Glossary of Wireless Terms

Radio Record, Volume II, Issue 6, 24 August 1928, Page 29

Glossary of Wireless Terms

From week to week we give here asection of the glossary of wireless terms trom the "Listener’s Guide." ;

HIGH FREQUENCY RESISTANCE. -The resistance which a conducting path offers to high-frequency currents. Skin effect renders this higher than the resistance that would be offered by the same path to a continuous or low-frequency current, Skin effect refers to the property of H.F. currents of flowing on the outer edges of a conductor and not penetrating to the core. The higher the frequency the less the penetration. HIGH-TENSION (H.T.) OR "B" BATTERY.-The battery which supplies the current flowing from the plate to the filament in a radio valve. See B battery. HONEYCOMB COIL.-A type of multilayer coil in which the lattice formation of the successive layers suggests the honeycomb. See "Duo-lateral Coil." HOOK-UP. An Americanism for "circuit." _ HOT-WIRE AMMETER.- An _ instrument used in radio transmission work which measures current in amperes by means of a wire. expanding in proportion to the heat generated by the passing current. As the wire alters in length it pulls a2 pointer round a graduated scale against a spring. This type of meter will read either direct, alternating, or oscillating currents, with average accuracy. If specially calibrated for one type of current or frequency, it is quite accurate. General abbreviation, "H.W.A." HYGROSCOPIC.-Susceptible to the accumulation of moisture, such as condensation from the breath. . IMPEDANCE.-The total opposition offered by a circuit, or piece of apparatus, to a varying or alternating current, being made up of the combined effects of resistance and reactance. See "Inductance." ~ IMPULSIVE CURRENT.-A current flows in a given direction, but varies in quantity at either a radio or an audio-frequency. Such a current flows _ from the B battery of a radio set. . INDEPENDENT HETERODYNE.A separate apparatus solely to generate local oscillatons for the reception of continuous wave telegraphy. See ‘"‘Heterodyne."

INDOOR AERIAL.-Considerable efficiency can be obtained with a well-de-signed, well-insulated, indoor aerial and a standard earth, and it is much to be preferred to a frame for normal reception if a full-sized outdoor aerial is not possable. INDUCTANCE.-When an oscillating or alternating current is passed through a coil of wire, opposition is offered to its flow by virtue of the magnetic effect of the current. This opposition is measured in terms of impedance, and the two factors determining impedance are inductance and resistance. Resistance has been explained elsewhere. The inductance (or self-inductance as it is generally called) becomes the greater, the larger the number of turns or the greater the diameter of the turns. If an iron cone is introduced into the winding, the inductance increases hundreds of times in value, because of the increased magnetic effect. In actual terms of measurement, selfinductance is known as "re-actance." INDUCTION.-The production of an electromotive force in an electric circuit through the agency of another circuit, without any direct electrical connection between the two. Induction may be brought about by lines of electric force (electro-static magnetic induction). Upon the latter depends the working of the ransformer, certain tuning coils, and the loose coupler. INDUCTION COIL.-A piece of apparatus for producing high-voltage or -practically-speaking unidirectional currents from a low voltage direct current supply. It is largely used for producing the snark discharge on ships’ "emergency" transmitting sets and small land spark stations. INTERACTION.-May be deliberate or accidental. Ordinary reaction is in-ter-action, and if carefully used is beneficial. In a badly-designed set, or with badly-designed parts, there may be interaction between two low-frequency transformers, between two coils which should be isolated or even between actual leads in the wiring, which are not sufficiently widely separated.