COUNTER EMFThe voltage generated within a coil by a moving magnetic field cutting across the coil
itself. This voltage is in opposition (counter) to the moving field that created it. Counter emf is present
in every motor, generator, transformer, or other inductance winding whenever an alternating current
flows  .
COUNTERPOISEA network of wire connected to a quarter-wave antenna at one end. The network
provides the equivalent of an additional one-fourth wavelength .
COUPLINGThe process of transferring energy from one point in a circuit to another point, or from one
circuit to another .
COUPLING CAPACITORA capacitor used to couple signals .
COUPLING DEVICEA coupling coil that connects the transmitter to the feeder .
COVALENT BONDA type of linkage between atoms in which the atoms share valence electrons .
CPRCardiopulmonary Resuscitation .
CREST (TOP)The peak of the positive alternation (maximum value above the line) of a wave .
CRITICAL ANGLEThe maximum angle at which radio waves can be transmitted and still be refracted
back to earth .
CRITICAL FREQUENCYThe maximum frequency at which a radio wave can be transmitted vertically
and still be refracted back to earth .
CROSSED-FIELD AMPLIFIERA high-power electron tube that converts dc to microwave power by a
combination of crossed electric and magnetic fields .
CROSS-SECTIONAL AREAThe area of a "slice" of an object. When applied to electrical conductors it
is usually expressed in circular mils .
CROWN-OF-THORNS TUNERSee SPROCKET TUNER .
CRYSTALA natural substance, such as quartz or tourmaline, that is capable of producing a voltage when
under physical stress or of producing physical movement when a voltage is applied .
CRYSTAL FURNACEA device for artificially growing cylindrical crystals to be used in the production
of semiconductor substrates .
CRYSTAL MICROPHONEA microphone that uses the piezoelectric effect of crystalline matter to
generate a voltage from sound waves .
CRYSTAL OVENA closed oven maintained at a constant temperature in which a crystal and its holder
are enclosed to reduce frequency drift .
CURRENTThe movement of electrons past a reference point. The passage of electrons through a
conductor. Measured in amperes .
CURRENT-FEED METHODSame as CENTER-FEED METHOD .
CURRENT RATINGThe safe current-carrying capacity of a wire or cable on a continuous basis .
CURRENT REGULATORA circuit that provides a constant current output .