The Operation of C. W. Telegraph Transmitters with Direct Current.—The chief differences between the long distance sets which use a direct current, i.e., those described in Chapter XVI, and the short distance transmitting sets are that the former use: (1) a motor-generator set for changing the low voltage direct current into high voltage direct current, and (2) a chopper in the key circuit. The way the motor-generator changes the low- into high-voltage current has been explained in Chapter XVI.

The chopper interrupts the oscillations surging through the grid circuit at a frequency that the ear can hear, that is to say, about 800 to 1,000 times per second. When the key is open, of course, the sustained oscillations set up in the circuits will send out continuous waves but when the key is closed these oscillations are broken up and then they send out discontinuous waves. If a heterodyne receiving set, see Chapter XV, is being used at the other end you can dispense with the chopper and the key circuit needed is very much simplified. The operation of key circuits of the latter kind will be described presently.

The Operation of C. W. Telegraph Transmitters with Alternating Current—With a Single Oscillator Tube.—Where an oscillator tube telegraph transmitter is operated by a 110 volt alternating current as the initial source of energy, a buzzer, chopper or other interruptor is not needed in the key circuit. This is because oscillations are set up only when the plate is energized with the positive part of the alternating current and this produces an intermittent musical tone in the headphones. Hence this kind of a sending set is called a tone transmitter.

Since oscillations are set up only by the positive part or voltage of an alternating current it is clear that, as a matter of fact, this kind of a transmitter does not send out continuous waves and therefore it is not a C. W. transmitter. This is graphically shown by the curve of the wave form of the alternating current and the oscillations that are set up by the positive part of it in Fig. 95. Whenever the positive half of the alternating current energizes the plate then oscillations are set up by the tube and, conversely, when the negative half of the current charges the plate no oscillations are produced.



You will also observe that the oscillations set up by the positive part of the current are not of constant amplitude but start at zero the instant the positive part begins to energize the plate and they keep on increasing in amplitude as the current rises in voltage until the latter reaches its maximum; then as it gradually drops again to zero the oscillations decrease proportionately in amplitude with it.

Heating the Filament with Alternating Current.—Where an alternating current power transformer is used to develop the necessary plate voltage a second secondary coil is generally provided for heating the filament of the oscillation tube. This is better than a direct current for it adds to the life of the filament. When you use an alternating current to heat the filament keep it at the same voltage rather than at the same amperage (current strength). To do this you need only to use a voltmeter across the filament terminals instead of an ammeter in series with it; then regulate the voltage of the filament with a rheostat.

The Operation of C. W. Telegraph Transmitters with Alternating Current—With Two Oscillator Tubes.—By using two oscillator tubes and connecting them up with the power transformer and oscillating circuits as shown in the wiring diagram in Fig. 83 the plates are positively energized alternately with every reversal of the current and, consequently, there is no time period between the ending of the oscillations set up by one tube and the beginning of the oscillations set up by the other tube. In other words these oscillations are sustained but as in the case of those of a single tube, their amplitude rises and falls. This kind of a set is called a full wave rectification transmitter.

The waves radiated by this transmitter can be received by either a crystal detector or a plain vacuum-tube detector but the heterodyne receptor will give you better results than either of the foregoing types.

The Operation of Wireless Telephone Transmitters with Direct Current—Short Distance Transmitter.—The operation of this short distance wireless telephone transmitter, a wiring diagram of which is shown in Fig. 85 is exactly the same as that of the Direct Current Short Distance C. W. Telegraph Transmitter already explained in this chapter. The only difference in the operation of these sets is the substitution of the microphone transmitter for the telegraph key.

The Microphone Transmitter.—The microphone transmitter that is used to vary, or modulate, the sustained oscillations set up by the oscillator tube and circuits is shown in Fig. 84. By referring to the diagram at A in this figure you will readily understand how it operates. When you speak into the mouthpiece the sound waves, which are waves in the air, impinge upon the diaphragm and these set it into vibration—that is, they make it move to and fro.

When the diaphragm moves toward the back of the transmitter it forces the carbon granules that are in the cup closer together; this lowers their resistance and allows more current from the battery to flow through them; when the pressure of the air waves is removed from the diaphragm it springs back toward the mouth-piece and the carbon granules loosen up when the resistance offered by them is increased and less current can flow through them. Where the oscillation current in the aerial wire is small the transmitter can be connected directly in series with the latter when the former will surge through it. As you speak into the microphone transmitter its resistance is varied and the current strength of the oscillations is varied accordingly.

The Operation of Wireless Telephone Transmitters with Direct Current—Long Distance Transmitters.—In the wireless telephone transmitters for long distance work which were shown and described in the preceding chapter a battery is used to energize the microphone transmitter, and these two elements are connected in series with a microphone modulator. This latter device may be either (1) a telephone induction coil, (2) a microphone transformer, or (3) a magnetic modulator; the first two of these devices step-up the voltage of the battery current and the amplified voltage thus developed is impressed on the oscillations that surge through the closed oscillation circuit or the aerial wire system according to the place where you connect it. The third device works on a different principle and this will be described a little farther along.

The Operation of Microphone Modulators—The Induction Coil.—This device is really a miniature transformer, see A in Fig. 86, and its purpose is to change the 6 volt direct current that flows through the microphone into 100 volts alternating current; in turn, this is impressed on the oscillations that are surging in either (1) the grid circuit as shown at A in Fig. 89, and in Fig. 90, (2) the aerial wire system, as shown at B in Fig. 89 and Fig. 93. When the current from the battery flows through the primary coil it magnetizes the soft iron core and as the microphone varies the strength of the current the high voltage alternating currents set up in the secondary coil of the induction coil are likewise varied, when they are impressed upon and modulate the oscillating currents.

The Microphone Transformer.—This is an induction coil that is designed especially for wireless telephone modulation. The iron core of this transformer is also of the open magnetic circuit type, see A in Fig. 87, and the ratio of the turns [Footnote: See Chapter VI] of the primary and the secondary coil is such that when the secondary current is impressed upon either the grid circuit or the aerial wire system it controls the oscillations flowing through it with the greatest efficiency.

The Magnetic Modulator.—This piece of apparatus is also called a magnetic amplifier. The iron core is formed of very thin plates, or laminations as they are called, and this permits high-frequency oscillations to surge in a coil wound on it. In this transformer, see A in Fig. 88, the current flowing through the microphone varies the magnetic permeability of the soft iron core by the magnetic saturation of the latter. Since the microphone current is absolutely distinct from the oscillating currents surging through the coil of the transformer a very small direct current flowing through a coil on the latter will vary or modulate very large oscillating currents surging through the former. It is shown connected in the aerial wire system at A in Fig. 88, and in Fig. 93.

Operation of the Vacuum Tube as a Modulator.—Where a microphone modulator of the induction coil or microphone transformer type is connected in the grid circuit or aerial wire system the modulation is not very effective, but by using a second tube as a modulator, as shown in Fig. 90, an efficient degree of modulation can be had. Now there are two methods by which a vacuum tube can be used as a modulator and these are: (1) by the absorption of the energy of the current set up by the oscillator tube, and (2) by varying the direct current that energizes the plate of the oscillator tube.

The first of these two methods is not used because it absorbs the energy of the oscillating current produced by the tube and it is therefore wasteful. The second method is an efficient one, as the direct current is varied before it passes into the oscillator tube. This is sufficient reason for describing only the second method. The voltage of the grid of the modulator tube is varied by the secondary coil of the induction coil or microphone transformer, above described. In this way the modulator tube acts like a variable resistance but it amplifies the variations impressed on the oscillations set up by the oscillator tube. As the magnetic modulator does the same thing a vacuum tube used as a modulator is not needed where the former is employed. For this reason a magnetic modulator is the cheapest in the long run.

The Operation of Wireless Telephone Transmitters with Alternating Current.—Where an initial alternating current is used for wireless telephony, the current must be rectified first and then smoothed out before passing into the oscillator tube to be converted into oscillations. Further so that the oscillations will be sustained, two oscillator tubes must be used, and, finally, in order that the oscillations may not vary in amplitude the alternating current must be first changed into direct current by a pair of rectifier vacuum tubes, as shown in Fig. 93. When this is done the plates will be positively charged alternately with every reversal of the current in which case there will be no break in the continuity of the oscillations set up and therefore in the waves that are sent out.

The Operation of Rectifier Vacuum Tubes.—The vacuum tube rectifier is simply a two electrode vacuum tube. The way in which it changes a commercial alternating current into pulsating direct current is the same as that in which a two electrode vacuum tube detector changes an oscillating current into pulsating direct currents and this has been explained in detail under the heading of The Operation of a Two Electrode Vacuum Tube Detector in Chapter XII. In the C. W. Telegraph Transmitting Sets described in Chapter XVII, the oscillator tubes act as rectifiers as well as oscillators but for wireless telephony the alternating current must be rectified first so that a continuous direct current will result.

The Operation of Reactors and Condensers.—A reactor is a single coil of wire wound on an iron core, see Fig. 90 and A in Fig. 91, and it should preferably have a large inductance. The reactor for the plate and grid circuit of a wireless telephone transmitter where one or more tubes are used as modulators as shown in the wiring diagram in Fig. 90, and the filter reactor shown in Fig. 92, operate in the same way.

When an alternating current flows through a coil of wire the reversals of the current set up a counter electromotive force in it which opposes, that is reacts, on the current, and the higher the frequency of the current the greater will be the reactance. When the positive half of an alternating current is made to flow through a large resistance the current is smoothed out but at the same time a large amount of its energy is used up in producing heat.

But when the positive half of an alternating current is made to flow through a large inductance it acts like a large resistance as before and likewise smooths out the current, but none of its energy is wasted in heat and so a coil having a large inductance, which is called an inductive reactance, or just reactor for short, is used to smooth out, or filter, the alternating current after it has been changed into a pulsating direct current by the rectifier tubes.

A condenser also has a reactance effect on an alternating current but different from an induction coil the lower the frequency the greater will be the reactance. For this reason both a filter reactor and filter condensers are used to smooth out the pulsating direct currents.



CHAPTER XX

HOW TO MAKE A RECEIVING SET FOR $5.00 OR LESS

In the chapters on Receptors you have been told how to build up high-grade sets. But there are thousands of boys, and, probably, not a few men, who cannot afford to invest $25.00, more or less, in a receiving set and would like to experiment in a small way.

The following set is inexpensive, and with this cheap, little portable receptor you can get the Morse code from stations a hundred miles distant and messages and music from broadcasting stations if you do not live too far away from them. All you need for this set are: (1) a crystal detector, (2) a tuning coil and (3) an earphone. You can make a crystal detector out of a couple of binding posts, a bit of galena and a piece of brass wire, or, better, you can buy one all ready to use for 50 cents.



The Crystal Detector.—This is known as the Rasco baby detector and it is made and sold by the Radio Specialty Company, 96 Park Place, New York City. It is shown in Fig. 96. The base is made of black composition and on it is mounted a standard in which a rod slides and on one end of this there is fixed a hard rubber adjusting knob while the other end carries a thin piece of phosphor-bronze wire, called a cat-whisker. To secure the galena crystal in the cup you simply unscrew the knurled cap, place it in the cavity of the post and screw the cap back on again. The free end of the cat-whisker wire is then adjusted so that it will rest lightly on the exposed part of the galena.



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

Unit Abbreviation

ampere amp. ampere-hours amp.-hr. centimeter cm. centimeter-gram-second c.g.s. cubic centimeters cm.^3 cubic inches cu. in. cycles per second ~ degrees Centigrade C. degrees Fahrenheit F. feet ft. foot-pounds ft.-lb. grams g. henries h. inches in. kilograms kg. kilometers km. kilowatts kw. kilowatt-hours kw.-hr. kilovolt-amperes kv.-a. meters m. microfarads [Greek: mu]f. micromicrofarads [Greek: mu mu]f. millihenries mh. millimeters mm. pounds lb. seconds sec. square centimeters cm.^2 square inches sq. in. volts v. watts w.

PREFIXES USED WITH METRIC SYSTEM UNITS

Prefix Abbreviation Meaning

micro [Greek: mu]. 1 millionth milli m. 1 thousandth centi c. 1 hundredth deci d. 1 tenth deka dk. 10 hekto h. 1 hundred kilo k. 1 thousand mega m. 1 million



SYMBOLS USED FOR VARIOUS QUANTITIES

Quantity Symbol

capacitance C

conductance g

coupling co-efficient k

current, instantaneous i

current, effective value I

decrement [Greek: delta]

dielectric constant [Greek: alpha]

electric field intensity [Greek: epsilon]

electromotive force, instantaneous value E

electromotive force, effective value F

energy W

force F

frequency f

frequency x 2[Greek: pi] [Greek: omega]

impedance Z

inductance, self L

inductance, mutual M

magnetic field intensity A

magnetic flux [Greek: Phi]

magnetic induction B

period of a complete oscillation T

potential difference V

quantity of electricity Q

ratio of the circumference of a circle to its diameter =3.1416 [Greek: pi]

reactance X

resistance R

time t

velocity v

velocity of light c

wave length [Greek: lambda]

wave length in meters [Greek: lambda]m

work W

permeability [Greek: mu]

Square root [Math: square root]



TABLE OF ENAMELED WIRE

No. of Turns Turns Ohms per Wire, per per Cubic Inch B.& S. Linear Square of Gauge Inch Inch Winding

20 30 885 .748

22 37 1400 1.88

24 46 2160 4.61

26 58 3460 11.80

28 73 5400 29.20

30 91 8260 70.90

32 116 21,000 7547.00

34 145 13,430 2968.00

36 178 31,820 1098.00

38 232 54,080 456.00

40 294 86,500 183.00



TABLE OF FREQUENCY AND WAVE LENGTHS

W. L.—Wave Lengths in Meters. F.—Number of Oscillations per Second. O. or square root L. C. is called Oscillation Constant. C.—Capacity in Microfarads. L.—Inductance in Centimeters. 1000 Centimeters = 1 Microhenry.

W.L. F O L.C. 50 6,000,000 .839 .7039 100 3,000,000 1.68 2.82 150 2,000,000 2.52 6.35 200 1,500,000 3.36 11.29 250 1,200,000 4.19 17.55 300 1,000,000 5.05 25.30 350 857,100 5.87 34.46 400 750,000 6.71 45.03 450 666,700 7.55 57.00 500 600,000 8.39 70.39 550 545,400 9.23 85.19 600 500,000 10.07 101.41 700 428,600 11.74 137.83 800 375,000 13.42 180.10 900 333,300 15.10 228.01 1,000 300,000 16.78 281.57 1,100 272,730 18.45 340.40 1,200 250,000 20.13 405.20 1,300 230,760 21.81 475.70 1,400 214,380 23.49 551.80 1,500 200,000 25.17 633.50 1,600 187,500 26.84 720.40 1,700 176,460 28.52 813.40 1,800 166,670 30.20 912.00 1,900 157,800 31.88 1,016.40 2,000 150,000 33.55 1,125.60 2,100 142,850 35.23 1,241.20 2,200 136,360 36.91 1,362.40 2,300 130,430 38.59 1,489.30 2,400 125,000 40.27 1,621.80 2,500 120,000 41.95 1,759.70 2,600 115,380 43.62 1,902.60 2,700 111,110 45.30 2,052.00 2,800 107,140 46.89 2,207.00 2,900 103,450 48.66 2,366.30 3,000 100,000 50.33 2,533.20 4,000 75,000 67.11 4,504.00 5,000 60,000 83.89 7,038.00 6,000 50,000 100.7 10,130.00 7,000 41,800 117.3 13,630.00 8,000 37,500 134.1 18,000.00 9,000 33,300 151.0 22,820.00 10,000 30,000 167.9 28,150.00 11,000 27,300 184.8 34,150.00 12,000 25,000 201.5 40,600.00 13,000 23,100 218.3 47,600.00 14,000 21,400 235.0 55,200.00 15,000 20,000 252.0 63,500.00 16,000 18,750 269.0 72,300.00



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:

a alpha b beta g gamma d delta e epsilon z zeta ae eta th theta i iota k kappa l lambda m mu n nu x Xi(Zi) o omicron p pi r rho s sigma t tau u upsilon ph phi ch chi ps psi o omega



TABLE OF SPARKING DISTANCES

In Air for Various Voltages between Needle Points

Volts Distance Inches Centimeter 5,000 .225 .57 10,000 .470 1.19 15,000 .725 1.84 20,000 1.000 2.54 25,000 1.300 3.30 30,000 1.625 4.10 35,000 2.000 5.10 40,000 2.450 6.20 45,000 2.95 7.50 50,000 3.55 9.90 60,000 4.65 11.8 70,000 5.85 14.9 80,000 7.10 18.0 90,000 8.35 21.2 100,000 9.60 24.4 110,000 10.75 27.3 120,000 11.85 30.1 130,000 12.95 32.9 140,000 13.95 35.4 150,000 15.00 38.1

FEET PER POUND OF INSULATED MAGNET WIRE

No. of Single Double Single Double B.& S. Cotton, Cotton, Silk, Silk, Enamel Gauge 4-Mils 8-Mils 1-3/4-Mils 4-Mils

20 311 298 319 312 320 21 389 370 408 389 404 22 488 461 503 498 509 23 612 584 636 631 642 24 762 745 800 779 810 25 957 903 1,005 966 1,019 26 1,192 1,118 1,265 1,202 1,286 27 1,488 1,422 1,590 1,543 1,620 28 1,852 1,759 1,972 1,917 2,042 29 2,375 2,207 2,570 2,435 2,570 30 2,860 2,534 3,145 2,900 3,240 31 3,800 2,768 3,943 3,683 4,082 32 4,375 3,737 4,950 4,654 5,132 33 5,590 4,697 6,180 5,689 6,445 34 6,500 6,168 7,740 7,111 8,093 35 8,050 6,737 9,600 8,584 10,197 36 9,820 7,877 12,000 10,039 12,813 37 11,860 9,309 15,000 10,666 16,110 38 14,300 10,636 18,660 14,222 20,274 39 17,130 11,907 23,150 16,516 25,519 40 21,590 14,222 28,700 21,333 32,107



INTERNATIONAL MORSE CODE AND CONVENTIONAL SIGNALS

TO BE USED FOR ALL GENERAL PUBLIC SERVICE RADIO COMMUNICATION

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]

A .-

B -...

C -.-.

D -..

E .

F ..-.

G —.

H ....

I ..

J .—-

K -.-

L .-..

M —

N -.

O —-

P .—.

Q —.-

R .-.

S ...

T -

U ..-

V ...-

W .—

X -..-

Y -.—

Z —..

(German) .-.-

or (Spanish-Scandinavian) .—.-

CH (German-Spanish) ——

(French) ..-..

(Spanish) —.—

(German) —-.

(German) ..—

1 .——

2 ..—-

3 ...—

4 ....-

5 .....

6 -....

7 —...

8 —-..

9 ——.

0 ——-

Period .. .. ..

Semicolon -.-.-.

Comma -.-.-.

Colon —-...

Interrogation ..—..

Exclamation point —..—

Apostrophe .——.

Hyphen -....-

Bar indicating fraction -..-.

Parenthesis -.—.-

Inverted commas .-..-.

Underline ..—.-

Double dash -...-

Distress Call ...—-...

Attention call to precede every transmission -.-.-

General inquiry call -.-. —.-

From (de) -.. .

Invitation to transmit (go ahead) -.-

Warning—high power —..—

Question (please repeat after ...)—interrupting long messages ..—..

Wait .-...

Break (Bk.) (double dash) -...-

Understand ...-.

Error ........

Received (O.K.) .-.

Position report (to precede all position messages) - .-.

End of each message (cross) .-.-.

Transmission finished (end of work) (conclusion of correspondence) ...-.-



INTERNATIONAL RADIOTELEGRAPHIC CONVENTION

LIST OF ABBREVIATIONS TO BE USED IN RADIO COMMUNICATION

ABBREVIATION QUESTION ANSWER OR REPLY

PRB Do you wish to communicate I wish to communicate by means by means of the International of the International Signal Code. Signal Code?

QRA What ship or coast station is This is.... that?

QRB What is your distance? My distance is....

QRC What is your true bearing? My true bearing is....

QRD Where are you bound for? I am bound for....

QRF Where are you bound from? I am bound from....

QRG What line do you belong to? I belong to the ... Line.

QRH What is your wave length in My wave length is ... meters. meters?

QRJ How many words have you to send? I have ... words to send.

QRK How do you receive me? I am receiving well.

QRL Are you receiving badly? I am receiving badly. Please Shall I send 20? send 20. ...-. ...-. for adjustment? for adjustment.

QRM Are you being interfered with? I am being interfered with.

QRN Are the atmospherics strong? Atmospherics are very strong.

QRO Shall I increase power? Increase power.

QRP Shall I decrease power? Decrease power.

QRQ Shall I send faster? Send faster.

QRS Shall I send slower? Send slower.

QRT Shall I stop sending? Stop sending.

QRU Have you anything for me? I have nothing for you.

QRV Are you ready? I am ready. All right now.

QRW Are you busy? I am busy (or: I am busy with...). Please do not interfere.

QRX Shall I stand by? Stand by. I will call you when required.

QRY When will be my turn? Your turn will be No....

QRZ Are my signals weak? You signals are weak.

QSA Are my signals strong? You signals are strong.

QSB Is my tone bad? The tone is bad. Is my spark bad? The spark is bad.

QSC Is my spacing bad? Your spacing is bad.

QSD What is your time? My time is....

QSF Is transmission to be in Transmission will be in alternate order or in series? alternate order.

QSG Transmission will be in a series of 5 messages.

QSH Transmission will be in a series of 10 messages.

QSJ What rate shall I collect for...? Collect....

QSK Is the last radiogram canceled? The last radiogram is canceled.

QSL Did you get my receipt? Please acknowledge.

QSM What is your true course? My true course is...degrees.

QSN Are you in communication with land? I am not in communication with land.

QSO Are you in communication with I am in communication with... any ship or station (through...). (or: with...)?

QSP Shall I inform...that you are Inform...that I am calling him. calling him?

QSQ Is...calling me? You are being called by....

QSR Will you forward the radiogram? I will forward the radiogram.

QST Have you received the general General call to all stations. call?

QSU Please call me when you have Will call when I have finished. finished (or: at...o'clock)?

QSV Is public correspondence being Public correspondence is being handled? handled. Please do not interfere.

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

QSW Shall I increase my spark Increase your spark frequency. frequency?

QSX Shall I decrease my spark Decrease your spark frequency. frequency?

QSY Shall I send on a wavelength Let us change to the wave length of ... meters? of ... meters.

QSZ Send each word twice. I have difficulty in receiving you.

QTA Repeat the last radiogram.

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.

A. Frederick Collins.—Wireless Telegraphy, Its History, Theory, and Practice. 1905. McGraw Pub. Co., New York City.

J. H. Dellinger.—Principles Underlying Radio Communication. 1921. Signal Corps, U. S. Army, Washington, D. C.

H. M. Dorsett.—Wireless Telegraphy and Telephony. 1920. Wireless Press, Ltd., London.

J. 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

A. ..............Aerial

A.C. ............Alternating Current

A.F. ............Audio Frequency

B. and S. .......Brown & Sharpe Wire Gauge

C. ..............Capacity or Capacitance

C.G.S. ..........Centimeter-Grain-Second

Cond. ...........Condenser

Coup. ...........Coupler

C.W. ............Continuous Waves

D.C. ............Direct Current

D.P.D.T. ........Double Point Double Throw

D.P.S.T. ........Double Point Single Throw

D.X. ............Distance

E. ..............Short for Electromotive Force (Volt)

E.M.F. ..........Electromotive Force

F. ..............Filament or Frequency

G. ..............Grid

Gnd. ............Ground

I. ..............Current Strength (Ampere)

I.C.W. ..........Interrupted Continuous Waves

KW. .............Kilowatt

L. ..............Inductance

L.C. ............Loose Coupler

Litz. ...........Litzendraht

Mfd. ............Microfarad

Neg. ............Negative

O.T. ............Oscillation Transformer

P. ..............Plate

Prim. ...........Primary

Pos. ............Positive

R. ..............Resistance

R.F. ............Radio Frequency

Sec. ............Secondary

S.P.D.T. ........Single Point Double Throw

S.P.S.T. ........Single Point Single Throw

S.R. ............Self Rectifying

T. ..............Telephone or Period (time) of Complete Oscillation

Tick. ...........Tickler

V. ..............Potential Difference

Var. ............Variometer

Var. Cond. ......Variable Condenser

V.T. ............Vacuum Tube

W.L. ............Wave Length

X. ..............Reactance



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.

GRINDERS.—The most common form of Static, which see. They make a grinding noise in the headphones.

GROUND.—See Earth Connection.

GROUND, AMATEUR.—A water-pipe ground.

GROUND, WATERPIPE.—A common method of grounding by amateurs is to use the waterpipe, gaspipe or radiator.

GUIDED WAVE TELEPHONY.—See Wired Wireless.

HARD TUBE.—A vacuum tube in which the vacuum is high, that is, exhausted to a high degree.

HELIX.—(1) Any coil of wire. (2) Specifically a transmitter tuning inductance coil.

HENRY.—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.

HETERODYNE RECEPTION.—(1) Receiving by the beat method. (2) Receiving by means of superposing oscillations generated at the receiving station on the oscillations set up in the aerial by the incoming waves.

HETERODYNE RECEPTOR.—See Receptor, Heterodyne.

HIGH FREQUENCY CURRENTS.—See Currents, High Frequency.

HIGH FREQUENCY RESISTANCE.—See Resistance, High Frequency.

HIGH POTENTIAL CURRENTS.—See Currents, High Potential.

HIGH VOLTAGE CURRENTS.—See Currents, High Potential.

HONEYCOMB COILS.—See Coils, Inductance.

HORSE-POWER.—Used in rating steam machinery. It is equal to 746 watts.

HOT WIRE AMMETER.—See Ammeter, Hot Wire.

HOWLING.—Where more than three stages of radio amplification, or more than two stages of audio amplification, are used howling noises are apt to occur in the telephone receivers.

IMPEDANCE.—An oscillation circuit has reactance and also resistance, and when these are combined the total opposition to the current is called impedance.

INDUCTANCE COILS.—See Coils, Inductance.

INDUCTANCE COIL, LOADING.—See Coil, Loading Inductance.

INDUCTIVE COUPLING.—See Coupling, Inductive.

INDUCTIVE REACTANCE.—See Reactance, Inductive.

INDUCTION COIL.—See Coil, Induction.

INDUCTION, MUTUAL.—Induction produced between two circuits or coils close to each other by the mutual interaction of their magnetic fields.

INSULATION.—Materials used on and around wires and other conductors to keep the current from leaking away.

INSPECTOR, RADIO.—A U. S. inspector whose business it is to issue both station and operators' licenses in the district of which he is in charge.

INTERFERENCE.—The crossing or superposing of two sets of electric waves of the same or slightly different lengths which tend to oppose each other. It is the untoward interference between electric waves from different stations that makes selective signaling so difficult a problem.

INTERMEDIATE WAVES.—See Waves.

IONIC TUBES.—See Vacuum Tubes.

INTERNATIONAL CODE.—See Code, International.

JAMMING.—Waves that are of such length and strength that when they interfere with incoming waves they drown them out.

JOULE.—The energy spent in 1 second by a flow of 1 ampere in 1 ohm.

JOULE'S LAW.—The relation between the heat produced in seconds to the resistance of the circuit, to the current flowing in it.

KENOTRON.—The trade name of a vacuum tube rectifier made by the Radio Corporation of America.

KICK-BACK.—Oscillating currents that rise in voltage and tend to flow back through the circuit that is supplying the transmitter with low voltage current.

KICK-BACK PREVENTION.—See Prevention, Kick-Back.

KILOWATT.—1,000 watts.

LAMBDA.—See Pages 301, 302. [Appendix: Useful Abbreviations].

LATTICE WOUND COILS.—See Coils, Inductance.

LIGHTNING SWITCH.—See Switch, Lightning.

LINE RADIO COMMUNICATION.—See Wired Wireless.

LINE RADIO TELEPHONY.—See Telephony, Line Radio.

LITZENDRAHT.—A conductor formed of a number of fine copper wires either twisted or braided together. It is used to reduce the skin effect. See Resistance, High Frequency.

LOAD FLICKER.—The flickering of electric lights on lines that supply wireless transmitting sets due to variations of the voltage on opening and closing the key.

LOADING COIL.—See Coil, Loading.

LONG WAVES.—See Waves.

LOOP AERIAL.—See Aerial, Loop.

LOOSE COUPLED CIRCUITS.—See Circuits, Loose Coupled.

LOUD SPEAKER.—A telephone receiver connected to a horn, or a specially made one, that reproduces the incoming signals, words or music loud enough to be heard by a room or an auditorium full of people, or by large crowds out-doors.

MAGNETIC POLES.—See Poles, Magnetic.

MEGOHM.—One million ohms.

METER, AUDIBILITY.—An instrument for measuring the loudness of a signal by comparison with another signal. It consists of a pair of headphones and a variable resistance which have been calibrated.

MHO.—The unit of conductance. As conductance is the reciprocal of resistance it is measured by the reciprocal ohm or mho.

MICA.—A transparent mineral having a high insulating value and which can be split into very thin sheets. It is largely used in making condensers both for transmitting and receiving sets.

MICROFARAD.—The millionth part of a farad.

MICROHENRY.—The millionth part of a farad.

MICROMICROFARAD.—The millionth part of a microfarad.

MICROHM.—The millionth part of an ohm.

MICROPHONE TRANSFORMER.—See Transformer, Microphone.

MICROPHONE TRANSMITTER.—See Transmitter, Microphone.

MILLI-AMMETER.—An ammeter that measures a current by the one-thousandth of an ampere.

MODULATION.—(1) Inflection or varying the voice. (2) Varying the amplitude of oscillations by means of the voice.

MODULATION, BUZZER.—The modulation of radio frequency oscillations by a buzzer which breaks up the sustained oscillations of a transmitter into audio frequency impulses.

MILLIHENRY.—The thousandth part of a henry.

MODULATION, CHOPPER.—The modulation of radio frequency oscillations by a chopper which breaks up the sustained oscillations of a transmitter into audio frequency impulses.

MODULATION, GRID.—The scheme of modulating an oscillator tube by connecting the secondary of a transformer, the primary of which is connected with a battery and a microphone transmitter, in the grid lead.

MODULATION, OVER.—See Blub Blub.

MODULATION, PLATE.—Modulating the oscillations set up by a vacuum tube by varying the current impressed on the plate.

MODULATOR TUBE.—A vacuum tube used as a modulator.

MOTION, WAVE.—(1) The to and fro motion of water at sea. (2) Waves transmitted by, in and through the air, or sound waves. (3) Waves transmitted by, in and through the ether, or electromagnetic waves, or electric waves for short.

MOTOR-GENERATOR.—A motor and a dynamo built to run at the same speed and mounted on a common base, the shafts being coupled together. In wireless it is used for changing commercial direct current into direct current of higher voltages for energizing the plate of a vacuum tube oscillator.

MULTI-STAGE AMPLIFIERS.—See Amplifiers, Multi-Stage.

MUTUAL INDUCTION.—See Induction, Mutual.

MUSH.—Irregular intermediate frequencies set up by arc transmitters which interfere with the fundamental wave lengths.

MUSHY NOTE.—A note that is not clear cut, and hence hard to read, which is received by the heterodyne method when damped waves or modulated continuous waves are being received.

NATIONAL ELECTRIC CODE.—See Code, National Electric.

NATIONAL ELECTRIC SAFETY CODE.—See Code, National Electric Safety.

NEGATIVE ELECTRICITY.—See Electricity, Negative.

NON-SYNCHRONOUS GAP.—See Gap, Non-Synchronous.

OHM.—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.

OHM'S LAW.—The important fixed relation between the electric current, its electromotive force and the resistance of the conductor in which it flows.

OPEN CIRCUIT.—See Circuit, Open.

OPEN CORE TRANSFORMER.—See Transformer, Open Core.

OSCILLATION TRANSFORMER.—See Transformer, Oscillation.

OSCILLATIONS, ELECTRIC.—A current of high frequency that surges through an open or a closed circuit. (1) Electric oscillations may be set up by a spark gap, electric arc or a vacuum tube, when they have not only a high frequency but a high potential, or voltage. (2) When electric waves impinge on an aerial wire they are transformed into electric oscillations of a frequency equal to those which emitted the waves, but since a very small amount of energy is received their potential or voltage is likewise very small.

Sustained.—Oscillations in which the damping factor is small.

Damped.—Oscillations in which the damping factor is large.

Free.—When a condenser discharges through an oscillation circuit, where there is no outside electromotive force acting on it, the oscillations are said to be free.

Forced.—Oscillations that are made to surge in a circuit whose natural period is different from that of the oscillations set up in it.

OSCILLATION TRANSFORMER.—See Transformer.

OSCILLATION VALVE.—See Vacuum Tube.

OSCILLATOR TUBE.—A vacuum tube which is used to produce electric oscillations.

OVER MODULATION.—See Blub Blub.

PANCAKE OSCILLATION TRANSFORMER.—Disk-shaped coils that are used for receiving tuning inductances.

PERMEABILITY, MAGNETIC.—The degree to which a substance can be magnetized. Iron has a greater magnetic permeability than air.

PHASE.—A characteristic aspect or appearance that takes place at the same point or part of a cycle.

PICK-UP CIRCUITS.—See Circuits, Stand-by.

PLATE CIRCUIT REACTOR.—See Reactor, Plate Circuit.

PLATE CURRENT.—See Current, Plate.

PLATE MODULATION.—See Modulation, Plate.

PLATE VOLTAGE.—See Foliage, Plate.

POLES, BATTERY.—The positive and negative terminals of the elements of a battery. On a storage battery these poles are marked + and - respectively.

POLES, MAGNETIC.—The ends of a magnet.

POSITIVE ELECTRICITY.—See Electricity, Positive.

POTENTIAL DIFFERENCE.—The electric pressure between two charged conductors or surfaces.

POTENTIOMETER.—A variable resistance used for subdividing the voltage of a current. A voltage divider.

POWER TRANSFORMER.—See Transformer, Power.

POWER TUBE.—See Generator Tube.

PRIMARY BATTERY.—See Battery, Primary.

PREVENTION, KICK-BACK.—A choke coil placed in the power circuit to prevent the high frequency currents from getting into the transformer and breaking down the insulation.

Q S T.—An abbreviation used in wireless communication for (1) the question "Have you received the general call?" and (2) the notice, "General call to all stations."

QUENCHED GAP.—See Gap, Quenched.

RADIATION.—The emission, or throwing off, of electric waves by an aerial wire system.

RADIO AMMETER.—See Ammeter, Hot Wire.

RADIO FREQUENCY.—See Frequency, Radio.

RADIO FREQUENCY AMPLIFICATION.—See Amplification, Radio Frequency.

RADIO FREQUENCY CURRENT.—See Current, Radio Frequency.

RADIO INSPECTOR.—See Inspector, Radio.

RADIOTRON.—The trade name of vacuum tube detectors, amplifiers, oscillators and modulators made by the Radio Corporation of America.

RADIO WAVES.—See Waves, Radio.

REACTANCE.—When a circuit has inductance and the current changes in value, it is opposed by the voltage induced by the variation of the current.

REACTANCE, CAPACITY.—The capacity reactance is the opposition offered to a current by a capacity. It is measured as a resistance, that is, in ohms.

RECEIVING TUNING COILS.—See Coils, Inductance.

RECEIVER, LOUD SPEAKING.—See Loud Speakers.

RECEIVER, WATCH CASE.—A compact telephone receiver used for wireless reception.

REACTANCE, INDUCTIVE.—The inductive reactance is the opposition offered to the current by an inductance coil. It is measured as a resistance, that is, in ohms.

REACTOR, FILTER.—A reactance coil for smoothing out the pulsating direct currents as they come from the rectifier.

REACTOR, PLATE CIRCUIT.—A reactance coil used in the plate circuit of a wireless telephone to keep the direct current supply at a constant voltage.

RECEIVER.—(1) A telephone receiver. (2) An apparatus for receiving signals, speech or music. (3) Better called a receptor to distinguish it from a telephone receiver.

RECTIFIER.—(1) An apparatus for changing alternating current into pulsating direct current. (2) Specifically in wireless (a) a crystal or vacuum tube detector, and (b) a two-electrode vacuum tube used for changing commercial alternating current into direct current for wireless telephony.

REGENERATIVE AMPLIFICATION.—See Amplification, Regenerative.

RECEPTOR.—A receiving set.

RECEPTOR, AUTODYNE.—A receptor that has a regenerative circuit and the same tube is used as a detector and as a generator of local oscillations.

RECEPTOR, BEAT.—A heterodyne receptor.

RECEPTOR, HETERODYNE.—A receiving set that uses a separate vacuum tube to set up the second series of waves for beat reception.

REGENERATIVE ACTION.—See Feed-Back Action.

REGENERATIVE AMPLIFICATION.—See Amplification, Regenerative.

RELAY, ELECTRON.—A vacuum tube when used as a detector or an amplifier.

REPEATING COIL.—A transformer used in connecting up a wireless receiver with a wire transmitter.

RESISTANCE.—The opposition offered by a wire or other conductor to the passage of a current.

RESISTANCE, AERIAL.—The resistance of the aerial wire to oscillating currents. This is greater than its ordinary ohmic resistance due to the skin effect. See Resistance, High Frequency.

RESISTANCE BOX.—See Resistor.

RESISTANCE COUPLING.—See Coupling, Resistance.

RESISTANCE, HIGH FREQUENCY.—When a high frequency current oscillates on a wire two things take place that are different than when a direct or alternating current flows through it, and these are (1) the current inside of the wire lags behind that of the current on the surface, and (2) the amplitude of the current is largest on the surface and grows smaller as the center of the wire is reached. This uneven distribution of the current is known as the skin effect and it amounts to the same thing as reducing the size of the wire, hence the resistance is increased.

RESISTIVITY.—The resistance of a given length of wire of uniform cross section. The reciprocal of conductivity.

RESISTOR.—A fixed or variable resistance unit or a group of such units. Variable resistors are also called resistance boxes and more often rheostats.

RESONANCE.—(1) Simple resonance of sound is its increase set up by one body by the sympathetic vibration of a second body. (2) By extension the increase in the amplitude of electric oscillations when the circuit in which they surge has a natural period that is the same, or nearly the same, as the period of the first oscillation circuit.

RHEOSTAT.—A variable resistance unit. See Resistor.

RHEOSTAT, CARBON.—A carbon rod, or carbon plates or blocks, when used as variable resistances.

RHEOSTAT, FILAMENT.—A variable resistance used for keeping the current of the storage battery which heats the filament of a vacuum tube at a constant voltage.

ROTATING COIL.—See Coil.

ROTARY GAP.—See Gap.

ROTOR.—The rotating coil of a variometer or a variocoupler.

RUHMKORFF COIL.—See Coil, Induction.

SATURATION.—The maximum plate current that a vacuum tube will take.

SENSITIVE SPOTS.—Spots on detector crystals that are sensitive to the action of electric oscillations.

SHORT WAVES.—See Waves.

SIDE WAVES.—See Wave Length Band.

SIGNALS, CONVENTIONAL.—(1) The International Morse alphabet and numeral code, punctuation marks, and a few important abbreviations used in wireless telegraphy. (2) Dot and dash signals for distress call, invitation to transmit, etc. Now used for all general public service wireless communication.

SKIN EFFECT.—See Resistance, High Frequency.

SOFT TUBE.—A vacuum tube in which the vacuum is low, that is, it is not highly exhausted.

SPACE CHARGE EFFECT.—The electric field intensity due to the pressure of the negative electrons in the space between the filament and plate which at last equals and neutralizes that due to the positive potential of the plate so that there is no force acting on the electrons near the filament.

SPARK.—See Discharge.

SPARK COIL.—See Coil, Induction.

SPARK DISCHARGE.—See Spark, Electric.

SPARK FREQUENCY.—See Frequency, Spark.

SPARK GAP.—(1) A spark gap, without the hyphen, means the apparatus in which sparks take place; it is also called a spark discharger. (2) Spark-gap, with the hyphen, means the air-gap between the opposed faces of the electrodes in which sparks are produced.

Plain.—A spark gap with fixed electrodes.

Rotary.—A spark gap with a pair of fixed electrodes and a number of electrodes mounted on a rotating element.

Quenched.—A spark gap formed of a number of metal plates placed closely together and insulated from each other.

SPIDER WEB INDUCTANCE COIL.—See Coil, Spider Web Inductance.

SPREADER.—A stick of wood, or spar, that holds the wires of the aerial apart.

STAGGER WOUND COILS.—See Coils, Inductance.

STAND-BY CIRCUITS.—See Circuits, Stand-By.

STATIC.—Also called atmospherics, grinders, strays, X's, and, when bad enough, by other names. It is an electrical disturbance in the atmosphere which makes noises in the telephone receiver.

STATOR.—The fixed or stationary coil of a variometer or a variocoupler.

STORAGE BATTERY.—See Battery, Storage.

STRAY ELIMINATION.—A method for increasing the strength of the signals as against the strength of the strays. See Static.

STRAYS.—See Static.

STRANDED WIRE.—See Wire, Stranded.

SUPER-HETERODYNE RECEPTOR.—See Heterodyne, Super.

SWINGING.—See Fading.

SWITCH, AERIAL.—A switch used to change over from the sending to the receiving set, and the other way about, and connect them with the aerial.

SWITCH, LIGHTNING.—The switch that connects the aerial with the outside ground when the apparatus is not in use.

SYMBOLS, APPARATUS.—Also called conventional symbols. These are diagrammatic lines representing various parts of apparatus so that when a wiring diagram of a transmitter or a receptor is to be made it is only necessary to connect them together. They are easy to make and easy to read. See Page 307 [Appendix: Symbols Used for Apparatus].

SYNCHRONOUS GAP.—See Gap, Synchronous.

TELEPHONY, LINE RADIO.—See Wired Wireless.

THERMAL AMMETER.—See Ammeter, Hot Wire.

THREE ELECTRODE VACUUM TUBE.—See Vacuum Tube, Three Electrode.

TIKKER.—A slipping contact device that breaks up the sustained oscillations at the receiving end into groups so that the signals can be heard in the head phones. The device usually consists of a fine steel or gold wire slipping in the smooth groove of a rotating brass wheel.

TRANSFORMER.—A primary and a secondary coil for stepping up or down a primary alternating or oscillating current.