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TV Antenna's


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

An indoor antenna will work when relatively close to a relatively large city. Rural areas will require an outside antenna. An antenna preamp (low noise high gain amplifier) will improve reception. A preamp can be added to any antenna. Some antennas have built-in preamps.

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 very high gain antenna, to 120° for some indoor antennas. At the beam edge gain is down by - 3 dB, and drops dramatically 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).

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INDOOR ANTENNAs

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

Typical Performance
  • 2 to 4 dBi gain.
  • 20 - 25 miles range.
    Greater range with a preamp.
  • Front & Rear coverage.
    Relatively wide reception area.
  • Mounting / Location:
    Window -- best reception.
    Wall -- good reception.
    Table Top -- good reception.
    Back of TV -- limited reception.
Indoor Antenna Pattern

OUTDOOR ANTENNAs

Most outdoor antennas are directional with best reception in one direction, the main beam. Beamwidth varies from 90° wide for high gain antenna's, to 30° wide for very high gain antenna's.

Some outdoor antenna's have built-in pre-amps, some are detachable. The antenna amplifier gets power (110 Vac house current and/or USB) through the coax cable. The cable between the antenna preamp and the preamp power box cannot have any connections (power splitters, adapters). Also see Amplifiers.

High Gain Antenna
  • 5 to 10 dBi gain.
  • 30 - 50 miles range.
    Greater range with a preamp.
  • Wide beam (up to 90°).
  • Attic or outside mounting.
  • Moderate Size.
Moderate Gain Antenna Pattern


Very High Gain Antenna
  • 11 to 15+ dBi gain
  • 50 - 85+ miles range.
    Greater range with a preamp.
  • Narrow beam (around 30°).
  • Outside mounting.
  • Relatively Large.
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.
    • requires a preamp.
    • well suited for marine or RV use.
  • Rotor Antenna
    • 360° coverage.
    • takes a little 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 2 - 13 54-216 MHz
UHF none none 14 - 69 470-806 MHz
VHF-Hi / UHF 7 - 69 174-216 MHz
470-806 MHz
VHF / UHF 2 - 69 54-216 MHz
470-806 MHz

Also see TV broadcast Frequency.

GAIN (dBi & dBD )

Antenna gain is measured in dBi or dBD. Manufacturer's use a standard dipole antenna (+2.15 dBi) 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.

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+

Range vs Antenna Gain

Also see Antenna Gain Calculator.

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