Glossary of Wireless Terms

Radio Record, Volume I, Issue 47, 8 June 1928, Page 14

Glossary of Wireless Terms

UNDER this heading we will give regularly sections of the glossary of wireless terms which is a prominent feature of the N.Z. Radio Listeners’ Guide. In that book, although set in the smallest type, it occupies some 13 pages, and is definitely in our opinion the most comprehensve and complete glossary on modern lines which has been made available in the Dominion. For the benefit of our ' readers the glossary will be reprinted in our columns.

AERIAL, LOOP OR FRAME.-This type of aerial is wound on a frame which may rotate or orientate. An "earth" connection is not necessary when a loop or frame aerial is used, although in some cases it ean be added with advantage. Its chief advantages are portability and freedom from "jamming" or interference by reason of the fact that it is more sensitive in receiving signals from the direction in which it is pointed, although, for instance, if it were pointed north and south it would receive equally well from both directions, while signals coming from east and west would be weak or inaudible. A good loop, or frame, acrial is only about one-twentieth as efficient as a good outdoor aerial. AERIAL TUNING INDUCTANCE (A.T.1.).-The variable inductance, or tuning coil, in circuit with the aerial, which enables the wavelength of the aerial, circuit to be altered or tuned. The greater the wavelength desired, the greater must be the portion of the A.T.I, included in the cireuit.

AIR GAP.-Describes the space between the magnet pole faces and the diaphragm in telephones or loudspeakers. Careful adjustment of this air gap often results in a considerable improvement in both signal strength and quality. May also refer to the gap existing between the clectrodes or points across which discharges take place in lightning arrester. | ALTERNATING CURRENT.-The -house-lighting system most commonly used in New Zealand. It derives its ‘name from the fact that its direction alternates so many times per second. | The standard in New Zealand is 50, but the old Wellington system employed 80. The current builds in one direction from zero, and haying obtained a maximum, falls to zero and then reverses in direction, building to a maximum and again reduces to zero. Such an impulse with its reversal is known as a cycle. Hence standard alternating current in New Zealand is said to be of a frequency of 50 cycles per second, AMMETER.-An ampere meter, or instrument for measuring in amperes the current flowing in an electric circuit. AMPERE.-The standard unit of electric current, being the current that can be driven through a resistance of one ohm by a pressure of oné volt. If the terminals of a single 2-volt accumulator cell are joined by 14 yards of No. 28 S.W.G. copper wire, a current of one ampere will flow in the wire; or in other words, the resistance of such 2 wire is 2 ohms. AMPLIFIER.-May be applied to a valve or valves, or a combination of valyes coupled together for the purpose of amplifying or magnifying electrical effects. Amplifiers may be either "radio" ("high") frequency, or "audio" ("low") frequency. The former magnifies the electrical impulses before they reach the detector valve (or crystal), | and the "audio" amplifier magnifies the output from the detector, H.I".; High-

frequently, or radio amplifier. L.F.t Low-frequency, or audio, amplifier. ANODE.-The electrode or terminal of the output circuit of a valve. It is commonly known as the "plate" of a valye. The "B" battery positive (or "plus") terminal is always connected to the anode. The term "anode" is most frequently used in contra-distinction to "kathode". wherever two electrodes are used as in a battery or other electrical device. The anode is always the positive and the kathode the negative. ANTENNA,.-Another term for "serial." It is generally used in the Ameriean parlance. APERIODIC.-A circuit so heavily damped as to be responsive to a wide band of frequencies and to have no sharply defined peak or optimum point, is said to be aperiodic.

ARC-The passage of electricity through air or gas in the form of an intensely hot and visible discharge, con sisting of vaporised particles of the electrodes between which the discharge takes place, ARMSTRONG CIRCUIT.-A super regenerative circuit capable of remark-~ able results in experienced hands. Consists essentially of a reaction coil, either tuned or untuned, placed in the plate circuit of the detector valve and coupled back to the grid circuit. This wellknown principle is known under other names in other countries where it was separately discovered. Armstrong is the American name, : ATMOSPHERICS.-Generally applied to the atmospheric electrical discharges also termed "static." When intense, serious intereference with radio reception is occasioned, especially as_ there is no definite wave-length. So far no device has yet been invented which is of a form suitable for use by the general body of listeners to reduce interference ‘by atmospherics without proportionately reducing signal strength other than by the use of a loop aerial and this is of questionable value in many instances, AUDIO FREQUENCIES.-AI _ frequencies corresponding to _ vibrations audible to the human ear. Frequencies less than 10,000 cycles per second are ‘termed "audo frequencies." The fre- quency of the sound waves produced ‘by the middle C on the piano is 256. A frequency of 1000 per second corres~ ponds to the sing of the mosquito. The ‘upper frequencies approaching 10,000 therefore correspond to the overtones which characterise a banjo as distinct from a piano for instance. AUDION.-The name first given in the UWinted States to the radio valve of the three-electrode type now commonly in use. Originally a trade name it was adopted into common parlance all over the Wnglish-speaking world until about 1928, when the word "tube" was adopted in North America and "valve". in Britain and the other Dominions.