In radio communication, a radio transmitter antenna radiation contains information on electromagnetic waves, radio receiver arrive at the receiving point of the antenna, it takes a period of a natural path. Radio wave propagation in the natural environment, there are three main paths are commonly used in wireless communication: line-of-sight transmission, and wave propagation, the spread Tianbo. Different wavelengths of radio waves in the spread over three different paths in the dissemination of the law. Short-wave radio waves (2-30Mhz) are different from the spread of the special laws of other bands, only a thorough understanding and application of the laws of their particular can play a short-wave radio communication equipment should be performance, establish a stable and reliable communication links to improve communication quality.

     First, the radio wave propagation path:
     (1) line-of-sight transmission: the spread of means-horizon radio transmission antennas in the antenna and to accept each other "visible" in the mode of transmission distance. Waves in the atmosphere near the ground at low altitude in order to approximate a straight line in the path of transmission, transmission power in certain circumstances, the communication distance to a large extent depends on the two sides to send and receive antenna height, and more for the ultrashort wave communication.
     (2) and wave propagation: ground wave along the surface of the Earth refers to the spread of the wave. When the waves spread along the surface, the sensor surface in the charge, they charge forward with the wave form and current. Due to a certain degree of resistance of the earth, the current consumption of energy to flow out of date, the formation of the absorption wave face. Resistance to the size and frequency of the waves, the higher the frequency, and the greater the absorption. Therefore, wave propagation and suitable for long-wave and medium wave and long-distance radio communication; small short-wave radio in this way only a few kilometers to several tens of kilometers to the close communication. Wave is spread along the surface, essentially free from the impact of climatic conditions, so the signal stability, which is to highlight the advantages of wave propagation.
     (3) the dissemination Tianbo: Tianbo issue refers to the ground by the ionosphere reflects radio waves back to the ground. Short-wave radio station transmitting power can be smaller, do not rely on any ground system Tianbo path alone to establish the use of hundreds of kilometers or even thousands of kilometers of the communications link is different from other means of communication for the outstanding advantages. However, the ionosphere with the day and night, seasonal, annual change, resulting in the spread of the situation in accordance with Tianbo time. Therefore, the dependence of the ionospheric reflection Tianbo established short-wave radio communication is unstable and unreliable (as opposed to other terms of the spread of the path). Long-range short-wave communications equipment operators requirements on short-wave-band radio wave propagation have an in-depth understanding of the law and more practical experience, and relies on communication配合默契parties. Focus on the following wave of short-wave communications and dissemination Tianbo.

     Second, the short-wave and wave propagation:
     The use of ground wave path, a certain distance in the establishment of stable and reliable short-wave communication. Effective distance depends primarily on its short-wave radio transmitter power, antenna set up the way the spread of the path on the impact of the terrain and surface features and the use of the carrier band. In transmission power, antenna set up, the terrain and surface features have been identified, the carrier frequency has become the only communication from the optional factors. In view of the lower frequency radio waves of the earth to absorb the smaller, short-wave radio communications should be chosen to wave the lower short-wave frequency (2 - 6 Mhz). Obviously, the ground wave field strength is inversely proportional to the distance and communication, the farther the distance, the weaker signal strength. As far as a certain distance, the signal / noise ratio will be reduced to no guarantee that the level of reliable communication, leading to disruption of communication. For the purposes of short-wave communications, the noise generated in the atmosphere mainly from the days of electricity and industrial equipment around electrical interference.
     In general, in one case of an elevated antenna, select the appropriate carrier frequency, the use of small short-wave radio wave path can be tens of kilometers away in the establishment of reliable communication.