Page 76 - The Illustrated Dictionary of Electronics

5059F-pB_56-92 4/9/01 4:45 PM Page 61

balun • bandstop 61

usually providing a 1:1 or 1:4 impedance ratio against all frequencies except a specific frequency
and available in several different forms. It is so f 0, or a band of frequencies between two limiting
called because it has an unbalanced input suit- frequencies f 0 and f 1. In a parallel inductance-
able for coaxial transmission lines, and a bal- capacitance (LC) circuit, the device exhibits high
anced output suitable for dipole, Yagi, and quad impedance at the desired frequency or frequen-
antennas. cies and a low impedance at unwanted frequen-
banana jack The female half of a two-part quick- cies. In a series configuration, the filter has a low
connector combination. Splicing of a circuit is impedance at the desired frequency or frequen-
completed by inserting a BANANA PLUG into this cies and a high impedance at unwanted freque-
jack. ncies. Compare BAND-REJECTION FILTER,
banana plug The male half of a two-part quick- HIGH-PASS FILTER, LOW-PASS FILTER.
connector combination, with sides usually com- bandpass flatness The degree to which a bandpass
posed of flat springs that ensure contact with the device’s attenuation-versus-frequency curve is a
female BANANA JACK into which it is inserted. straight line with zero slope within the passband.
band pressure level The net acoustic pressure of a
sound source within a specified frequency range
(band).
band-rejection filter Also called a band-stop filter.
Any resonant circuit, or combination of resonant
circuits designed to discriminate against a spe-
cific frequency f 0, or a band of frequencies be-
banana jack and plug tween two limiting frequencies f 0 and f 1. In a
parallel inductance-capacitance (LC) circuit, the
device exhibits high impedance at the desired fre-
band 1. A continuous range of radio or television quencies, and a low impedance at the unwanted
communications frequencies or wavelengths, frequency or range of frequencies. In a series con-
usually designated by the lowest and highest fre- figuration, the filter has a low impedance at the
quencies, or the approximate wavelength (e.g., desired frequencies and a high impedance at the
the 20-meter amateur radio band). 2. A set of dis- unwanted frequency or range of frequencies.
crete radio or television frequency channels Compare BANDPASS FILTER, HIGH-PASS FIL-
within a specified range (e.g., the standard AM TER, LOW-PASS FILTER, NOTCH FILTER.
broadcast band). 3. A range of wavelengths for in- band selector Any switch or relay that facilitates
frared, visible, ultraviolet, X-ray, or gamma-ray switching the frequency of a radio transmitter, re-
energy. 4. A range of energy levels. 5. A colored ceiver, or transceiver among various bands.
stripe on a resistor or capacitor that forms part of bandset capacitor In some older communications
the code that indicates component value and tol- receivers, a variable capacitor is used to preset
erance. the tuning range in each band to correspond to
band center 1. In a given radio or television com- graduations on the tuning dial. This capacitor is
munications band, the arithmetic mean of the a trimmer or padder operated in conjunction with
lowest and highest frequencies. 2. In a given the main tuning capacitor.
band, the geometric mean of the longest and bandspreading In some older communications re-
shortest wavelengths. ceivers, the process of widening the tuning range
band-elimination filter See BAND-REJECTION within a given frequency band to cover the entire
FILTER. dial. Otherwise, the band would occupy only a
band gap In any atom, the difference in electron en- portion of the dial, and tuning would be difficult.
ergy between the conduction and valence bands. It is usually accomplished with a BANDSPREAD
bandpass 1. The frequency limits between which a TUNING CONTROL whose range is preset via the
BANDPASS FILTER or BANDPASS AMPLIFIER main tuning control and/or a BANDSET CAPAC-
transmits ac energy with negligible loss. 2. The ITOR.
ability to allow passage of signals at a given fre- bandspread tuning control An analog adjustment
quency or band of frequencies while blocking in some older communications receivers that al-
other signals. Compare BANDSTOP. lows continuous tuning over a desired band of
bandpass amplifier An amplifier that is tuned to frequencies. This control is separate from the
pass only those frequencies between preset limits. main tuning control.
bandpass coupling A coupling circuit with a flat- bandstop 1. The frequency limits between which a
topped frequency response so that a band of fre- BAND-REJECTION FILTER blocks, or greatly
quencies, rather than a single frequency, is attenuates, ac energy. 2. The ability to suppress
coupled into a succeeding circuit. Also see BAND- or block signals of a given frequency or band
PASS, 1. of frequencies, while allowing signals of other
bandpass filter Any resonant circuit, or combina- frequencies to pass with little or no attenuation.
tion of resonant circuits, designed to discriminate Compare BANDPASS.