Given the same sized reflector, which signals, high-frequency, or low-frequency, can be more efficiently focused by a common dish antenna (i.e., result in a higher antenna gain)?

Answer 1

In general, low-frequency signals can be more efficiently focused by a common dish antenna compared to high-frequency signals when using the same sized reflector. This is due to the relationship between the wavelength of the signal and the physical dimensions of the antenna.

1. Wavelength Considerations: The wavelength of a radio signal is inversely proportional to its frequency. Lower frequency signals have longer wavelengths, while higher frequency signals have shorter wavelengths. A common dish antenna is designed to reflect signals effectively when the dimensions of the reflector (such as diameter) are comparable to or larger than the wavelength of the signal.

2. Antenna Gain: Antenna gain is a measure of how well an antenna can focus energy in a particular direction compared to a reference antenna. For effective focusing, particularly with parabolic dish antennas, the ratio of the dish's diameter to the wavelength should generally be significant. If the wavelength is much smaller than the dish size, the antenna can focus that frequency effectively, resulting in higher gain.

3. Efficiency of Focusing: Since low frequencies correspond to longer wavelengths, they fit more comfortably within the dimensions of a given dish antenna. High-frequency signals, on the other hand, have shorter wavelengths, and as a result, they require more precise construction and alignment of the dish to effectively focus the signal. This can lead to lower efficiency and gain when using a common dish of fixed size for high-frequency signals.

Therefore, given a fixed reflector size, low-frequency signals can achieve higher antenna gains by being more effectively focused than high-frequency signals.