Radio mirror (Jan-Oct 1923)

RADIO DIGEST May 12, 1923 FIRST STEPS IN RADIO (Continued from page 11) At night this strata of ratified air is presumably lather clearly defined and acts as a reflector to reflect the waves back to earth as shown in Figure 4. This accounts for the greater night range of Radio sets. When the sun is shining the upper layers of the atmosphere are ionized or electrified and thus made partially conducting, but since this area of conducting medium is not as clearly defined as at night more or less absorption takes place. Local Condition Affects Reception The above are natural conditions existing about the earth, but we have in addition local conditions that affect the reception of Radio waves. As a rule the waves follow rather closely the surface of the earth, but when mountains are reached part of their energy is absorbed resulting in the valley beyond being in a sort of wave shadow that weakens the received signals materially. In a similar manner large conducting structures such as the metal framework of a building serve to cast shadows, figuratively speaking, that often makes reception difficult if not impossible from certain directions. The waves have no difficulty in passing through masses of matter provided they are good insulators, but when conducting masses are encountered a short circuiting effect takes place that absorbs the energy. The effect of this is to cut a sort of gap in the wave front, but the rest of the wave travels on and closes up the gap again but the total energy in the wave is reduced. In using a loop aerial the presence of conducting masses in the neighborhood causes distortion of the wave's front and thus gives erroneous directional effects when the loop is used as a compass. Aerial at Receiving Station So much for the emission and propagation of the waves. Let us consider how they affect the aerial at the receiving station. In a generator we have a fixed magnetic field through which wires on the armature are rapidly moved, resulting in a current being generated in them. A similar phenomena takes place at a receiving station for Radio waves with the exception that We have a stationary conductor, the aerial, across which the Radio waves with their magnetic field sweep, thus generating a current. At the same time the electrostatic component of the wave induces a current in the aerial to assist that induced by the magnetic field. Since the electrostatic stress reverses in direction with each wave with the magnetic field being likewise reversed, an alternating current is induced in the receiving aerial. By properly tuning the receiving aerial so that its period of oscillation is the same as the transmitting aerial each succeeding wave will add to the energy in the circuit with an increase of current value to act on the detecting device used. The two aerials are said to be then in resonance and maximum signal strength results. Waves Modulated "We have considered a simple wave without modulation for the sake of clearness but it is necessary that the waves be modulated or changed in order to transmit signals or speech. In Continuous "Wave Telegraphy this is done by simply starting and stopping the waves to form the telegraph code or to throw the transmitting aerial in and out of resonance with the receiver. The frequency of the waves at short wave lengths is too great to be audible, so it is necessary to produce beats in the receiver circuits that they may be audible but this will be covered later on. In Radio telephony the problem is more difficult. Upon the plain wave emitted at Radio frequency is impressed the audio wave or the variations of the currents from a microphone. The voice wave modulates or clips off the tops of the emitted waves as shown in the illustration, Figure 5. Here we see the voice wave forms a sort of envelope for the waves of higher frequency. However, we cannot hear the individual carrier waves because of their high frequency, but we can detect variations in the amplitude of the waves, which takes place at audible frequencies. In this manner the sound waves affecting the microphone in the transmitting station are carried by the Radio waves and impressed upon the receiving aerial to produce inleiiigible speech, (TO BE CONTINUED) Use water piping, and not gas piping, for grounding the Radio equipment. Reviews of Books 10c will bring you immediately our 32-page booklet containing complete diagrams and descriptions of Flewelling, Reinartz, Super-Regenerative and other circuits. Information about tubes, hints on construction of sets and other valuable and instructive data for everyone interested in Radio is included. Our complete line of standard equipment is also illustrated and described — an up-todate catalog of the newest in Radio at right prices. FREMONT RADIO SALES CO. 227-229 Fulton St. NEW YORK CITY How to Retail Radio. A new book telling of tested plans and methods and policies for the dealer in Radio. Financing, location, store equipment and arrangement. Price, $2.00. Vacuum Tube Receivers. By O. F. Heslar. A book that tells how to make a simple set. How to make the cabinet. It includes a 27 by 36-inch layout blue print. Price, 75 cents. The Armstrong Super-Regenerative Circuit. By George J. Eltz, Jr., E. E. This is a De Luxe edition of this famous circuit. Profusely illustrated and fully explained. Fifty-two pages. Price, $1.00. Iiefax Radio Handbook. A loose-leaf handbook. This book never grows old or out of date. All of the latest apparatus and hook-ups are added as time goes on. Anything that grows old is taken out and new leaves substituted. Price, $3.50. Home Radio — How to make It. By A. Hyatt Verrill. This book is particularly adapted for the amateur who desires to know how to make Radiophones. Twelve full page illustrations and diagrams. Price, 75 cents. Elements of Radiotelegraphy. By Elery W. Stone. The text was written for the guidance and instruction of Radio students in the communication service of the Navy. It is an instruction book for Radio schools. Price, $2.50. Radio for the Amateur. By A. H. Packer and R. R. Haugh. The underlying principles of Radio thoroughly explained in simple language and understandable illustrations. This book will teach you how to construct and operate a receiving set successfully. Price, $1.50. Electrical Year Book. By Frank H. Bernhard. An encyclopedia of current information about each branch of the electrical industry, with a dictionary of electrical terms. It includes a classified directory of electrical terms and related products and their manufacturers in the United States and Canada. Price, $10.00. The ABC Vacuum Tubes. By E. H. Lewis. Is a book for beginners who have no knowledge of either Radio or electricity and sets forth the elementary principles of theory and operation of the vacuum tube. No attempt has been made in this book to describe all the possible circuit arrangements, but those shown may serve as suggestions to experimenters who desire to evolve their own circuits. Price. $1.00. Radio Reception, By Harry J. Marx, Technical Editor Radio' Digest Illustrated, and Adrian "Van Muffling. A simple treatise on Radio reception. Beginning with the elementary principles of electricity it carries the reader on into the essentials of Radio telephony. The most successful methods of Radio reception are explained and special reference given to practical tuning. 230 pages, with 130 illustrations. Price, $2.00. The book department of the Radio Digest is prepared to send you any of the books on Radio published, whether listed in our Book Review or not. Let us know what book you want, send us your check and we will see that the book is mailed to yon. Postage stamps in payment for books not accepted. Send money order or check. Radio Book Department, Radio Digest, 123 W. Madison St., Chicago, 111. If the polarity of your B battery is reversed, do not expect to hear signals. /A^WE REPAIR WD-11, $3.50 and OTHER VACUUM TUBES Excepting VT-I and VT-II MAIL ORDERS Solicited and Promptly Attended To H & H RADIO GO. 516 Clinton Avenue NEWARK, N. J. We Will flail You One IF SYNTHETIC RADIO CRYSTAL COMPARE IT WITH WHAT YOU ARE NOW USING OURS IS BETTER MAIL US 30 CENTS NOT Return it at Our Expense JZOB EL STEIN LABORATORIES 322 9™ST. BR00KLYN.N.Y.S0UIH265O. Keep Dials from Scraping The scraping of dials on the panel of a Radio set can be corrected by placing a thin piece of felt on the back of the dials. They will then work smoothly without noise. For Silent Operation Shield the back of the panel with a thin sheet of metal, solder all connections tightly, make sure that the switch points and arms are not loose, use spaghetti with wires coming from„the tops of the vario coupler and insert a variable grid leak in the circuit. By this method it is often possible to get rid of most of the unpleasant noises. Connecting Batteries When connecting batteries to other Radio., units, trouble may be avoided by connecting the wires to the battery last, and then just touch the last wire before making permanent connection. There is always a possibility of having wrong connections. ANNOUNCEMENT The GREAT NORTHERN STEAMSHIP COMPANY (Incorporated) BOSTON, MASS. 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Organized by progressive business men who realize the exceptional opportunity offered now for inexpensive travel in Europe, the Company will cater to the thousands of intelligent persons who wish to visit the battlefields of France, the Shakespeare country, Scandinavia, the Land of the Midnight Sun, etc. A chance of a lifetime! So it would seem; but it is more than that. The company is building for a permanent business, setting a new standard of high-class ocean travel on a one-class basis. That this can be done at a fair margin of profit has already been proved and is further outlined in our prospectus. You'll find it extremely interesting. WE WILL ALSO SHOW YOU HOW YOU MAY BECOME A PART-OWNER IN THE MOST TALKED OF ENTERPRISE IN YEARS. Cut out and mail us with your name and address. A. Wikstrom Information Dep't Edmunds Bldg., Suite 54 Boston, Mass. I am interested in securing full information regarding a trip to: (Mark with a cross) One Way Round Trip England France Germany Sweden Norway Denmark Baltic Provinces Finland Russia Name Street or R.f.d City or Town State A. Wikstrom -v Information Dep't Edmunds Bldg., Suite 54 Boston, Mass. I am interested in becoming partowner in the Great Northern Steamship Company. Please send me prospectus and full particulars. Name Street or R.f.d City or Town State IU911