vhf calling distance
Very High Frequency (VHF) refers to the band of radio waves with frequencies ranging from 30 MHz to 300 MHz. It is commonly used for short-range communication in civil aviation and maritime contexts. The communication distance of VHF is influenced by a variety of factors, such as transmission power, antenna height, terrain, and atmospheric conditions. Below is an introduction to the factors affecting VHF communication distance and methods for calculating it.
Transmission Power:
Transmission power refers to the energy of electromagnetic waves output by a radio transmitter. The greater the transmission power, the stronger the electromagnetic wave and the farther the propagation distance. Generally, VHF transmission power ranges from 2W to 50W.
Antenna Height:
Antenna height is the height of the radio antenna above the ground. The higher the antenna, the longer the propagation path of the electromagnetic wave, and the less affected it is by reflection and absorption from the ground, resulting in a longer communication distance. Typically, VHF antenna heights range from 3m to 30m.
Atmospheric Conditions:
Atmospheric conditions include meteorological factors such as temperature, humidity, air pressure, wind speed, cloud cover, and precipitation that are encountered during the propagation of radio waves. These conditions can cause refraction, scattering, and attenuation of electromagnetic waves, leading to variations in signal strength and fluctuations in communication distance.
Calculation Methods for VHF Communication Distance:
There are several methods to calculate VHF communication distance, one of which is a relatively simple approach based on the line-of-sight formula. However, this is only an approximate estimation. The actual communication distance also needs to take into account other influencing factors, such as transmission power, terrain, and atmospheric conditions.
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