TV AntennaTech
Tips
From Winegard
VHF/UHF/FM TV Tech Tips
Don’t use an outdoor TV antenna with bent elements or other
structural damage.
“Fringe Area” is the edges of the TV transmitter signal area where
the signal is weak. The weakest signal area is “Deep Fringe”
usually about 50 miles from the transmitter. If you are receiving
several channels with transmitters in different locations, you
might be in the fringe area of some but not others. To find out if
you are in the fringe area, call the station and ask for
transmitter locations. In fringe areas, you need a large, high gain
antenna and coax with the least loss.
Snow on the screen
If the TV picture looks like it was set in a snowstorm,
you have interference called “snow,” a lack of signal.
Check connections from your set to the wall and coax connection
to the TV antenna — they should be securely connected. A
directional, high-gain antenna or preamp will pull in a stronger
signal.
Ghosting problems
If pictures on your screen have shadows behind them, you have a
ghost problem — your TV set is receiving a second, weaker reflected
signal a split second after the original signal. The other signal
may be bouncing off a tall building or mountain and picked up by
your TV antenna. If you have a left side ghost, probably the
signal is picked up on the downlead; a right side ghost is probably
a reflected signal. An antenna with very sharp directivity is a
solution to ghosting.
A temporary ghosting problem can be caused by a weather
inversion. TV signals that normally go out into space are bounced
back to earth by layers of trapped air; the effect is the same as
signals bounced off a tall object and clears up with weather
changes.
Other reception problems include dark wavy lines on your
picture. This is co-channel interference — for example, if you are
watching channel 12, you are also getting signal from another
channel 12.
Changing the direction of your TV antenna and pointing it more
directly at the channel you want to receive, or installing an
antenna with a higher front to back ratio will probably solve this
problem.
FM signal problems result when the TV antenna receives too much
FM signal causing a herring bone pattern. Most problems occur on
VHF channels. FM traps are available to help alleviate this
problem.
Installing your TV antenna in an attic? Do you
have metal or aluminum backed insulation in the walls or under the
roof? If this insulation is between your antenna and the TV signal,
the signal will be blocked. You’ll have to remove the insulation or
install the TV antenna in a different place.
Although the TV antenna is inside, the narrow end must point
toward the transmitter of the TV station.
What are preamplifiers and how do they work?
Preamplifiers amplify, or strengthen, the signal received
by your TV antenna, but will not increase the range. You can use a
preamp to overcome downlead and splitter loss between the antenna
and the television set. But preamplifiers also amplify interference
and FM signals. Distribution amplifiers are another option for
multiple TV outlets/sets, also amplifying signals. And splitters
are designed to couple or divide signals, but do not amplify the
signal. Winegard has a full line of preamplifiers, amplifiers,
splitters, and other television reception accessories.
Do all TV antennas pick up all the TV stations?
Different types of antenna designs are available. Select
one to receive signals in your area that you want to receive.
82 channel (also called all-channel) picks up VHF channels 2-13,
UHF channels 14-69 and FM radio 88 - 108 MHz.
VHF TV antennas pick up channels 2 - 13 and usually FM band.
UHF TV antennas pick up high frequency channels 14-69.
HDTV TV antennas should pick up both VHF and UHF frequencies.
TV Reception Basics
Local area television
Picture quality
Costs
TV Antenna Components
Boom
Phasing Lines
TV Antenna Downlead
Signal Strength
Local area television
Local area television stations broadcast their signal “over the
air” to conventional TV antennas. Major networks (ABC, CBS, NBC,
FOX, PBS) and local programming (sports, weather, news and local
interest programs) are broadcast to transmitters, which then send
signal to surrounding areas.
Picture quality depends on the television set, type of TV
antenna and distance from station transmitter.
Costs include TV antenna purchase and any accessories needed —
preamplifiers, distribution amplifiers, or splitters for more than
one television set — plus a professional installation fee if
necessary.
A conventional outdoor TV antenna is the most economical choice
for local area broadcasting and local network programming. There is
a onetime investment for the TV antenna, accessories and
installation (if necessary). You pay no monthly subscription cost.
TV Antenna Components
Main components of an outdoor antenna: Elements, Boom and Phasing
Lines.
There are three types of elements:
Director elements: At the front of the TV antenna; smaller
elements which initially pick up the signal.
Driven element: The element where the coax is connected; “Drives”
the signal down the coax to the TV.
Reflector element: Longest element; always located at the back of
the antenna; reflects unwanted signals away and reflects desired
signal from the front of the TV antenna back to the driven
elements.
The Boom is the center section the elements are fastened to. The
Phasing Lines may be small aluminum wires or rugged aluminum braces
— whatever form they are, these phasing lines pass the signal from
the driven elements to the coax downlead. Sometimes the boom will
act as phasing lines, and is called a “hot boom.”
TV Antenna Downlead
Coax cable is used for downlead on outdoor antennas. It can be run
through pipes, stapled to walls, taped to the mast — making it easy
to install. Coax is 95% shielded, excellent noise rejection,
durability and is not affected by weather. RG-6 is the preferred
coax because it has less loss than RG-59 coax.
Television broadcasting stations operate on three bands and
frequencies — VHF (very high frequency) low band, channels 2-6 plus
FM; VHF high band, channels 7-13; UHF (ultrahigh frequency),
channels 14-69.
The FM band is located between channels 6 and 7 on VHF, and is
closest to channel 6. A strong FM station might cause interference
on channel 6 because of its close proximity.
Signal Strength
The broadcast signal strength at your location depends on four
variables:
Distance from transmitter. The farther away you are, the weaker
the signal, resulting in reduced picture and sound quality. UHF
signals are harder to receive than VHF.
With TV signals, there are two carriers in transmission — video
and audio. The video (picture) will dissipate faster than audio, so
sometimes you receive sound but no picture.
The terrain between your location and the transmitter. Unlike AM
signals, which follow the curvature of the earth, TV and FM signals
travel in a tangent to the earth. Other obstructions (high
buildings, hills, etc.) can also interfere with broadcast signals.
Interference caused by buildings, water towers etc. often causes
“ghosting” problems (ghosting is multiple images on your screen) —
the signal from the transmitter is reflected by obstacles; the
signal reflected arrives at your TV set a split second later than
the main signal from the transmitter and causes multiple imaging. A
directional antenna with good side and rear rejection can eliminate
or greatly reduce ghosting. Some ghosting cannot be solved without
moving to another location.
Type and size of TV antenna. The size of your TV antenna is
determined by the distance from the transmitter — TV antenna size,
including length and number of elements, increases as distance
between location and transmitter increases. In extreme fringe
areas, stacking TV antennas (using multiple antennas on the same
mast) is suggested.
Basic types of antennas:
Broadband: Picks up all available channels — VHF broadband
(2-13), VHF/ UHF broadband (2-69), UHF broadband (14-69)
Amount of signal loss in your system. In every system, there is
some amount of loss from antenna to TV set or FM receiver.
Cable Loss: There is some loss for every foot of
cable used, depending on the size of the cable (Bigger cable =
smaller loss); the length (longer length = bigger loss); signal
frequency (more loss on channel 69 than channel 2).
Splitter Loss: Occurs every time the signal coming from the TV
antenna is split. To operate two TV sets, the two-way splitter used
reduces signal 30%; four TV sets, the four-way splitter reduces the
signal 60%.
Feed-thru Loss and Isolation Loss: Usually occur in large MATV
systems (motels, apartment buildings). In 98% of home systems,
these losses will not occur.
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