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Lug, Terminal–See Terminal Lug.
Mast, Antenna (TV)–A vertical section (or sections)
of tubular steel or aluminum on which the antenna
is mounted. Most sections typically are available in
5 and 10 ft. lengths.
Matching Impedance–See Impedance.
Matching Transformer (TV)–See Balun.
Microvolt (uV)–One millionth of a volt, or 0.000001
volt. The strength of the signals in a TV antenna
system is expressed as so many microvolts (uV).
Generally, to produce an acceptable TV picture, the
strength of the TV signals at the input terminals of a
TV set must be at least 1000 microvolts (uV).
Mismatch, Impedance–See Impedance.
Multiple Array–Two or more antennas mounted on
the same mast with outputs coupled together.
Multiple arrays are used to increase gain (signal
strength) and directivity.
Noise Figure–Generally, a numerical rating that
indicates how much electromagnetic "noise" there
will be at the output of a circuit or system compared
to the noise at the input. If the strength of the noise
is too near that of the picture-producing signal, noise-
produced specks, called "snow," will be produced on
the TV screen. The lower the noise figure of a circuit,
system, or component, the lower the output noise
level will be compared to the output signal level and
in turn, the lower the probability of snow on the
screen of the TV set.
Ohm–The unit of measure of resistance and
impedance. (see Impedance).
Omni-directional (Antenna)–An antenna capable of
intercepting signals from all compass directions
equally well. Such an antenna is nondirectional.
Orangeburg–A type of black pipe that is made of
asphalt-like material and is used for gas vents and
sewers in homes and commercial buildings.
Orient (an antenna)–To aim the antenna in a specific
direction, usually toward the transmitting tower(s) of
the TV stations.
Overloading of Preamp–See Input Capability,
Preamp.
Overloading of Receiver–See Receiver Overload
(TV).
Passive Device–Any signal-handling device (in an
antenna installation) that is not electrically powered
and therefore, does not increase the strength of the
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LOSSARY
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signal. Couplers and splitters are examples of
passive devices.
Picture Carrier (TV)–The part of a TV signal that
contains the video (picture) information. (The audio
(sound) is contained in the sound carrier.)
Pitch Pad–A small piece of neoprene or other
"rubbery" material that is placed under the legs of a
tripod roof mount to cushion the mount and seal
around the anchor bolts that secure the legs to
the roof.
Plaster Strap–A non-metallic strap that is used to
secure wall connectors for 300 ohm twinlead. (Metal
straps cannot be used with twinlead because they
affect its signal-handling characteristics.)
Plumb Bob–A metal weight (usually cone-shaped),
that is attached to a length of cord or string and hung
free from a height to determine whether the line
between two points or the position of a vertical
structure is truly vertical.
Polar Plot–A flat graph that provides a bird's-eye
view of antenna performance characteristics such as
directivity and beamwidth.
Preamp, TV (Preamplifier)–A small amplifying
device that is mounted on the mast or antenna boom
as close to the antenna output terminals as possible,
so that the strength of a very weak signal is increased
(amplified) before it enters the transmission line.
Without this preamplification, the strength of the
already weak signal (1000 uV or less) would be
further reduced as it passes through the transmis-
sion line producing "snow" on the TV screen.
Rafter–One of the parallel beams that form the slope
of a roof.
Rear Rejection–The ability of an antenna to reject
(not receive) signals that approach it from the back.
Receiver Overload (TV)–A condition in which
excessively strong signals cause the picture on the
TV receiver to lose synchronization (vertical and
horizontal roll) or disappear completely. Older model
receivers are more likely to overload than are newer
ones. Frequently, this condition can be eliminated
by readjusting the receiver's automatic gain
control (AGC).
Rotor Alignment Bearing–See Alignment Bearing,
Rotor.
Sensitivity, Antenna–General classifications of
relative antenna gain that indicate approximately
how far from the station transmitter tower(s) an
antenna designed to be used. Examples of these
classifications are suburban, fringe, and deep fringe.
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