Campbell Scientific RF320-Series Ritron VHF/UHF Radios - Manual (Page 30)

Appendix A. Glossary
Dipole Antenna: The most common wire antenna. Length is equal to one-half
of the wavelength for the frequency of operation. Fed by coaxial cable.
Dummy Load: A device that serves as a transmitter’s antenna without
radiating radio waves. Generally a resistive device that’s impedance is matched
to the transmitter.
Duty Cycle: A percentage of the time “on” (transmitting) versus the time “off”
(not transmitting).
Effective Isotropic Radiated Power (EIRP): Same as ERP except that
antenna gain is defined as being relative to an isotrope rather than a dipole.
(See ERP.)
Effective Radiated Power (ERP): The product of the transmitter peak
envelope power, expressed in Watts, delivered to the antenna, and the relative
gain of the antenna over that of a half-wave dipole antenna.
EMI/RFI: Electro Magnetic Interference/Radio Frequency Interference. Broad
spectrum noise or interfering signals.
Fade Margin: The amount of reduction or loss in a signal along a signal path,
measured in dB, caused by environmental factors such as terrain, atmospheric
conditions etc., that can be tolerated before it is no longer sufficiently higher
than the receiver sensitivity. (See also Link Budget.)
Federal Communications Commission (FCC): A board of commissioners,
appointed by the President, having the power to regulate wire and radio
telecommunications in the United States.
Frequency: The number of cycles of alternating current in one second,
measured in Hertz (Hz).
Frequency Modulation (FM): An analog modulation technique whereby the
frequency of a carrier is varied to encode information.
Full-Duplex Transmission: A channel that allows transmission in two
directions at the same time.
Gain: The relative increase in power or magnitude of a signal typically
measured in decibels (dB).
Ground: A connection between a device or circuit and the earth or some
device serving as the earth.
Half-Duplex Transmission: A channel that allows transmission in only one
direction at a time, switching back and forth between transmit and receive.
Hertz (Hz): One completed alternating cycle per second. Named after Heinrich
R. Hertz, a German physicist. Used as the international unit of frequency.
Impedance: A measure of the total opposition to current flow in an alternating
current circuit, made up of two components, ohmic resistance and reactance,
and usually represented in complex notation as Z = R + iX, where R is the
ohmic resistance and X is the reactance.
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