Campbell Scientific RF320-Series Ritron VHF/UHF Radios - Manual (Page 33)

Appendix A. Glossary
caused by the interference of incident and reflective waves traversing the
transmission line. Therefore, SWR can be calculated from the forward and
reflected power measurements as follows:
F R
F R
P P
P P
SWR
−
+
=
1
1
Where:
P
R
= Reflected Power
P
F
= Forward Power
Tone Squelch: A receiver function whereby the audio or data output is
inhibited whenever one of a select number of sub-audible tones or digital codes
is not detected in the received signal. The purpose is to provide a means of
discriminating between received signals. (See also CTCSS and DCS.)
Transceiver: A combination radio transmitter and receiver.
Transmission Line: Specialized conductors, typically in the form of a coaxial
cable, for transferring RF signals between a transceiver and an antenna.
Ultra High Frequency (UHF): Ultra high frequency radio waves that are in
the range of 300 to 3,000 MHz.
Very High Frequency (VHF): Very high frequency waves that are in the
range of 30 to 300 MHz.
Voltage Standing Wave Ratio (VSWR): It is common for SWR to be
expressed in terms of voltage and is then referred to as VSWR (pronounced
“viswar”). Both SWR and VSWR are a measure of how efficiently radio-
frequency power is transmitted from a power source, through a transmission
line, into a load. Perfect = 1.0:1, Good < 2.0 :1. (See also SWR.)
Wattmeter: A term commonly used to refer to an instrument that can measure
the amount of power emitted from a radio transmitter. Generally these devices
can also measure the amount of potentially damaging energy reflected by
connectors, cables, and antennas, back into the radio.
Wavelength: The distance that an electromagnetic wave travels in one
complete cycle.
Wideband Channel: That part of the RF spectrum occupied by the radio’s
emissions having a band width of 25 kHz centered about the channel
frequency. (Note: The FCC has prohibited operation in a Wideband Channel
after January 1, 2013.)
Wind Loading: A characteristic of an antenna or other structure that is a
measure of the forces applied to the structure due to wind.
Yagi Antenna: A narrow band directional antenna named for one of its
inventors, which consists of a boom supporting a series of metallic elements or
rods.
A-5