Method for Calculating the Radius of an Electromagnetic Availability Zone based on a Surface Wave Source with a Given Spectrum Density of an Isotropically Emitted Signal

Thematic justification. When planning HF radio communication using surface waves, it is necessary to determine the signal-to-noise ratio at the inputs of each radio link receiver. Given a sufficiently high ratio, a conclusion can be drawn concerning the effective functionality of the analyzed radio link in a radio communication system. The planning process will be significantly simplified if the radius of the electromagnetic availability zone (REAZ) can be defined for surface waves at each radio station. Thus, the task of developing a methodology for engineering calculation of REAZ is relevant and practically important.

Goal. To develop an estimating technique for engineering calculations of a REAZ based on a surface wave source with a given isotropically emitted signal spectrum density.

Results. A technique for calculation of the radius of the electromagnetic accessibility zone was developed. A general approach for determining the limiting length of radio links of surface waves is proposed, based on the introduced "technical factor of a radio link" concept.

Practical implications. Nomograms for determining the radius of an electromagnetic accessibility zone were constructed. The dependence of the maximum temperature of external noise on frequency in the HF range can be approximated using an analytical expression. The developed frequency dependence of the temperature coefficient of the input of an ShT4N81 antenna is presented in a graphical form. The feasibility of using the proposed technique for solving practical problems is demonstrated on the example of calculating the radius of the electromagnetic accessibility zone of a TTR-2101M radio station for a monopulse direction finder with a ring antenna array consisting of eight elements of the ShT4N81 type.

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