Glossary of Wireless Terms

Radio Record, Volume II, Issue 13, 12 October 1928, Page 28

Glossary of Wireless Terms

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

RECTIFICATION. — The high-fre-quency energy received on the aerial must be reduced to within the range of audibility before it can influence the telephones, and this function is carried out by either a valve or crystal detector which which, by choking back each positive half-cycle of high-frequency oscillation and permitting only the remaining negative half-cycle to pass reduces highfrequency ostillation to low-frequency undirectional impulse. For charging accumulators it is necessary to convert alternating current into direct or impulsive current, and this is done by a rectifier by cutting off those impulses of current flowing in the wrong direction. RECTIFIER. — See "Rectification" ; see also "Detector Valve," "Bulb Rectifier," "Blectrolytic Rectifier," "Oxide Rectifier."’ REFLEX.-Type of circuit in which amplification is repeated through one or more valves. Thus a valve may perform the duty of an amplifier of radio as well as audio-frequencies simultaneously. This is also known as dual amplification. See "Dual." . RELAY.-A piece of apparatus operated by a feeble current employed to im‘port into the circuit a heavier local current, which latter is capable of performing the service for which the original current is too feeble. The valve is a species of relay, and in the early days of its development was called an "electron relay" ~-a particularly apt term. REGENERATION.-See "Reaction." RESIDUAL CAPACITY.-Refers to the small amount of capacity remaining between the fixed and moxing vanes of a variable’ condenser when they are at minimum position.

RESISTANCE.-Measured in Ohms (see "Ohm’s Law’), and refers to the opposition encountered by electricity in flowing through 4 conductor. RESISTANCE CAPACITY AMPLI-CATION.-A. system of either radio or audio frequency amplification whether two valves are coupled together with a resistance, condenser, or grid leak. Such amplification is relatively insensitive compared to transformer systems, and although credited with distortionless results has to be carefully arranged -so far as values and valves are concerned to achieve this. RESONANCE.-If two tuned circuits fare both adjusted to the same waveleigth they are said to be in resonance or resonant to one another. An aerial tuned to 400 metres will be resonant or respond to a station transmitting on that wavelength. RHEOSTAT.-A variable resistancy ' wsed for the purpose of controlling the

heat of valve filaments. It is connected in series with the A battery. ROTOR.-Moving or rotating elements of a variometer or yario-coupler. The rotor plates of a condenser are those which move. SECONDARY.-See "Primary Battery’; also "Primary." SELECTIVITY.-See- "Sharp Tun ing." SELF-CAPACITY.-Refers to the capacity natural to a design of unit such as a choke or inductance coil, for instance. A condenser effect is always apparent between turns, and to keep: this undesirable element at a minimum special methods of winding are resorted to. See ‘Honeycomb or Basket Windings." A coil may exhibit large self-capacity because of the close proximity of metal. SELF HETERODYNE.-Instead of using a seperate apparatus for the generatign of local oscillations for the reception of continuous wave telegraphy, the receiving valve itself may be made to oscillate and so render reception of the "beat-note" possible. SENSITIVITY.-A _highly-desirable quality in all receiving sets; mainly dependent upon efficient design and construction; applies also to telephone receivers, and valves or crystals. SERIES.-Parallel connection. See "Parallel."

SERIES-PARALLEL SWITCH.A double-pole, double-throw switch, used to change the connection of the aerial tuning condenser from series to parallel or the reverse. SHARP-TUNING.-With an efficient set it should be possible to tune out even powerful stations within a few. degrees on either side of the "optimum" condenser setting. Difficulty in tuning out the loeal station is usually due to a lack of sensitivity-that is, inability to tune @gharply-in the receiver. SHIELDING.-In order to retain a certain degree of compactness in a receiying set it is often necessary to place certain components closer together than is theoretically desirable, and in order to minimise possible interaction, the components (such as low-frequency transformers) are shrouded with soft iron, lead, tin foil, or copper foil. SHORT-WAVE.-Prior to broadcasting, the wavelength now used for this purpose would have been regarded as short, but now in speaking of short waves something of the order of 15 to 200 metres is meant. SHROUDING.-See "Shielding." PPVTTTTTITITiTiTirirrrrrirrrrrirririirty | POUT UTELILELTEL LETTE? ELIE ALT IEL IL AIT AL IL ALL ALAALLAALEAAEBALALALAL ALLA |