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Element, Antenna–The small, hollow metal rods of
various lengths that are attached (usually perpendic-
ularly) to the main horizontal support member (boom
or crossarm) of the antenna. The element at the rear
of the antenna (called reflector) is usually the longest.
The element that actually feeds the intercepted signal
to the antenna output is called a dipole.
F-Connector–A small, metallic, male-type connecting
device with internal threads that attach to the end of
a coaxial cable to secure and electrically connect the
coax to a female F-fitting. The internal threads of the
male connector screw onto the external threads of
the female connector. Most baluns have a female-type
F-connector on one end for the 75 ohm coax, and
terminal lugs on the other end for 300 ohm twinleads.
Field Strength Meter–An electronic instrument that
measures the strength of a signal and indicates it on a
meter calibrated in microvolts (uV) or decibels (dB).
(See Microvolt/Decibel.)
Filter, High-Pass–See High-Pass Filter.
FM–The term means frequency modulation. In
relation to television and antenna systems, "FM"
refers to the frequency modulated signal (FM radio
stations whose frequencies lie in a band between TV
channels 6 and 7).
Front-to-Back Ratio–A measure of the directivity of an
antenna that is based on the difference between the
strengths of signals received from the antenna front
and those received from the back. The difference
usually is expressed in decibels (dB). For example, a
front-to-back ratio of 40 dB indicates that the output
strength (in uV) of signals received from the antenna
front will be 100 times greater than those received
from the back. Generally, the higher the rating in dB,
the greater the directivity of the antenna.
Gain–An increase in signal strength. The "gain" of an
antenna indicates how much more signal strength it
delivers to the output terminals than would a single-
element antenna (a dipole) under the same reception
conditions. Antenna gain usually is expressed in
decibels (dB). For example, an antenna with 10 dB
gain will deliver 3.2 times more signal strength to the
output terminals than will a single-element antenna.
Ghosts (ghosting)–Faint duplicate images that appear
in a TV picture to either the left or right of the desired
picture image.
Ground Rod–A long metal rod that is driven into the
ground near an antenna installation and to which is
attached the grounding wires from the mast and
antenna discharge unit to discharge static electricity
to ground before it can enter and damage the
TV receiver.
Guy Wire (Guying)–Three or more multi-strand steel
or aluminum wires that are connected between the
guy ring(s) on the antenna mast and widely spaced
eye screws in the house roof, supporting the mast
against the forces of wind and ice.
Guy Ring–A circular metal collar with attachment
holes (eyes), that is slipped on and clamped to an
antenna mast. Guy wires are then attached to the
mast through the holes in the guy ring.
High Band TV–The band of frequencies assigned to
VHF TV channels 7 through 13 by the Federal
Communications Commission (FCC).
High-Pass Filter–A device that is connected to a
transmission line to filter out interfering signals
whose frequencies are below those in the TV band.
High-Pass Filters typically are used to filter out
interference caused by Amateur and Citizens Band
radio transmission.
Impedance–A signal-affecting characteristic that is
present to some degree in all electrical conductors
(wires) and electronic circuits. Impedance is usually
expressed as so many ohms. To prevent an unneces-
sary decrease in the strength of a signal that is being
transferred (coupled) from one type of conductor or
circuit to another, the difference in impedance must
be "matched" by a device that compensates for the
differences in the impedances. A balun is used in
antenna systems to compensate for the differences in
impedance between a 300 ohm antenna and a 75 ohm
coax, and between a 75 ohm coax and the 300 ohm
input circuit of a TV receiver. Impedances that are not
the same, or whose differences have not been
compensated for, are said to be mismatched.
Input Capability, Preamp–The maximum strength
of signal, in microvolts (uV), that an antenna preamp
can accept without "overloading." (Overloading
causes distortion, reduction, or complete elimination
of the signal.)
Insulator, Acrylic–See Acrylic Insulator.
Interaction, Signal–The interfering effect that one
signal has on another when two different signals are
present that same time in a conductor (wire) or
circuit. Signal interaction in the transmission line of a
TV antenna system causes picture problems such
as ghosting, smearing, snow, and various forms of
interference patterns.
Line, Transmission (TV)–See Transmission Line.
Low Band (TV)–The band of frequencies assigned to
VHF TV channels 2 through 6 by the Federal
Communications Commission (FCC).
G
LOSSARY
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