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TV Antenna Options


Contents -- Indoor Antenna's | Outdoor Antenna's | Multi-Directional | Bands | Reception Area | Gain

As a general rule, the larger the antenna:

Some antenna's have a built-in preamp (low noise high gain amplifier). A preamp can extend range in most circumstances. The amplifier gets power through the coax cable.

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Indoor Antenna Pattern
INDOOR ANTENNAs

Most indoor antennas get best reception directly in front or back of the antenna.

Gain varies from about 2 to 4 dBi without a preamp (passive antenna). Indoor antenna's are usually limited to 20 or so miles range depending on conditions (terrain, obstructions, elevations, etc.).

Many indoor antenna's have a built-in or a detachable preamp. The preamp's are powered by 110 Vac (house current) and/or a USB connection.

Some indoor antenna's mount directly to the TV connector (loop or stick antenna's), and are mostly out of sight. These antenna's work well for strong signals. Table top antenna's are easy to place and angle, and have good performance for moderate sigals. Thin flat antenna's are relatively easy to mount, and have the best performance.


OUTDOOR ANTENNAs

Most outdoor antennas are directional with best reception coverage in one direction between 30° and 60° wide (beamwidth).

An Outdoor High Gain antenna is usually required for tower distances greater than 25 or 30 miles. Most high gain antennas are sized to fit in most attics. A Very High Gain antenna is usually required for ranges greater than 50 or 60 miles, and are too large for most attics.

Some outdoor antenna's have built-in pre-amps that extend range in most circumstances. These antenna's require a power source, and use the coax cable to supply the amp with power. Also see Amplifiers.

High Gain Antenna
  • can mount outside.
  • sized to fit in most attics.
  • good coverage.
  • 5 to 10 dBi.
  • 30 to 50 miles
Moderate Gain Antenna Pattern


Very High Gain Antenna
  • mount outside.
  • too large for most attics.
  • less coverage.
  • 11 to 15+ dBi
  • 50 - 85+ miles
High Gain Antenna Pattern



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MULTI-DIRECTIONAL ANTENNAs

A multi directional antenna system is required for distant and spread out broadcast headings. Most of these systems require 110 Vac power (house current) to run a preamp and/or rotor. A rotor system has the advantage of good gain and full 360° coverage. A high gain antenna with a built-in preamp mounted on a rotor has the highest performance.

  • multiple antennas
  • omni directional (360°) antenna
    • relatively small.
    • require a preamp.
    • well suited for marine or RV use.
  • rotor antenna
    • 360° coverage
    • takes time to change angles.
    • Highest performance.

FREQUENCY BANDS ( VHF / UHF )

Television antennas are designed to receive up to 3 frequency bands; VHF-Lo, VHF-Hi, and UHF. Most TV stations are in the UHF band, and most areas have at least one VHF station. Television antenna's are available in 4 common configurations.

Antenna RF Channels Frequency
VHF RF 2 - 13 54-216 MHz
UHF none none RF 14 - 69 470-806 MHz
VHF-Hi / UHF RF 7 - 69 174-216 MHz
470-806 MHz
VHF / UHF RF 2 - 69 54-216 MHz
470-806 MHz

Also see TV broadcast Frequency.


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RECEPTION AREA

Most antenna's are directional and must be pointed in the broadcast tower direction for best reception. Antenna's can pickup signals from all directions, but signals not in the main beam are greatly reduced.

RECEPTION PATTERN
Antenna 3D Plot
RECEPTION AREA
antenna coverage

Antenna beam width varies from less than 30° for a high gain antenna, to 120° for some indoor antenna. At the beam edge gain is down by - 3 dB, and drops rapidly past the edge. Also see Reception Factors / Beam Loss.

Omni directional antenna's receive signals equally from all directions, but require a built-in preamp (and power source).

GAIN (dBi & dBD )

Antenna gain is measured in dBi or dBD. Manufacturer's use a standard dipole antenna to measure gain in dBD. The dBi unit is used for calculations. Be suspicious of antenna gain expressed in "dB", this can mean anything.

dBi = dBD + 2.15
dBD = dBi - 2.15

Convert to dBi or dBD

dBi - decibels (dB's) compared to a lossless isotropic radiator.
dBD - dB's compared to a standard half wave dipole antenna with a gain of +2.15 dBi.

Antenna range can roughly be approximated from gain.

Range vs Antenna Gain
Gain +dBi Miles
Low / Moderate 2 to 4 20 to 30
High Gain 5 to 10 30 to 50
Very High Gain 11 to 15 50 to 85+

Also see Antenna Gain Calculator.

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