Experimental study of a turnstile aperiodic HF-band antenna with a terminal load in the form of a near ground four-arm spiral antenna

It is known that the energy characteristics of four-arm spiral near ground antennas with internal power supply (at the geometric center) vary significantly depending on the order of excitation of their inputs. When excitation of the arms of such antennas in the cross-polarization mode, their efficiency of radiating electromagnetic waves decreases by an order of magnitude or more; the article proposes an excitation method that is free of this drawback. The aim of the article is an experimental study of the comparative effectiveness of a near ground four-arm spiral antenna of the HF-band and the antenna system it is part of, when changing its excitation type (from internal to external) and mode (main and cross-polarization). A detailed description of the design of the antenna system and the method of implementing the excitation of its emitters are proposed. The proposed design of a phase-shifting device based on a Butler matrix can be used for effective electromagnetic waves radiation or reception by an antenna system of both right and left circular polarization. The results of the analysis of methods for excitation of a near ground four-arm spiral antenna presented in the article can be used in the design or modernization of antenna systems of ionosondes or radio centers with increasing their efficiency.