SPHERICAL WAVEFRONTSWaves of energy that spread out in concentric circles .
SPLATTERUnwanted sideband frequencies that are generated from overmodulation .
SPLICEA joint formed by the connecting of two or more conductors .
SPORADIC E LAYERIrregular, cloud-like patches of unusually high ionization. Often forms at heights
near the normal E layer .
SPREADERInsulator used with transmission lines and antennas to keep the parallel wires separated .
SPROCKET TUNERA mechanical tuning device for magnetron tubes that changes the frequency of the
cavities by changing the inductance. Also called a CROWN-OF-THORNS TUNER .
SQUARE MILThe area of a square, the sides of which are each equal to 1 mil. One square mil is equal to
1.2732 circular mils .
SQUELCHA circuit that cuts off the output of a receiver when there is no input .
SQUIRREL-CAGE WINDINGSA type of rotor winding in which heavy conductors are imbedded in the
rotor body. The conductors are shorted together at the ends by continuous rings. It is widely applied in
ac induction motors. Physically, it appears as a rotating squirrel-cage, thus the name .
STABILITYIn a magnetron, the ability to maintain normal operating characteristics .
STAGEOne of a series of circuits within a single device; for example, first stage of amplification .
STAGGER TUNINGA method of klystron tuning in which the resonant cavities are tuned to slightly
different frequencies to increase the bandwidth of the amplifier .
STANDING WAVEThe distribution of voltage and current, formed by the incident and reflected waves,
that has minimum and maximum points on a resultant wave that appear to stand still .
STANDING-WAVE RATIO (SWR)The ratio of the maximum (voltage, current) to the minimum
(voltage, current) points of a transmission line. Indicates the impedance matching quality of the
termination of the line  .
STARTThe first unit of a teletypewriter signal. It is always a space .
STATIC(1) A fixed nonvarying condition, without motion . (2) Atmospheric noise, as in a receiver.
STATIC ELECTRICITYStationary electricity that is in the form of a charge. The accumulated electric
charge on an object .
STATOR(1) The stationary part of a rotating electrical machine. The stator may be either the field or the
armature, depending on the design of the machine . (2) The stationary member of a synchro that
consists of a cylindrical structure of slotted laminations on which three Y-connected coils are wound
with their axes 120 degrees apart. Depending on the type of synchro, the stator's functions are similar to
the primary or secondary windings of a transformer .
STATUTE MILE5,280 feet .
STEP-BY-STEP COUNTERA counter that provides an output for each cycle of the input in one-step