Review Questions and Answers

What is meant by an "A" powei supply?

Ans. A power supply device providing heating current for the cathode of a vacuum tube.

What is an alternating current?

Ans. A current, the direction of which reverses at regularly recurring intervals, the algebraic average value being zero.

What is meant by amplification factor?

Ans. A measure of the effectiveness of the grid voltage relative to that of the plate voltage in affecting the plate current.

Describe an amplifier.

Ans. A device for increasing the amplitude of electric current, voltage or power, through the control by the input power of a larger amount of power supplied by a local source to the output circuit.

What is an anode?

Ans. An electrode to which an electron stream flows.

What is an antenna?

Ans. A conductor or a system of conductors for radiating or receiving radio waves.

What is meant by the term atmospherics? Ans. Strays produced by atmospheric conditions.

Describe what is meant by attenuation.

Ans. The reduction in power of a wave or a current with increasing distance from the source of transmission.

What is the approximate length of audio frequency waves?

Ans. A frequency corresponding to a normally audible sound wave. The upper limit ordinarily lies between 10,000 and 20,000 cycles per second.

What is an audio frequency transformer? Ans. A transformer for use with audio frequency currents.

What is meant by autodyne reception?

Ans. A system of heterodyne reception through the use of a device which is both an oscillator and a detector.

Describe an automatic volume control device.

Ans. A self-acting device which maintains the output constant within relatively narrow limits while the input voltage varies over a wide range.

What is meant by a "B" power supply?

Ans. A power supply connected in the plate circuit of a vacuum tube.

Describe and give the function of a "Baffle."

Ans. A partition which may be used with an acoustic radiator to impede circulation between front and back.

Describe a band-pass filter.

Ans. A filter designed to pass currents of frequencies within a continuous band limited by an upper and a lower critical or cut-off frequency and substantially reduce the amplitude of currents of all frequencies outside of that band.

What is meant by the term "Beat"?

Ans. A complete cycle of pulsations in the phenomenon of beating.

What is meant by beat-frequency?

Ans. The number of beats per second. This frequency is equal to the difference between the frequencies of the combining waves.

What is meant by the term beating?

Ans. A phenomenon in which two or more periodic quantities of different frequencies react to produce a resultant having pulsations of amplitude.

What is meant by broadcasting?

Ans. Radio transmission intended for general reception.

Describe a by-pass condenser.

Ans. A condenser used to provide an alternating current path of comparatively low impedance around some circuit element.

What is meant by a "C" power supply?

Ans. A power supply device connected in the circuit between the cathode and grid of a vacuum tube so as to apply a grid bias.

What is meant by a capacity coupling?

Ans. The association of one circuit with another by means Of capacity common or mutual to both.

Describe a carbon microphone.

Ans. A microphone which depends for its operation upon the variation in resistance of carbon contacts.

Describe the meaning of the term carrier.

Ans. A term broadly used to designate carrier wave, carrier current or carrier voltage.

What is meant by carrier frequency? Ans. The frequency of a carrier wave.

What is meant by carrier-suppression?

Ans. That method of operation in which the carrier wave is not transmitted.

What is a carrier wave?

Ans. A wave which is modulated by a signal and which enables the signal to be transmitted through a specific physical system.

What is a cathode? Ans. The electrode from which the electron stream flows.

Describe and give the function of a choke coil.

Ans. An inductor inserted in a circuit to offer relatively large impedance to alternating current.

Describe a condenser loud speaker.

Ans. A loud speaker in which the mechanical forces result from electrostatic reactions.

Describe a condenser microphone.

Ans. A microphone which depends for its operation upon variations in capacitance.

What is meant by continuous waves?

Ans. Continuous waves are waves in which successive cycles are identical under steady state conditions.

Define the meaning of Conversion transconductance.

Ans. The ratio of the magnitude of a single beat-frequency component (fi+f2) or (fi —f2) of the output current "to the magnitude of the input voltage of frequency fi under the conditions that all direct voltages and the magnitude of the second input alternating voltage f2 must remain constant. As most precisely used, it refers to an infinitesimal magnitude of the voltage of frequency fi.

Describe a converter generally as applied to super-heterodyne receivers.

Ans. A converter is a vacuum tube which performs simultaneously the functions of oscillation and mixing (first detection) in a radio receiver.

What is meant by coupling?

Ans. The association of two circuits in such a way that energy may be transferred from one to the other.

What is meant by cross modulation?

Ans. A type of intermodulation due to modulation of the carrier of the desired signal in a radio apparatus by an unde-sired signal.

What is meant by current amplification?

Ans. The ratio of the alternating current produced in the output circuit of an amplifier to the alternating current supplied to the input circuit for specific circuit conditions.

What is a cycle?

Ans. One complete set of the recurrent values of periodic phenomenon.

What are damped waves?

Ans. Waves of which the amplitude of successive cycles at the source, progressively diminishes.

What is a decibel?

Ans. The common transmission unit of the decimal system» equal to 1/10bel.

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What is meant by detection?

Ans. Any process of operation on a modulated signal waves to obtain the signal imparted to it in the modulation process/

What is a detector?

Ans. A device which is used for operation on a signal wave to obtain the signal imparted to it in the modulation process.

Describe a diode vacuum tube.

Ans. A type of thermionic tube containing two electrodes which passes current wholly or predominantly in one direction.

What is meant by direct capacitance (C) between two conductors?

Ans. The ratio of the charge produced on one conductor by the voltage between it and the other conductor divided by this voltage, all other conductors in the neighborhood being at the potential of the first conductor.

What is meant by direct coupling?

Ans. The association of two circuits by having an inductor, a condenser, or a resistor common to both circuits.

What is a direct current?

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