Television
Antennas

INTRODUCTION
An indoor antenna can work when broadcast towers are within about 20 - 30 miles. In a cluttered environment an outside antenna may be required. An outside antenna can get signals up to 45 - 60 miles or more. An antenna preamp will improve a weak signal and generally reception range. A preamp can be added to any antenna. Some antennas come with a built-in or detachable preamp. Additionally, in many cases a UHF antenna will receive a VHF signal at reduced power, but still strong enough for reception.

Antenna Gain
Antenna gain measures the signal power an antenna captures. Gain is measured in dBi - decibels (dB's) with respect to a lossless Isotropic radiator. Many published antenna gains are in "dB", they really mean dBi. See below.

Digital vs Analog Antennas
There is no difference between a digital antenna and an analog antenna, except the name. Digital and analog TV signals both use the same carrier frequencies. Carrier modulation (digital or analog) does not effect antenna reception.

Flat thin indoor antennas can be window or wall mounted, or table top. Antennas that are only table top come in a variety of configurations, and are generally better for VHF signals. Symmetrical antennas (looks the same from the front and back) have identical reception areas in the front and back. Many indoor antennas come with a built-in or detachable preamp.

Antennas Direct
Indoor Antenna's

ClearStream Eclipse Sure Grip Indoor HDTV Antenna Beam: GAIN: UHF 70° 4.35 dBi

ClearStream Eclipse Amplified Sure Grip Indoor HDTV Antenna Amplifier: Beam: GAIN: UHF 18 dB 70° 4.35 dBi

ClearStream VIEW Wall Frame Amplified Indoor HDTV Antenna Amplifier: Beam: GAIN: UHF VHF-Hi 20 dB 70° 2.4 dBi 1.3 dBi

ClearStream FLEX Ultra-Thin Amplified Indoor HDTV Antenna Amplifier: Beam: GAIN: UHF VHF-Hi 18 dB 70° 3.9 dBi 2.0 dBi

ClearStream Horizon Amplified Indoor HDTV Antenna with Coaxial Cable Amplifier: Beam: GAIN: UHF VHF-Hi 18 dB 60° 3.9 dBi 2.0 dBi

Most antennas are directional and come in 2 basic styles, vertical profile and horizontal profile. Vertical profile antennas are more efficient. Horizontal profile antennas are a little more wind resistant.

Antenna	High Gain	Very High Gain
Gain	5 to 10 dBi	11 to 20 dBi
Beam	60° to 70°	15° to 35°
Range	45+ Miles	60+ Miles
Size	Moderate	Large

Antennas Direct
High Gain Antenna's

ClearStream 1MAX Indoor / Outdoor TV Antenna Beam: GAIN: UHF VHF-Hi 60° 6.8 dBi 2.1 dBi

ClearStream 5 UHF VHF Ultra Long Range Outdoor DTV Antenna Beam: GAIN: UHF VHF-Hi 70° 7.6 dBi 2.6 dBi

ClearStream MAX-V Long Range Indoor / Outdoor TV Antenna Beam: GAIN: UHF VHF-Hi 65° 8.42 dBi 2.8 dBi

Antennas Direct Element Unidirectional UHF VHF Attic Outdoor HDTV Antenna Beam: GAIN: UHF VHF-Hi 60° 9.2 dBi 6.7 dBi

Antennas Direct
Very High Gain Antenna's

ClearStream 2 RV TV Antenna Preamp: Noise Figure: Beam: GAIN: UHF VHF-Hi 18.6 dB 1.6 dB 70° 10.4 dBi 3.1 dBi

ClearStream MAX-V PRO UHF/VHF Indoor/Outdoor HDTV Antenna Beam: GAIN: UHF VHF-Hi 33° 11 dBi 2.5 dBi

Antennas Direct SR15 Unidirectional UHF Attic Outdoor HDTV Antenna Beam: GAIN: UHF 35° 11 dBi

91XG Uni-Directional Ultra Long Range DTV Antenna Beam: GAIN: UHF 24° 17 dBi

DB8e Extreme Long Range Bowtie HDTV Antenna Beam: GAIN: UHF 16.3° 17.4 dBi

Rotor Antennas
These antennas can receive signals from all directions. The rotor requires a power / control cable run to the outside rotor motor. The antenna does take a little time to change directions. The rotation is plus or minus 180° (so the coax cable doesn't wrap around the mast). A rotor can be added to any antenna, some antennas come with a rotor.

Omni Directional Antennas
These antennas can receive signals from all directions simultaneously. They are relatively compact and widely used in marine and recreation vehicles, and homes. Most have built-in preamps. Overall performance is modest, a strong to high normal signal is required.

Your home location and antenna are the main factors that determine reception.

Television stations broadcast in either the UHF or VHF Frequency Band. The VHF band is sometimes subdivided into VHF-Lo and VHF-Hi. Most stations are in the UHF band. All home antennas get UHF channels, some also get VHF channels. Some antennas do not get the VHF-Lo band (RF channels 2 - 6). It's not uncommon for a UHF antenna to get VHF signals. The signal strength is reduced, but may be strong enough to receive.

VHF antennas (54-216 MHz) also receive FM radio (88-108 MHz). A strong FM signal can overwhelm and interfere with a TV signal. An FM trap (notch filter) can eliminate the interference, but may reduce RF channel 6 reception.

VHF antennas are larger than UHF antennas because the wavelengths are longer (lower frequencies). A VHF/UHF antenna combines a VHF and UHF antenna into a single configuration. A built-in coupler is used to combine VHF and UHF signals to the antenna output connection.

See Tech section / Frequency Bands.

Antenna gain is expressed on a logarithmic scale with unit dimensions of dBD or dBi. The dBD unit is used by manufacturers to measure gain, the dBi unit is used for calculations and publications. Antenna gain expressed in dB usually means dBi.

Also see Tech section / The Decibels (dB) Scale

ESTIMATE UHF ANTENNA GAIN FROM SIZE
UHF Antenna gain can be estimated from antenna dimensions and antenna efficiency. Efficiency can be estimated from antenna type. Gain also depends on frequency, higher frequencies have higher gains.

Most antennas are directional and have a specific reception area (main beam). The beams are relatively wide, some wider than others.

RECEPTION PATTERN

RECEPTION AREA

BEAM SPREAD (d)

Beam Spread Calculator
Beamwidth:		° (Degrees)
Range:		Miles kilometers
Beamwidth Range Beam Spread Calculate / Re-calculate

Antenna Polar Plots

Antenna Gain Varies
Antenna gain varies with frequency. The higher the frequency (higher RF channel) the greater the gain. Advertised gains are usually for the highest frequency, and the highest gain. The gain maximum to minimum difference can be 2 dB or less for a low gain antenna, around 4 dB for a high gain antenna, and up to 6 dB or more for a very high gain antenna.

Beam Loss
An antenna has maximum gain when the main beam is directly aligned (0°) to the signal direction. Gain decreases slightly from the beam center (0°) to the beam edge. At the beam edge the antenna gain is down by -3 dB. Past the beam edge (the -3 dB point) gain drops dramatically. Side and back lobes have a negative gain, from -10 dBi to -30 dBi or more.

Polarization Loss
Polarization is the broadcast antenna signal electric field orientation. Polarization loss occurs when the transmit antenna does not match the receive antenna polarization. Virtually all home antennas and many broadcast antennas are horizontally polarized. Some broadcast use circular polarization for better signal propagation in a cluttered and/or bad weather environment. When a mismatch occurs, the receive antenna loss is -3 dB.

Broadcast Pattern Loss
Broadcast antenna patterns can be omni directional (broadcast equally in all directions - 360°), or directional. A home antenna that is outside a directional broadcast main beam will receive less power. The loss can be a few dB to 10's of dB's.

Summary

OTA DTv TV Antennas