18WuD2x

tuned-collector oscillator • tunnel-diode amplifier 697
tuned-collector oscillator A self-excited, common-emitter
connected, bipolar-transistor oscillator
in which the tuned tank is in the collector
circuit.
C1
R1
R2
R3
C3
C2
tuned-collector oscillator
−
+
T
V CC
Output
tuned coupler An antenna coupler (transmatch)
that can be adjusted independently of the transmitter
or receiver with which it is used.
tuned dipole A half-wave, center-fed, resonant antenna.
tuned feeders An antenna feed line that is adjusted
or trimmed so that the entire system (feeders
and radiating element) is resonant at the
transmitted-signal frequency.
tuned headphones Headphones used in radio-telegraphy
that are fix-tuned to a single audio frequency
(e.g., 1 kHz) by means of a small parallel capacitor.
tuned line An antenna wire or transmission line
that provides a resistive load at a specific resonant
frequency.
tuned pickup A pickup circuit or device (such as a
radio-frequency sampling coil) that is tuned to
the signal frequency.
tuned radio-frequency amplifier An amplifier circuit
that is continuously tunable over a specific
band of radio frequencies.
tuned radio-frequency receiver A radio receiver
consisting only of a tuned-radio-frequency amplifier,
detector, and audio amplifier. Compare SU-
PERHETERODYNE RECEIVER.
tuned reed A vibrating reed whose length, width,
and/or thickness have been adjusted so that it
vibrates naturally at a desired frequency.
tuned-reed frequency meter An audio frequency
meter using tuned metal reeds as the indicators.
Also see POWER FREQUENCY METER, 2.
tuned relay An electronic or electromechanical relay
that closes at one frequency. See, for example,
REED SWITCH, 1.
tuned signal tracer A signal tracer that can be
tuned sharply to the frequency of the test signal
being traced.
tuned transformer An audio-frequency or radiofrequency
transformer tuned via a capacitor in
parallel with its primary winding and/or a capacitor
in parallel with it secondary winding.
tuner A circuit or device that can be set to select
one signal from a number of signals in a frequency
band.
tungsten Symbol, W. A metallic element. Atomic
number, 74. Atomic weight, 183.85. Also called
wolfram. It is used in switch and relay contacts,
in the elements of some electron tubes, and in incandescent-lamp
filaments.
tuning 1. Adjustment of the frequency of a receiver
to intercept a signal on a given frequency. 2. Adjustment
of a transmitter oscillator to a desired
frequency. 3. Adjustment of an inductancecapacitance
circuit for resonance on a desired
frequency. 4. Adjustment of an antenna or
antenna system to a desired frequency. 5. Adjustment
of a radio-frequency amplifier for optimum
performance. 6. Alignment of a musical instrument
for correct tone frequency.
tuning capacitor A variable capacitor used to tune
an inductance-capacitance circuit (seriesresonant
or parallel-resonant).
tuning coil A variable inductor used to tune an inductance-capacitance
circuit (series-resonant or
parallel-resonant).
tuning core See TUNING SLUG.
tuning diode See VOLTAGE-VARIABLE CAPACI-
TOR, 1.
tuning fork A metal device that vibrates at a precise
audio frequency when struck physically. It
usually has two prongs and looks something like
a fork.
tuning-fork oscillator See FORK OSCILLATOR.
tuning indicator 1. A meter or display that indicates
when a receiver is properly tuned to the frequency
of an incoming signal. 2. Sometimes, a
bridge null detector.
tuning meter A meter-type resonance indicator.
tuning potentiometer A single or ganged potentiometer
(depending on the circuit in which it is
used) used to vary the frequency response of a
resistance-capacitance-tuned circuit, such as
the bridge-tee, parallel-tee or Wien-bridge
circuit.
tuning slug A powdered-iron core that slides or
screws in and out of a coil to vary the inductance.
tuning voltage An adjustable direct-current voltage
used to vary the capacitance of a varactor
diode (serving as the capacitor in a tuned circuit).
tuning wand See NEUTRALIZING TOOL.
tunnel diode A specially processed junction diode
whose forward conduction characteristic displays
negative resistance.
tunnel-diode amplifier A circuit that uses the
negative-resistance properties of a tunnel diode