TV Antenna Terms Glossary - G to P

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Gain

Gain is a measure of how much signal the antenna will collect. The gain varies according to the direction. If the maker specifies a gain for the antenna, it refers to the gain in the antenna’s best direction. A higher best gain always results in a narrower beam. No antenna has the exact same gain for every channel.

Antenna gains are usually specified in dBd or dBi. If the gain is specified as “X dBd”, that means that the antenna is X dB better than a half-wave dipole. “X dBi” means X dB better than an isotropic antenna. A dBi figure is always 2.15 dB higher than a dBd figure. (That is, the gain of a half-wave dipole is 2.15 dBi.)

Manufacturer’s gain specs are notoriously unreliable. Buyers beware!

Gamma match

This is a geometry that allows the driven element to be connected directly to a 75-ohm coaxial cable, no balun needed. Its problem is that it works well for only one channel. Even makers of single channel Yagis tend to avoid this solution since single channel Yagis are often used for viewing other channels that are strong.

Yagi antenna

Ghosts (see Multi-path interference)

Ground plane antennas (see Vertical antennas)

Guy wires

Guy wires are support wires that hold the mast up. They are necessary when the mast is mounted on the ridge of the roof.

Since guy wires are usually steel they can disrupt the antenna, lowering its gain. To avoid this, keep the attachment point at least 1200mm below the VHF antenna boom (600mm for UHF).

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HDTV antennas

There is nothing different about an antenna for DTV or HDTV. Unscrupulous people have used this as a marketing ploy. The honest antenna makers have had to re-label their products to avoid losing sales.

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