COIL PLATE OF DETECTOR TUBE. *■ TO PHONE * TO GRID LEAK * DET. TUBE. TO PHONE. NEG.FILAMENTOF DETECTOR.. 6 V. gg&V.I Z&XsdL A 23 or 43 -plate variable condenser is connected in parallel with a coil of wire wound on a cardboard or fiber tube. This coil consists of about 38 to 40 turns of No. 22 to No. 24 wire on a tube about 3a/£ inches in diameter. A diagram is given for connecting the transformer coil with the condenser and also for one and two stages of Radio fre quency as connected in the circuit of the Radio set. The transformer is simply connected across the circuit of the tuning coil. This type of transformer is critical in adjustment which is a great advantage as it eliminates interference. It is easy to construct and gives excellent results. — Charles L. Smith, Jackson, Miss. A. B. C. LESSONS (Continued from page 11) Some say that certain rays from the sun render certain sections of the air conductive and hence enable it to absorb some of the energy of the Radio waves and thus make them less effective. Furthermore, it is also known that the transmitting range, that is, the distance messages can be sent effectively, also varies from day to day due to the various electrical conditions of the atmosphere. Another annoyance is that on warm days Radio transmission is often interfered with. This is explained by some as being due to the greater quantities of water vapor present in the air. This vapor is frequently heavily charged with static electricity, which not only attracts and absorbs considerable amounts of energy from the ether, but also seems to collect and accumulate on receiving aerials and produce unpleasant sounds in the telephone receivers. It is said that this is the reason that greater ranges can be covered with the same amount of power during the winter than during the summer months. A very peculiar condition that exists in many mountainous regions is that Radio waves are reflected from the sides of a high mountain or hill and in this maner cause what is known as an "electrical shadow" on the opposite side. This is similar to the sun shining on one side of a billboard, being reflected, *and causing a shadow on the other side. Such conditions often cause the various freak messages that are heard occasionally, for the direct and reflected waves combine and produce the most peculiar results. An important point to bear in mind is that it isn't always static that is the cause of noise or trouble in a receiving set. There may be a broken or loose connection somewhere, or the antenna may be under the inductive influence of some nearby telephone or power line. The Receiving" Station The Radio receiving station, we were told, corresponds to the cork that was floating on the water in which the disturbance or wave motion was set up. And as the cork responded in every respect to the nature of the waves that passed it, so the Radio receiving station will be influenced and caused to respond to the Radio waves that pass it. In order that the receiving station will be influenced by the Radio waves as they pass through space, it must be provided with some form of antenna or aerial to intercept the waves and absorb part of their energy. This receiving antenna may be in the form either of one or more parallel wires stretched out into space, or a spiral or coil of wire commonly known as a loop antenna. As the advancing Radio waves come upon the receiving antenna, they set up in it by the process of electromagnetic induction electrical oscillations of the same frequency. Connected to the receiving antenna is some form of "tuning apparatus" by means of which the antenna can be tuned or adjusted so that it will respond only to a particular wave length and be non-susceptible to waves of other lengths that may be passing through space at the same time. Receiving' Stations Unlimited in Number It is evident that the number of receiving stations existing within the vicinity of a transmitting or broadcasting station will have but little effect upon the strength of the signals received in any one station, because as the waves advance they will have but very little of their energy intercepted by the receiving antennas. The electrical oscillations as set up in the receiving antenna, however, are at a very high frequency and far too rapid to affect the human ear and produce the sensation of sound. The receiving station must, therefore, contain additional apparatus for reducing these high frequencies to lower frequencies at which they can be detected as sounds. Furthermore, this reduction in frequency must be accomplished without in any way altering or distorting the incoming oscillations, for otherwise the sounds heard in the receivers will not correspond to those originally sent out at the transmitting station and the received signals would have no meaning. Also, the oscillations are still of an electrical nature and must finally be converted into sounds so that they can be detected by the human ear. This is accomplished by means of telephone receivers, in which we have a sensitive electromagnet that is affected by the electrical oscillations and that in turn moves a diaphragm. This diaphragm by its rapid back and forth motion produces the sounds. Figure 16 Explanation In Figure 16 we have illustrated diagramatically the various parts comprising a complete Radio communication system. G is the electrical generating device in which high frequency electrical oscillations are generated. These high frequency oscillations excite the antenna, A-l, and cause the electromagnetic waves to be radiated into space. As these waves move onward they are intercepted by the antenna A-2 of a receiving station. Electrical oscillations of corresponding nature and frequency are set up in the receiving antenna and these in turn affect the receiving apparatus, R. Here the frequencies are reduced and finally sent through the telephone receivers P H, where the electrical oscillations are changed to sounds that can be detected by the human ear. Although all these processes and transformations may seem rather simple to us now, we must not forget that they represent the results of a great deal of time and effort spent in study and research work by some of the world's keenest investigators. The human ear can detect sounds only up to certain frequencies, above which sounds become inaudible. Since the frequencies used for Radio communication are far beyond those which the human ear can be influenced by, they are generally spoken of as Radio frequencies, while frequencies capable of affecting the human ear are known as audio frequencies, the word audio coming from the word audible, capable of being heard. The dividing line is drawn at 10,000. Frequencies below 10,000 per second are known as audiofrequencies, while frequencies above this value are known as Radio frequencies. Chapter Five In Chapter Five will be taken up the complete details of construction and operation of a crystal detector receiving set. Since a crystal detector set is readily constructed at little cost, and since it gives excellent results for listening in to nearby stations, no one who wants to enjoy the thrills of Radio can afford to miss Chapter Five, which will appear in next week's issue. Radio Study Methods To obtain the best results in Radio, the amateur, to increase his knowledge, should study in the following order: Construction, arrangement operation, function, care and principles of operation. Helps for Honeycomb Coil Users Persons using honeycomb coils wish to try out some other kind of coils as an experiment, such as a regenerative set or a single circuit tuner. It is usually necessary to make a lot of bothersome changes in order to make the experiment. If three Remler stationary plugs are secured and plugged in the regular mounting wires may be attached to the external binding posts on these plugs so that any kind of coils may be used. — Hollis Baird, Canada. The modern rural school is beginning to take up Radio instruction from the more populous centers. In Hawaii a powerful transmitting plant installed by the public department at Honolulu sends out educational subjects to the schools in the rural districts. Honeycomb Coils Used In Reinartz Circuit The diagram is of the Reinartz circuit using three duolateral coils and mounting. I have been using this hook-up for some time and have been getting far superior results than with the regular Reinartz circuit. Some features to this hook-up is the fine selectivity in tuning out undesirable stations which are operating on practically the same wave length. I have picked up stations on the Pacific Coast in the early part of the evenings while the large stations are broadcasting and have had no interference from them. No extra apparatus are required to change over to this hook-up. The diagram is shown with a variable condenser of .0005 7 ANTENNA GROUND -6 -Hi w d» mfd. capacity in the tickler coil. This condenser can be replaced by a fixed condenser of the same capacity. — C. C. Dieffenbacher, Memphis, Tenn. Clamping Fixed Condenser Those who use the rolled type paper condensers, such as for the grid and phone condensers, may find that considerable noise in their sets will result when the paper comes loose from the tinfoil. This can be easily remedied by placing the con STRING CONDENSER* denser between two pieces of wood and clamping the whole in a vise, then tying the ends of the wood securely with heavy silk thread. This will keep the paper and tinfoil pressed tightly and prevent the noise from this source. — William A. Nash, Biddeford, Maine. Phantom Tuner W-75 will brine one of these marvelously sensitive instruments to your address, prepaid. No aerial, ground, loop or radio frequency used. All parts highest quulity. Cutler Hammer. Remler, Dubelier. etc.. mounted on eenuine bakelite panel. Complete instructions furnished for wirine . No solderine necessary . Have music on strip of lamp cord one hour after set arrives. Our Phantom gets over distance and is practical using detector only . Wind lamp cord in auto top and tune in music while driving. We've done it often. Send stamp for booklet and learn the Phantom story VESCO RADIO SHOP. Box D-704, Vacaville, Calif. FRESHMAN VARIABLE GRID LEAK With Micon Condenser Without Condenser $1.00 75c Clarifies Signals, Lowers Filament Current, Increases Battery Life, Eliminates Hissing. Unbroken range — zero to 5 Megohms; all intermediate points.. Fixed capacity, .00025 M. F. At your dealer's — otherwise send purchase price and you will be supplied without further charge. Manufactured by CHAS. FRESHMAN CO., Inc. 97 Beekman Street, New York City tffctQtW BETTER LOUD SPEAKER $0 I? ~"° TRUE TARINFT TYPF O ,85 Not just a common horn built into a cabinet. Beautiful — Compact—THE TONE OE FINE CABINET PHONOGRAPHS. Make your two-step set a HOME ENTERTAINER. All SPI ROLAS are of the best construction, with fine, rubbed finishes and are absolutely guaranteed. SPIROLA DUPLEX— uses any headset. Satin black (DB) finish $3.85. Oak (DO) or mahogany (DM) finish $4.85. SPIROLA SIMPLEX— uses Baldwin or other unit Black (SB), oak (SO), mahogany (SM) finish, same prices as DUPLEX. SPIROLA CONCERT— complete trith built-in unit and cord. Oak (CO) or mahogany (CM) finish $12.50. At dealers or postpaid (C 0. D, if preferred) L. H. DONNELL MFG. CO., DEPT. D, BOX 70, ANN ARBOR. MICH. ..