18WuD2x

atio detector • reactance 583
diodes is reversed and the junction point of the
load resistors is grounded. In an FM circuit using
a ratio detector, no limiter is required. The ratio of
the direct-current outputs is proportional to the
ratio of the instantaneous signal voltages applied
to the two diodes.
ratio meter An instrument that compares two different
signals (and indirectly their sources) and
delivers a reading of their ratio.
rational number A number that can be expressed
in the form a/b, where a and b are integers and b
is not equal to zero.
rational operation Any of the conventional arithmetic
operations: multiplication, division, addition,
or subtraction.
ratio of geometric progression In a geometric
progression, the ratio of one value to the next.
ratio of similitude The ratio of the lengths of corresponding
sides in similar geometric figures.
rat race See HYBRID RING.
raven red A variety of red oxide of iron, a commercial
red paint used as the magnetic coating of
early recording tapes.
raw ac Unrectified alternating current (ac) or voltage.
raw data Data that has not been processed in any
way.
rawinsonde A RADIOSONDE tracked by a radio direction
finder to determine wind velocity. The
name is an acronym from radar wind radiosonde.
raw tape See BLANK TAPE.
ray 1. A line of radiant energy. Such a line (e.g.,
the path of a single photon of visible light) is
imagined to arise from a point source and have
zero width. 2. A thin beam of radiant energy
(e.g., the beam of electrons in a cathode-ray
tube). 3. A quantity of radiant energy or ionizing
radiation (e.g, gamma ray). 4. One of numerous
lines converging toward, or emanating from, a
specific point. 5. A vector representing the direction
in which an electromagnetic field or acoustic
disturbance travels. 6. Also called half line.
The set of points on a line consisting of a defined
origin and all the points on one side of the origin.
Example: the positive reactance axis in an AR-
GAND DIAGRAM.
Raydist A continuous-wave, medium-frequency
radionavigation system. The position is determined
according to the phase difference between
two signals transmitted from different locations.
Rayleigh-Carson theorem An expression of the
reciprocal relationship between the transmitting
and receiving properties of an antenna. If voltage
E applied to antenna A causes current I to flow at
a given point in antenna B, then the same voltage
(E) applied at that point in antenna B will produce
identical current I (same magnitude and phase)
at the point in antenna A, where voltage E
originally was applied. Also see RECIPROCITY
THEOREM.
Rayleigh distribution A probability-density function,
used to describe the behavior of sky-wave
electromagnetic signals.
Rayleigh’s law The hysteresis loss in a magnetic
material varies in proportion to the cube of the
magnetic induction.
Rb Symbol for RUBIDIUM.
R B Symbol for BASE RESISTANCE. (Also, r B .)
RC 1. Abbreviation of RESISTANCE-CAPACI-
TANCE. 2. Abbreviation of RADIO-CON-
TROLLED. 3. Abbreviation of REMOTE CONTROL.
R c 1. Symbol for COLLECTOR RESISTANCE. (Also,
r C .) 2. Symbol for COLD RESISTANCE.
RCA jack See PHONO JACK.
RCA plug See PHONO PLUG.
RC circuit See RESISTANCE-CAPACITANCE CIR-
CUIT.
RC-coupled amplifier See RESISTANCE-CAPACI-
TANCE-COUPLED AMPLIFIER.
RC coupling See RESISTANCE-CAPACITANCE
COUPLING.
RC filter See RESISTANCE-CAPACITANCE FILTER.
RCL 1. Abbreviation of RECALL. 2. Abbreviation of
RESISTANCE-CAPACITANCE-INDUCTANCE.
RCM Abbreviation of RADAR COUNTERMEA-
SURES. (Also, radCM.)
RC phase shifter See RESISTANCE-CAPACI-
TANCE PHASE SHIFTER.
RC time constant See RESISTANCE-CAPACI-
TANCE TIME CONSTANT.
RCTL Abbreviation of RESISTOR-CAPACITOR-
TRANSISTOR LOGIC.
RC tuning See RESISTANCE-CAPACITANCE TUN-
ING.
RCV Abbreviation for receive. (Also, rcv.)
RCVR Abbreviation for RECEIVER. (Also, rcvr, rx.)
rd Abbreviation for rutherford.
R & D See R AND D.
R D Symbol for DRAIN RESISTANCE.
R d 1. Symbol for DIODE RESISTANCE. (Also, r d .)
2. Symbol for DISTRIBUTED RESISTANCE.
R-DAT Abbreviation of ROTARY DIGITAL AUDIO
TAPE.
R dc Symbol for DC RESISTANCE. (Also, r dc .)
RDF Abbreviation of RADIO DIRECTION FINDER.
Re Symbol for RHENIUM.
R e Symbol for EMITTER RESISTANCE. (Also, r E .)
REA Abbreviation of Rural Electrification Administration.
reachthrough See PUNCHTHROUGH.
reachthrough region See PUNCHTHROUGH RE-
GION.
reachthrough voltage See PUNCHTHROUGH
VOLTAGE.
reactance Symbol, X. Unit, ohm. The opposition
offered to the flow of alternating current by pure
capacitance, pure inductance, or a combination
of the two. Reactance introduces phase shift. Also
see CAPACITIVE REACTANCE and INDUCTIVE
REACTANCE. Compare RESISTANCE.