The Radio Amateur's Hand Book / A Complete, Authentic and Informative Work on Wireless Telegraphy and Telephony

The Tuning Coil.--You will have to make this tuning coil, which you can do at a cost of less than $1.00, as the cheapest tuning coil you can buy costs at least $3.00, and we need the rest of our $5.00 to invest in the earphone. Get a cardboard tube, such as is used for mailing purposes, 2 inches in diameter and 3 inches long, see A in Fig. 97. Now wind on 250 turns of No. 40 Brown and Sharpe gauge plain enameled magnet wire. You can use No. 40 double cotton covered magnet wire, in which case you will have to shellac the tube and the wire after you get it on.

As you wind on the wire take off a tap at every 15th turn, that is, scrape the wire and solder on a piece about 7 inches long, as shown in Fig. 99; and do this until you have 6 taps taken off. Instead of leaving the wires outside of the tube bring them to the inside of it and then out through one of the open ends. Now buy a round wood-base switch with 7 contact points on it as shown at B in Fig. 97. This will cost you 25 or 50 cents.

The Headphone.--An ordinary Bell telephone receiver is of small use for wireless work as it is wound to too low a resistance and the diaphragm is much too thick. If you happen to have a Bell phone you can rewind it with No. 40 single covered silk magnet wire, or enameled wire of the same size, when its sensitivity will be very greatly improved. Then you must get a thin diaphragm and this should not be enameled, as this tends to dampen the vibrations of it. You can get a diaphragm of the right kind for 5 cents.

The better way, though, is to buy an earphone made especially for wireless work. You can get one wound to 1000 ohms resistance for $1.75 and this price includes a cord. [Footnote: This is Mesco, No. 470 wireless phone. Sold by the Manhattan Electrical Supply Co., Park Place, N.Y.C.] For $1.00 extra you can get a head-band for it, and then your phone will look like the one pictured in Fig. 98.

How to Mount the Parts.--Now mount the coil on a wood base, 1/2 or 1 inch thick, 3-1/2 inches wide and 5-1/2 inches long, and then connect one end of the coil to one of the end points on the switch, and connect each succeeding tap to one of the switch points, as shown schematically in Fig. 99 and diagrammatically in Fig. 100. This done, screw the switch down to the base. Finally screw the detector to the base and screw two binding posts in front of the coil. These are for the earphone.

The Condenser.--You do not have to connect a condenser across the earphone but if you do you will improve the receiving qualities of the receptor.

How to Connect Up the Receptor.--Now connect up all the parts as shown in Figs. 99 and 100, then connect the leading-in wire of the aerial with the lever of the switch; and connect the free end of the tuning coil with the ground. If you have no aerial wire try hooking it up to a rain pipe that is not grounded or the steel frame of an umbrella. For a ground you can use a water pipe, an iron pipe driven into the ground, or a hydrant. Put on your headphone, adjust the detector and move the lever over the switch contacts until it is in adjustment and then, if all your connections are properly made, you should be able to pick up messages.

APPENDIX

USEFUL INFORMATION

ABBREVIATIONS OF UNITS

PREFIXES USED WITH METRIC SYSTEM UNITS

SYMBOLS USED FOR VARIOUS QUANTITIES

TABLE OF ENAMELED WIRE

TABLE OF FREQUENCY AND WAVE LENGTHS

PRONUNCIATION OF GREEK LETTERS

Many of the physical quantities use Greek letters for symbols. The following is the Greek alphabet with the way the letters are pronounced:

TABLE OF SPARKING DISTANCES

In Air for Various Voltages between Needle Points

FEET PER POUND OF INSULATED MAGNET WIRE

INTERNATIONAL MORSE CODE AND CONVENTIONAL SIGNALS

1. A dash is equal to three dots.
2. The space between parts of the same letter is equal to one dot.
3. The space between two letters is equal to three dots.
4. The space between two words is equal to five dots.

[Note: period denotes Morse dot, hyphen denotes Morse dash]

INTERNATIONAL RADIOTELEGRAPHIC CONVENTION

LIST OF ABBREVIATIONS TO BE USED IN RADIO COMMUNICATION

[Footnote: Public correspondence is any radio work, official or private, handled on commercial wave lengths.]

When an abbreviation is followed by a mark of interrogation, it refers to the question indicated for that abbreviation.

Useful Information

Symbols Used For Apparatus

alternator
ammeter
aerial
arc
battery
buzzer
condenser
variable condenser
connection of wires
no connection
coupled coils
variable coupling
detector
gap, plain
gap, quenched
ground
hot wire ammeter
inductor
variable inductor
key
resistor
variable resistor
switch s.p.s.t.
" s.p.d.t.
" d.p.s.t.
" d.p.d.t.
" reversing
phone receiver
" transmitter
thermoelement
transformer
vacuum tube
voltmeter
choke coil

DEFINITIONS OF ELECTRIC AND MAGNETIC UNITS

The ohm is the resistance of a thread of mercury at the temperature of melting ice, 14.4521 grams in mass, of uniform cross-section and a length of 106.300 centimeters.

The ampere is the current which when passed through a solution of nitrate of silver in water according to certain specifications, deposits silver at the rate of 0.00111800 of a gram per second.

The volt is the electromotive force which produces a current of 1 ampere when steadily applied to a conductor the resistance of which is 1 ohm.

The coulomb is the quantity of electricity transferred by a current of 1 ampere in 1 second.

The ampere-hour is the quantity of electricity transferred by a current of 1 ampere in 1 hour and is, therefore, equal to 3600 coulombs.

The farad is the capacitance of a condenser in which a potential difference of 1 volt causes it to have a charge of 1 coulomb of electricity.

The henry is the inductance in a circuit in which the electromotive force induced is 1 volt when the inducing current varies at the rate of 1 ampere per second.

The watt is the power spent by a current of 1 ampere in a resistance of 1 ohm.

The joule is the energy spent in I second by a flow of 1 ampere in 1 ohm.

The horse-power is used in rating steam machinery. It is equal to 746 watts.

The kilowatt is 1,000 watts.

The units of capacitance actually used in wireless work are the microfarad, which is the millionth part of a farad, because the farad is too large a unit; and the C. G. S. electrostatic unit of capacitance, which is often called the centimeter of capacitance, which is about equal to 1.11 microfarads.

The units of inductance commonly used in radio work are the millihenry, which is the thousandth part of a henry; and the centimeter of inductance, which is one one-thousandth part of a microhenry.

Note.--For further information about electric and magnetic units get the Bureau of Standards Circular No. 60, called Electric Units and Standards, the price of which is 15 cents; also get Scientific Paper No. 292, called International System of Electric and Magnetic Units, price 10 cents. These and other informative papers can be had from the Superintendent of Documents, Government Printing Office, Washington, D. C.

WIRELESS BOOKS

The Admiralty Manual of Wireless Telegraphy. 1920. Published by His Majesty's Stationery Office, London.

Ralph E. Batcher.--Prepared Radio Measurements. 1921. Wireless Press, Inc., New York City.

Elmer E. Bucher.--Practical Wireless Telegraphy. 1918. Wireless Press, Inc., New York City.

Elmer E. Bucher.--Vacuum Tubes in Wireless Communication. 1919. Wireless Press, Inc., New York City.

Elmer E. Bucher.--The Wireless Experimenter's Manual. 1920. Wireless Press, Inc., New York City.

1. Frederick Collins.--Wireless Telegraphy, Its History, Theory, and Practice. 1905. McGraw Pub. Co., New York City.
2. H. Dellinger.--Principles Underlying Radio Communication.
3. Signal Corps, U. S. Army, Washington, D. C.
4. M. Dorsett.--Wireless Telegraphy and Telephony. 1920. Wireless Press, Ltd., London.
5. A. Fleming.--Principles of Electric Wave Telegraphy. 1919. Longmans, Green and Co., London.

Charles B. Hayward.--How to Become a Wireless Operator. 1918. American Technical Society, Chicago, Ill.

G. D. Robinson.--Manual of Radio Telegraphy and Telephony. 1920. United States Naval Institute, Annapolis, Md.

Rupert Stanley.--Textbook of Wireless Telegraphy. 1919. Longmans, Green and Co., London.

E. W. Stone.--Elements of Radio Telegraphy. 1919. D, Van Nostrand Co., New York City.

L. B. Turner.--Wireless Telegraphy and Telephony. 1921. Cambridge University Press. Cambridge, England.

Send to the Superintendent of Documents, Government Printing Office, Washington, D. C., for a copy of Price List No. 64 which lists the Government's books and pamphlets on wireless. It will be sent to you free of charge.

The Government publishes; (1) A List of Commercial Government and Special Wireless Stations, every year, price 15 cents; (2) A List of Amateur Wireless Stations, yearly, price 15 cents; (3) A Wireless Service Bulletin is published monthly, price 5 cents a copy, or 25 cents yearly; and (4) Wireless Communication Laws of the United States, the International Wireless Telegraphic Convention and Regulations Governing Wireless Operators and the Use of Wireless on Ships and Land Stations, price 15 cents a copy. Orders for the above publications should be addressed to the Superintendent of Documents, Government Printing Office, Washington, D. C.

Manufacturers and Dealers in Wireless Apparatus and Supplies:

Adams-Morgan Co., Upper Montclair, N. J.

American Hard Rubber Co., 11 Mercer Street, New York City.

American Radio and Research Corporation, Medford Hillside, Mass.

Brach (L. S.) Mfg. Co., 127 Sussex Ave., Newark, N. J.

Brandes (C.) Inc., 237 Lafayette St., New York City.

Bunnell (J. H.) Company, Park Place, New York City.

Burgess Battery Company, Harris Trust Co. Bldg., Chicago, Ill.

Clapp-Eastman Co., 120 Main St., Cambridge, Mass.

Connecticut Telephone and Telegraph Co., Meriden, Conn.

Continental Fiber Co., Newark, Del.

Coto-Coil Co., Providence, R. I.

Crosley Mfg. Co., Cincinnati, Ohio.

Doolittle (F. M.), 817 Chapel St., New Haven, Conn.

Edelman (Philip E.), 9 Cortlandt St., New York City.

Edison Storage Battery Co., Orange, N. J.

Electric Specialty Co., Stamford, Conn.

Electrose Mfg. Co., 60 Washington St., Brooklyn, N. Y.

General Electric Co., Schenectady, N. Y.

Grebe (A. H.) and Co., Inc., Richmond Hill, N. Y. C.

International Brass and Electric Co., 176 Beekman St., New York City.

International Insulating Co., 25 West 45th St., New York City.

King Amplitone Co., 82 Church St., New York City.

Kennedy (Colin B.) Co., Rialto Bldg., San Francisco, Cal.

Magnavox Co., Oakland, Cal.

Manhattan Electrical Supply Co., Park Place, N. Y.

Marshall-Gerken Co., Toledo, Ohio.

Michigan Paper Tube and Can Co., 2536 Grand River Ave., Detroit, Mich.

Murdock (Wm. J.) Co., Chelsea, Mass.

National Carbon Co., Inc., Long Island City, N. Y.

Pittsburgh Radio and Appliance Co., 112 Diamond St., Pittsburgh, Pa,

Radio Corporation of America, 233 Broadway, New York City.

Riley-Klotz Mfg. Co., 17-19 Mulberry St., Newark, N. J.

Radio Specialty Co., 96 Park Place, New York City.

Roller-Smith Co., 15 Barclay St., New York City.

Tuska (C. D.) Co., Hartford, Conn.

Western Electric Co., Chicago, Ill.

Westinghouse Electric Co., Pittsburgh, Pa.

Weston Electrical Instrument Co., 173 Weston Ave., Newark, N. J.

Westfield Machine Co., Westfield, Mass.

ABBREVIATIONS OF COMMON TERMS

GLOSSARY

A BATTERY.--See Battery A.

ABBREVIATIONS, CODE.--Abbreviations of questions and answers used in wireless communication. The abbreviation of a question is usually in three letters of which the first is Q. Thus Q R B is the code abbreviation of "what is your distance?" and the answer "My distance is..." See Page 306 [Appendix: List of Abbreviations].

ABBREVIATIONS, UNITS.--Abbreviations of various units used in wireless electricity. These abbreviations are usually lower case letters of the Roman alphabet, but occasionally Greek letters are used and other signs. Thus amperes is abbreviated amp., micro, which means one millionth, [Greek: mu], etc. See Page 301 [Appendix: Useful Abbreviations].

ABBREVIATIONS OF WORDS AND TERMS.--Letters used instead of words and terms for shortening them up where there is a constant repetition of them, as A.C. for alternating current; C.W. for continuous waves; V.T. for vacuum tube, etc. See Page 312 [Appendix: Abbreviations of Common Terms].

AERIAL.--Also called antenna. An aerial wire. One or more wires suspended in the air and insulated from its supports. It is the aerial that sends out the waves and receives them.

AERIAL, AMATEUR.--An aerial suitable for sending out 200 meter wave lengths. Such an aerial wire system must not exceed 120 feet in length from the ground up to the aerial switch and from this through the leading-in wire to the end of the aerial.

AERIAL AMMETER.--See Ammeter, Hot Wire.

AERIAL, BED-SPRINGS.--Where an outdoor aerial is not practicable bed-springs are often made to serve the purpose.

AERIAL CAPACITY.--See Capacity, Aerial.

AERIAL COUNTERPOISE.--Where it is not possible to get a good ground an aerial counterpoise or earth capacity can be used to advantage. The counterpoise is made like the aerial and is supported directly under it close to the ground but insulated from it.

AERIAL, DIRECTIONAL.--A flat-top or other aerial that will transmit and receive over greater distances to and from one direction than to and from another.

AERIAL, GROUND.--Signals can be received on a single long wire when it is placed on or buried in the earth or immersed in water. It is also called a ground antenna and an underground aerial.

AERIAL, LOOP.--Also called a coil aerial, coil antenna, loop aerial, loop antenna and when used for the purpose a direction finder. A coil of wire wound on a vertical frame.

AERIAL RESISTANCE.--See Resistance, Aerial.

AERIAL SWITCH.--See Switch Aerial.

AERIAL WIRE.--(1) A wire or wires that form the aerial. (2) Wire that is used for aerials; this is usually copper or copper alloy.

AERIAL WIRE SYSTEM.--An aerial and ground wire and that part of the inductance coil which connects them. The open oscillation circuit of a sending or a receiving station.

AIR CORE TRANSFORMER.--See Transformer, Air Core.

AMATEUR AERIAL OR ANTENNA.--See Aerial, Amateur.

ALTERNATOR.--An electric machine that generates alternating current.

ALPHABET, INTERNATIONAL CODE.--A modified Morse alphabet of dots and dashes originally used in Continental Europe and, hence, called the Continental Code. It is now used for all general public service wireless communication all over the world and, hence, it is called the International Code. See page 305 [Appendix: International Morse Code].

ALTERNATING CURRENT (A.C.)--See Current.

ALTERNATING CURRENT TRANSFORMER.--See Transformer.

AMATEUR GROUND.--See Ground, Amateur.

AMMETER.--An instrument used for measuring the current strength, in terms of amperes, that flows in a circuit. Ammeters used for measuring direct and alternating currents make use of the magnetic effects of the currents. High frequency currents make use of the heating effects of the currents.

AMMETER, HOT-WIRE.--High frequency currents are usually measured by means of an instrument which depends on heating a wire or metal strip by the oscillations. Such an instrument is often called a thermal ammeter, radio ammeter and aerial ammeter.

AMMETER, AERIAL.--See Ammeter, Hot Wire.

AMMETER, RADIO.--See Ammeter, Hot Wire.

AMPERE.--The current which when passed through a solution of nitrate of silver in water according to certain specifications, deposits silver at the rate of 0.00111800 of a gram per second.

AMPERE-HOUR.--The quantity of electricity transferred by a current of 1 ampere in 1 hour and is, therefore, equal to 3600 coulombs.

AMPERE-TURNS.--When a coil is wound up with a number of turns of wire and a current is made to flow through it, it behaves like a magnet. B The strength of the magnetic field inside of the coil depends on (1) the strength of the current and (2) the number of turns of wire on the coil. Thus a feeble current flowing through a large number of turns will produce as strong a magnetic field as a strong current flowing through a few turns of wire. This product of the current in amperes times the number of turns of wire on the coil is called the ampere-turns.

AMPLIFICATION, AUDIO FREQUENCY.--A current of audio frequency that is amplified by an amplifier tube or other means.

AMPLIFICATION, CASCADE.--See Cascade Amplification.

AMPLIFICATION, RADIO FREQUENCY.--A current of radio frequency that is amplified by an amplifier tube or other means before it reaches the detector.

AMPLIFICATION, REGENERATIVE.--A scheme that uses a third circuit to feed back part of the oscillations through a vacuum tube and which increases its sensitiveness when used as a detector and multiplies its action as an amplifier and an oscillator.

AMPLIFIER, AUDIO FREQUENCY.--A vacuum tube or other device that amplifies the signals after passing through the detector.

AMPLIFIER, MAGNETIC.--A device used for controlling radio frequency currents either by means of a telegraph key or a microphone transmitter. The controlling current flows through a separate circuit from that of the radio current and a fraction of an ampere will control several amperes in the aerial wire.

AMPLIFIERS, MULTI-STAGE.--A receiving set using two or more amplifiers. Also called cascade amplification.

AMPLIFIER, VACUUM TUBE.--A vacuum tube that is used either to amplify the radio frequency currents or the audio frequency currents.

AMPLITUDE OF WAVE.--The greatest distance that a point moves from its position of rest.

AMPLIFYING TRANSFORMER, AUDIO.--See Transformer, Audio Amplifying.

AMPLIFYING MODULATOR VACUUM TUBE.--See Vacuum Tube, Amplifying Modulator.

AMPLIFYING TRANSFORMER RADIO.--See Transformer, Radio Amplifying.

ANTENNA, AMATEUR.--See Aerial, Amateur.

ANTENNA SWITCH.--See Switch, Aerial.

APPARATUS SYMBOLS.--See Symbols, Apparatus.

ARMSTRONG CIRCUIT.--See Circuit, Armstrong.

ATMOSPHERICS.--Same as Static, which see.

ATTENUATION.--In Sending wireless telegraph and telephone messages the amplitude of the electric waves is damped out as the distance increases. This is called attenuation and it increases as the frequency is increased. This is the reason why short wave lengths will not carry as far as long wave lengths.

AUDIO FREQUENCY AMPLIFIER.--See Amplifier, Audio Frequency.

AUDIO FREQUENCY AMPLIFICATION.--See Amplification, Audio Frequency.

AUDIBILITY METER.--See Meter, Audibility.

AUDIO FREQUENCY.--See Frequency, Audio.

AUDIO FREQUENCY CURRENT.--See Current, Audio Frequency.

AUDION.--An early trade name given to the vacuum tube detector.

AUTODYNE RECEPTOR.--See Receptor, Autodyne.

AUTO TRANSFORMER.--See Transformer, Auto.

BAKELITE.--A manufactured insulating compound.

B BATTERY.--See Battery B.

BAND, WAVE LENGTH.--See Wave Length Band.

BASKET WOUND COILS.--See Coils, Inductance.

BATTERY, A.--The 6-volt storage battery used to heat the filament of a vacuum tube, detector or amplifier.

BATTERY, B.--The 22-1/2-volt dry cell battery used to energize the plate of a vacuum tube detector or amplifier.

BATTERY, BOOSTER.--This is the battery that is connected in series with the crystal detector.

BATTERY, C.--A small dry cell battery sometimes used to give the grid of a vacuum tube detector a bias potential.

BATTERY, EDISON STORAGE.--A storage battery in which the elements are made of nickel and iron and immersed in an alkaline electrolyte.

BATTERY, LEAD STORAGE.--A storage battery in which the elements are made of lead and immersed in an acid electrolyte.

BATTERY POLES.--See Poles, Battery.

BATTERY, PRIMARY.--A battery that generates current by chemical action.

BATTERY, STORAGE.--A battery that develops a current after it has been charged.

BEAT RECEPTION.--See Heterodyne Reception.

BED SPRINGS AERIAL.--See Aerial, Bed Springs.

BLUB BLUB.--Over modulation in wireless telephony.

BROAD WAVE.--See Wave, Broad.

BRUSH DISCHARGE.--See Discharge.

BUZZER MODULATION.--See Modulation, Buzzer.

BLUE GLOW DISCHARGE.--See Discharge.

BOOSTER BATTERY.--See Battery, Booster.

BROADCASTING.--Sending out intelligence and music from a central station for the benefit of all who live within range of it and who have receiving sets.

CAPACITANCE.--Also called by the older name of capacity. The capacity of a condenser, inductance coil or other device capable of retaining a charge of electricity. Capacitance is measured in terms of the microfarad.

CAPACITIVE COUPLING.--See Coupling, Capacitive.

CAPACITY.--Any object that will retain a charge of electricity; hence an aerial wire, a condenser or a metal plate is sometimes called a capacity.

CAPACITY, AERIAL.--The amount to which an aerial wire system can be charged. The capacitance of a small amateur aerial is from 0.0002 to 0.0005 microfarad.

CAPACITY, DISTRIBUTED.--A coil of wire not only has inductance, but also a certain small capacitance. Coils wound with their turns parallel and having a number of layers have a bunched capacitance which produces untoward effects in oscillation circuits. In honeycomb and other stagger wound coils the capacitance is more evenly distributed.

CAPACITY REACTANCE.--See Reactance, Capacity.

CAPACITY UNIT.--See Farad.

CARBON RHEOSTATS.--See Rheostat, Carbon.

CARBORUNDUM DETECTOR.--See Detector.

CARRIER CURRENT TELEPHONY.--See Wired-Wireless.

CARRIER FREQUENCY.--See Frequency, Carrier.

CARRIER FREQUENCY TELEPHONY.--See Wired-Wireless.

CASCADE AMPLIFICATION.--Two or more amplifying tubes hooked up in a receiving set.

CAT WHISKER CONTACT.--A long, thin wire which makes contact with the crystal of a detector.

CENTIMETER OF CAPACITANCE.--Equal to 1.11 microfarads.

CENTIMETER OF INDUCTANCE.--Equal to one one-thousandth part of a microhenry.

CELLULAR COILS.--See Coils, Inductance.

C.G.S. ELECTROSTATIC UNIT OF CAPACITANCE.--See Centimeter of Capacitance.

CHARACTERISTICS.--The special behavior of a device, such as an aerial, a detector tube, etc.

CHARACTERISTICS, GRID.--See Grid Characteristics.

CHOKE COILS.--Coils that prevent the high voltage oscillations from surging back into the transformer and breaking down the insulation.

CHOPPER MODULATION.--See Modulation, Chopper.

CIRCUIT.--Any electrical conductor through which a current can flow. A low voltage current requires a loop of wire or other conductor both ends of which are connected to the source of current before it can flow. A high frequency current will surge in a wire which is open at both ends like the aerial.

• Closed Circuit.--A circuit that is continuous.
• Open Circuit.--A conductor that is not continuous.
• Coupled Circuits.--Open and closed circuits connected together by inductance coils, condensers or resistances. See coupling.
• Close Coupled Circuits.--Open and closed circuits connected directly together with a single inductance coil.
• Loose Coupled Circuits.--Opened and closed currents connected together inductively by means of a transformer.
• Stand-by Circuits.--Also called pick-up circuits. When listening-in for possible calls from a number of stations, a receiver is used which will respond to a wide band of wave lengths.
• Armstrong Circuits.--The regenerative circuit invented by Major E. H. Armstrong.

CLOSE COUPLED CIRCUITS.--See Currents, Close Coupled.

CLOSED CIRCUIT.--See Circuit, Closed.

CLOSED CORE TRANSFORMER.--See Transformer, Closed Core.

CODE.--

• Continental.--Same as International.
• International.--On the continent of Europe land lines use the Continental Morse alphabetic code. This code has come to be used throughout the world for wireless telegraphy and hence it is now called the International code. It is given on Page 305. [Appendix: International Morse Code].
• Morse.--The code devised by Samuel F. B. Morse and which is used on the land lines in the U. S.
• National Electric.--A set of rules and requirements devised by the National Board of Fire Underwriters for the electrical installations in buildings on which insurance companies carry risks. This code also covers the requirements for wireless installations. A copy may be had from the National Board of Fire Underwriters, New York City, or from your insurance agent.
• National Electric Safety.--The Bureau of Standards, Washington, D. C., have investigated the precautions which should be taken for the safe operation of all electric equipment. A copy of the Bureau of Standards Handbook No. 3 can be had for 40 cents from the Superintendent of Documents.

COEFFICIENT OF COUPLING.--See Coupling, Coefficient of.

COIL AERIAL.--See Aerial, Loop.

COIL ANTENNA.--See Aerial, Loop.

COIL, INDUCTION.--An apparatus for changing low voltage direct currents into high voltage, low frequency alternating currents. When fitted with a spark gap the high voltage, low frequency currents are converted into high voltage, high frequency currents. It is then also called a spark coil and a Ruhmkorff coil.

COIL, LOADING.--A coil connected in the aerial or closed oscillation circuit so that longer wave lengths can be received.

COIL, REPEATING.--See Repeating Coil.

COIL, ROTATING.--One which rotates on a shaft instead of sliding as in a loose coupler. The rotor of a variometer or variocoupler is a rotating coil.

COILS, INDUCTANCE.--These are the tuning coils used for sending and receiving sets. For sending sets they are formed of one and two coils, a single sending coil is generally called a tuning inductance coil, while a two-coil tuner is called an oscillation transformer. Receiving tuning coils are made with a single layer, single coil, or a pair of coils, when it is called an oscillation transformer. Some tuning inductance coils have more than one layer, they are then called lattice wound, cellular, basket wound, honeycomb, duo-lateral, stagger wound, spider-web and slab coils.

COMMERCIAL FREQUENCY.--See Frequency, Commercial.

CONDENSER, AERIAL SERIES.--A condenser placed in the aerial wire system to cut down the wave length.

CONDENSER, VERNIER.--A small variable condenser used for receiving continuous waves where very sharp tuning is desired.

CONDENSER.--All conducting objects with their insulation form capacities, but a condenser is understood to mean two sheets or plates of metal placed closely together but separated by some insulating material.

• Adjustable Condenser.--Where two or more condensers can be coupled together by means of plugs, switches or other devices.
• Aerial Condenser.--A condenser connected in the aerial.
• Air Condenser.--Where air only separates the sheets of metal.
• By-Pass Condenser.--A condenser connected in the transmitting currents so that the high frequency currents cannot flow back through the power circuit.
• Filter Condenser.--A condenser of large capacitance used in combination with a filter reactor for smoothing out the pulsating direct currents as they come from the rectifier.
• Fixed Condenser.--Where the plates are fixed relatively to one another.
• Grid Condenser.--A condenser connected in series with the grid lead.
• Leyden Jar Condenser.--Where glass jars are used.
• Mica Condenser.--Where mica is used.
• Oil Condenser.--Where the plates are immersed in oil.
• Paper Condenser.--Where paper is used as the insulating material.
• Protective.--A condenser of large capacity connected across the low voltage supply circuit of a transmitter to form a by-path of kick-back oscillations.
• Variable Condenser.--Where alternate plates can be moved and so made to interleave more or less with a set of fixed plates.
• Vernier.--A small condenser with a vernier on it so that it can be very accurately varied. It is connected in parallel with the variable condenser used in the primary circuit and is used for the reception of continuous waves where sharp tuning is essential.

CONDENSITE.--A manufactured insulating compound.

CONDUCTIVITY.--The conductance of a given length of wire of uniform cross section. The reciprocal of resistivity.

CONTACT DETECTORS.--See Detectors, Contact.

CONTINENTAL CODE.--See Code, Continental.

COULOMB.--The quantity of electricity transferred by a current of 1 ampere in 1 second.

CONVECTIVE DISCHARGE.--See Discharge.

CONVENTIONAL SIGNALS.--See Signals, Conventional.

COUNTER ELECTROMOTIVE FORCE.--See Electromotive Force, Counter.

COUNTERPOISE. A duplicate of the aerial wire that is raised a few feet above the earth and insulated from it. Usually no connection is made with the earth itself.

COUPLED CIRCUITS.--See Circuit, Coupled.

COUPLING.--When two oscillation circuits are connected together either by the magnetic field of an inductance coil, or by the electrostatic field of a condenser.

COUPLING, CAPACITIVE.--Oscillation circuits when connected together by condensers instead of inductance coils.

COUPLING, COEFFICIENT OF.--The measure of the closeness of the coupling between two coils.

COUPLING, INDUCTIVE.--Oscillation circuits when connected together by inductance coils.

COUPLING, RESISTANCE.--Oscillation circuits connected together by a resistance.

CRYSTAL RECTIFIER.--A crystal detector.

CURRENT, ALTERNATING (A.C.).--A low frequency current that surges to and fro in a circuit.

CURRENT, AUDIO FREQUENCY.--A current whose frequency is low enough to be heard in a telephone receiver. Such a current usually has a frequency of between 200 and 2,000 cycles per second.

CURRENT, PLATE.--The current which flows between the filament and the plate of a vacuum tube.

CURRENT, PULSATING.--A direct current whose voltage varies from moment to moment.

CURRENT, RADIO FREQUENCY.--A current whose frequency is so high it cannot be heard in a telephone receiver. Such a current may have a frequency of from 20,000 to 10,000,000 per second.

CURRENTS, HIGH FREQUENCY.--(1) Currents that oscillate from 10,000 to 300,000,000 times per second. (2) Electric oscillations.

CURRENTS, HIGH POTENTIAL.--(1) Currents that have a potential of more than 10,000 volts. (2) High voltage currents.

CYCLE.--(1) A series of changes which when completed are again at the starting point. (2) A period of time at the end of which an alternating or oscillating current repeats its original direction of flow.

DAMPING.--The degree to which the energy of an electric oscillation is reduced. In an open circuit the energy of an oscillation set up by a spark gap is damped out in a few swings, while in a closed circuit it is greatly prolonged, the current oscillating 20 times or more before the energy is dissipated by the sum of the resistances of the circuit.

DECREMENT.--The act or process of gradually becoming less.

DETECTOR.--Any device that will (1) change the oscillations set up by the incoming waves into direct current, that is which will rectify them, or (2) that will act as a relay.

• Carborundum.--One that uses a carborundum crystal for the sensitive element. Carborundum is a crystalline silicon carbide formed in the electric furnace.
• Cat Whisker Contact.--See Cat Whisker Contact.
• Chalcopyrite.--Copper pyrites. A brass colored mineral used as a crystal for detectors. See Zincite.
• Contact.--A crystal detector. Any kind of a detector in which two dissimilar but suitable solids make contact.
• Ferron.--A detector in which iron pyrites are used as the sensitive element.
• Galena.--A detector that uses a galena crystal for the rectifying element.
• Iron Pyrites.--A detector that uses a crystal of iron pyrites for its sensitive element.
• Molybdenite.--A detector that uses a crystal of sulphide of molybdenum for the sensitive element.
• Perikon.--A detector in which a bornite crystal makes contact with a zincite crystal.
• Silicon.--A detector that uses a crystal of silicon for its sensitive element.
• Vacuum Tube.--A vacuum tube (which see) used as a detector.
• Zincite.--A detector in which a crystal of zincite is used as the sensitive element.

DE TUNING.--A method of signaling by sustained oscillations in which the key when pressed down cuts out either some of the inductance or some of the capacity and hence greatly changes the wave length.

DIELECTRIC.--An insulating material between two electrically charged plates in which there is set up an electric strain, or displacement.

DIELECTRIC STRAIN.--The electric displacement in a dielectric.

DIRECTIONAL AERIAL.--See Aerial, Directional.

DIRECTION FINDER.--See Aerial, Loop.

DISCHARGE.--(1) A faintly luminous discharge that takes place from the positive pointed terminal of an induction coil, or other high potential apparatus; is termed a brush discharge. (2) A continuous discharge between the terminals of a high potential apparatus is termed a convective discharge. (3) The sudden breaking-down of the air between the balls forming the spark gap is termed a disruptive discharge; also called an electric spark, or just spark for short. (4) When a tube has a poor vacuum, or too large a battery voltage, it glows with a blue light and this is called a blue glow discharge.

DISRUPTIVE DISCHARGE.--See Discharge.

DISTRESS CALL. [Morse code:] ...---... (SOS).

DISTRIBUTED CAPACITY.--See Capacity, Distributed.

DOUBLE HUMP RESONANCE CURVE.--A resonance curve that has two peaks or humps which show that the oscillating currents which are set up when the primary and secondary of a tuning coil are closely coupled have two frequencies.

DUO-LATERAL COILS.--See Coils, Inductance.

DUPLEX COMMUNICATION.--A wireless telephone system with which it is possible to talk between both stations in either direction without the use of switches. This is known as the duplex system.

EARTH CAPACITY.--An aerial counterpoise.

EARTH CONNECTION.--Metal plates or wires buried in the ground or immersed in water. Any kind of means by which the sending and receiving apparatus can be connected with the earth.

EDISON STORAGE BATTERY.--See Storage Battery, Edison.

ELECTRIC ENERGY.--The power of an electric current.

ELECTRIC OSCILLATIONS.--See Oscillations, Electric.

ELECTRIC SPARK.--See Discharge, Spark.

ELECTRICITY, NEGATIVE.--The opposite of positive electricity. Negative electricity is formed of negative electrons which make up the outside particles of an atom.

ELECTRICITY, POSITIVE.--The opposite of negative electricity. Positive electricity is formed of positive electrons which make up the inside particles of an atom.

ELECTRODES.--Usually the parts of an apparatus which dip into a liquid and carry a current. The electrodes of a dry battery are the zinc and carbon elements. The electrodes of an Edison storage battery are the iron and nickel elements, and the electrodes of a lead storage battery are the lead elements.

ELECTROLYTES.--The acid or alkaline solutions used in batteries.

ELECTROMAGNETIC WAVES.--See Waves, Electric.

ELECTROMOTIVE FORCE.--Abbreviated emf. The force that drives an electric current along a conductor. Also loosely called voltage.

ELECTROMOTIVE FORCE, COUNTER.--The emf. that is set up in a direction opposite to that in which the current is flowing in a conductor.

ELECTRON.--(1) A negative particle of electricity that is detached from an atom. (2) A negative particle of electricity thrown off from the incandescent filament of a vacuum tube.

ELECTRON FLOW.--The passage of electrons between the incandescent filament and the cold positively charged plate of a vacuum tube.

ELECTRON RELAY.--See Relay, Electron.

ELECTRON TUBE.--A vacuum tube or a gas-content tube used for any purpose in wireless work. See Vacuum Tube.

ELECTROSE INSULATORS.--Insulators made of a composition material the trade name of which is Electrose.

ENERGY, ELECTRIC.--See Electric Energy.

ENERGY UNIT.--The joule, which see, Page 308 [Appendix: Definitions of Electric and Magnetic Units].

FADING.--The sudden variation in strength of signals received from a transmitting station when all the adjustments of both sending and receiving apparatus remain the same. Also called swinging.

FARAD.--The capacitance of a condenser in which a potential difference of 1 volt causes it to have a charge of 1 coulomb of electricity.

FEED-BACK ACTION.--Feeding back the oscillating currents in a vacuum tube to amplify its power. Also called regenerative action.

FERROMAGNETIC CONTROL.--See Magnetic Amplifier.

FILAMENT.--The wire in a vacuum tube that is heated to incandescence and which throws off electrons.

FILAMENT RHEOSTAT.--See Rheostat, Filament.

FILTER.--Inductance coils or condensers or both which (1) prevent troublesome voltages from acting on the different circuits, and (2) smooth out alternating currents after they have been rectified.

FILTER REACTOR.--See Reactor, Filter.

FIRE UNDERWRITERS.--See Code, National Electric.

FIXED GAP.--See Gap.

FLEMING VALVE.--A two-electrode vacuum tube.

FORCED OSCILLATIONS.--See Oscillations, Forced.

FREE OSCILLATIONS.--See Oscillations, Free.

FREQUENCY, AUDIO.--(1) An alternating current whose frequency is low enough to operate a telephone receiver and, hence, which can be heard by the ear. (2) Audio frequencies are usually around 500 or 1,000 cycles per second, but may be as low as 200 and as high as 10,000 cycles per second.

• Carrier.--A radio frequency wave modulated by an audio frequency wave which results in setting of three radio frequency waves. The principal radio frequency is called the carrier frequency, since it carries or transmits the audio frequency wave.
• Commercial.--(1) Alternating current that is used for commercial purposes, namely, light, heat and power. (2) Commercial frequencies now in general use are from 25 to 50 cycles per second.
• Natural.--The pendulum and vibrating spring have a natural frequency which depends on the size, material of which it is made, and the friction which it has to overcome. Likewise an oscillation circuit has a natural frequency which depends upon its inductance, capacitance and resistance.
• Radio.--(1) An oscillating current whose frequency is too high to affect a telephone receiver and, hence, cannot be heard by the ear. (2) Radio frequencies are usually between 20,000 and 2,000,000 cycles per second but may be as low as 10,000 and as high as 300,000,000 cycles per second.
• Spark.--The number of sparks per second produced by the discharge of a condenser.

GAP, FIXED.--One with fixed electrodes.

GAP, NON-SYNCHRONOUS.--A rotary spark gap run by a separate motor which may be widely different from that of the speed of the alternator.

GAP, QUENCHED.--(1) A spark gap for the impulse production of oscillating currents. (2) This method can be likened to one where a spring is struck a single sharp blow and then continues to set up vibrations.

GAP, ROTARY.--One having fixed and rotating electrodes.

GAP, SYNCHRONOUS.--A rotary spark gap run at the same speed as the alternator which supplies the power transformer. Such a gap usually has as many teeth as there are poles on the generator. Hence one spark occurs per half cycle.

GAS-CONTENT TUBE.--See Vacuum Tube.

GENERATOR TUBE.--A vacuum tube used to set up oscillations. As a matter of fact it does not generate oscillations, but changes the initial low voltage current that flows through it into oscillations. Also called an oscillator tube and a power tube.

GRID BATTERY.--See Battery C.

GRID CHARACTERISTICS.--The various relations that could exist between the voltages and currents of the grid of a vacuum tube, and the values which do exist between them when the tube is in operation. These characteristics are generally shown by curves.

GRID CONDENSER.--See Condenser, Grid.

GRID LEAK.--A high resistance unit connected in the grid lead of both sending and receiving sets. In a sending set it keeps the voltage of the grid at a constant value and so controls the output of the aerial. In a receiving set it controls the current flowing between the plate and filament.

GRID MODULATION.--See Modulation, Grid.

GRID POTENTIAL.--The negative or positive voltage of the grid of a vacuum tube.

GRID VOLTAGE.--See Grid Potential.