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the maintenance of the coordinated variation of the resonant frequencies of oscillatory circuits of, for example, a superheterodyne receiver, that are tuned by means of a single control knob. When a superheterodyne receiver is tuned to a certain signal, the resonant frequency frad of the input circuit and the radio-frequency amplifier is set equal to the frequency fsig of the received signal, and the resonant frequency fosc of the local oscillator is adjusted so that the intermediate frequency (usually equal to the difference between frad and fosc) coincides with the resonant frequency of the intermediate-frequency amplifier.
Tracking is generally accomplished by employing identical variable capacitors in all tunable circuits and by using additional fixed capacitors, called padders, in the local oscillator circuit, which must have a frequency different from frad (see Figure 1). In this case, the relations between the angle of rotation of the tuning knob and frad and between the angle of rotation and fosc are not exactly those required—that is, the tracking is only approximate. Nonetheless, the tracking is still sufficiently accurate. In the receivers of the mid-1970’s, the variable capacitors used are either capacitors with mechanically varied capacitance or varactors (varicaps).
REFERENCESRadiopriemnye ustroistva. Edited by V. I. Siforov. Moscow, 1974.
Chistiakov, N. I., and V. M. Sidorov. Radiopriemnye ustroistva. Moscow, 1974.
V. M. SIDOROV
ii. A motion given to the major lobe of an antenna so that a preassigned moving target in space remains in the lobe's field as long as it is within viewing range.
iii. The process of determining the position of the tips of the propeller blades relative to one another. See blade track and tracking flag.
iv. The mechanical procedure used to bring the blades of the rotor into satisfactory relationship with one another under dynamic conditions, so that all blades rotate in a common plane. See blade track.
Tracking should not be confused with kerning which deals with the spacing between certain pairs of characters.
See also leading.
tracking(1) See Bluetooth tracker, vehicle tracking and child tracking.
(2) The recording of an event. See tracking cookie and email tracker.
(3) Synchronizing a reading or writing mechanism with a rotating platter. For example, a stylus must maintain a smooth contact with the groove in a vinyl phonograph record. A laser must align itself precisely to the tracks of a CD.
(4) In desktop publishing, the consistent letterspacing of text. Tracking is used to expand or contract the amount of text on a page by expanding or reducing the amount of space between letters. It differs from kerning in that it is applied to an entire font or to a range of text, whereas kerning refers to certain letter pairs.