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Television Antennas

PAGE CONTENTS-- Bands | Gain | Indoor Antennas | Outdoor Antennas | UHF Antennas | Multi-Directional

VHF/UHF vs UHF antenna INTRODUCTION
Indoor antennas may be sufficient for receiving full power broadcast less than about 20 or 25 miles away, if there is a relatively clear line-of-sight. Attic mounted antennas will have greater range, but there is at least a 3 dB loss compared to outside antennas. Outside antennas work the best, but are more difficult to install and should be properly grounded for best reception and safety (see Installation). A preamp mounted on or close to the antenna will extend range in most cases (see Amplifiers).

The higher the antenna is above ground level, the greater the signal density. The higher the antenna is above ground clutter, the lower the signal loss.

Antenna size is proportional to wavelength. UHF antennas are smaller than VHF antennas because UHF wavelengths are shorter. UHF wavelengths vary from 1 to 2 feet, VHF varies from 5 to 17 feet. A VHF/UHF antenna is actually 2 separate antennas built into one. The smaller UHF elements are built-in or around the larger VHF elements, and the UHF and VHF signals are combined at the antenna output port.


ANTENNA BANDS (VHF / UHF)
Television antennas are designed to receive up to 3 frequency bands; VHF-Lo, VHF-Hi, and UHF. Most stations are in the UHF band, and most areas have at least one VHF station. Antennas on the market are available in 4 common configurations.

Frequency Band
Band RF
Channels
Frequency
VHF-Lo 2 - 6 54 - 88 MHz
VHF-Hi 7 - 13 174 - 216 MHz
UHF 14 - 69 470 - 806 MHz
Market
Antennas
RF
Channels
VHF 2 - 13
VHF / UHF 2 - 69
VHF-Hi / UHF 7 - 69
UHF 14 - 69

VHF and VHF/UHF antennas will also pickup FM radio (just above RF 6), aircraft voice (AM), amateur radio, police, fire, ambulance, business, public services.

Also see TV broadcast Frequency.

ANTENNA GAIN AND BEAM
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
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 coverage

The larger the antenna, the more signal captured, the more narrow the beam, and the higher the gain. Gains vary with antenna and frequency from around 2 to 15 dBi (0 to 13 dBD).

Antenna Gains (dBi)
Indoor Antenna 2 to 4
Moderate Gain 6 to 10
High Gain 11 to 15

Antenna beam width varies from less than 30° for a high gain antenna, to about 90° for a moderate gain antenna. At the beam edge gain is down by - 3 dB, and drops rapidly past the edge. Also see Reception Factors / Beam Loss.


INDOOR ANTENNAS
Indoor antenna gain varies from about 2 to 4 dBi without a preamp. Gain is proportional to physical area (square inches, in2 etc.).

Indoor Antennas (VHF / UHF)
40 in2
70 in2
75 in2
Preamp
135 in2
Preamp
155 in2
Preamp
90 in2, ultra thin

OUTDOOR ANTENNAS
Manufacturer antenna published ranges are based on a Full Power station, 1000 kW for UHF and 185 kW for VHF signals. Antenna gain can roughly be approximated from range.

Range
Miles
Gain
20 3 dBi
30 6 dBi
35 8 dBi
40 9 dBi
45 10 dBi
Range
Miles
Gain
50 11 dBi
60 12 dBi
65 13 dBi
75 14 dBi
85 15 dBi


Outdoor Antennas (VHF / UHF)
30 Miles
45 Miles
60 Miles
UHF 70, VHF 25 Mi
75 Miles
14.1 dBi
Preamp, 70 Miles

Outdoor UHF Antennas
45 Miles
60 Miles
60 Miles
70 Miles
70 Miles
70 Miles
Preamp, 80 Miles

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Distant and spread out broadcast headings may require multiple antennas, an omni directional (360° coverage) antenna, or a rotor antenna. Multiple antenna systems have greater losses (see Installation Section) and limited angle headings. Omni antennas require a preamp to compensate for low gain (wide beam). A rotor system has the advantage of good gain and full 360° coverage, a disadvantage is it takes time changing angles. Most rotor antennas have a built-in amplifier.

Outdoor Multi Directional Antennas
Omni / Preamp
Omni / Preamp
UHF 65, VHF 55 Mi
Rotor
60 Miles
Rotor
Preamp

Rotor Only

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