effect of iron core upon, 207;
matching of, 196

Intermediate-frequency amplification, 242

Inductance, defined, 83;
effect upon frequency, 100;
impedance of, 135;
mutual, 109;
of coils, 101;
self, 83;
table of values, 227;
unit of, 83;
variable, 108

Induction, principle of, 208

Inducto-meter, 109

Input circuit, 187

Interference, 249

Internal resistance, 191

Ion, definition of, 19;
positive and negative, 20, 21

Ionization, 20

Larynx, 153

Laws of attraction, 204

Loading coil, 224

Loop antenna, 198

Magnet, pole of, 203;
of soft iron, 205;
of steel, 205

Magnetism, 202

Matter, constitution of, 5

Megohm, 172

Microfarad, 104

Mil-ampere, 71

Mil-henry, 83

Modulation, 145, 230, 237, 239

Molecule, kinds of, 6;
motion of, 35

[Greek: mu], 190

Multiplex telegraphy, 258;
telephony, 258

Mutual inductance, 109;
variation of, 110

Natural frequency, 161

Nitrogen, 10

Nucleus of atom, 10, 12

Ohm, defined, 64

Organ pipe, 160

Oscillations, 87;
damped, 114;
to start, 114;
intensity of, 236;
natural frequency of, 117

Output circuit, 187

Overtones, 159

Oxygen, percentage in air, 10

Phase, 180

Plate, of an audion, 41

Plunger type of instrument, 205

Polarity of a coil, 204

Power, defined, 234;
electrical unit of, 235

Proton, properties of, 4

Radio current, modulation of, 145

Radio-frequency amplification, 243;
limitations, 243

Radio-frequency amplifier, 186, 198

Radio station connected to land line, 254

Rating of tubes, 235

Reception, essential operations in, 235

Regenerative circuit, 176;
frequency of, 179

Repeater stations, 261

Resistance, measurement of, 64;
non-inductive, 103;
square, 251

Resonance, 161

Resonance curve, 117

Retard coils, 210

Salt, atomic construction of, 17;
crystal structure, 147;
molecule in solution, 19;
percentage in sea water, 11

Saturation, 38

Sea water, atomic constitution of, 11

Self-inductance, 83;
unit of, 83

Side bands, 248;
relation to wave lengths, 249