Loop antenna "DELTA LOOP" that is located so that its upper left corner is at the height of a quarter wave above ground, and power is supplied to the gap of the loop in one of the bottom corners, has a great level of radiation is vertically polarized wave at a small, of the order of 25-35° angle relative to the horizon, so you can use it to conduct distant QSOs [1].
This radiator was built by the author, and its optimal size range of 7 MHz is shown in Fig.1.
The input impedance of the antenna measured on 7,02 MHz, 160 Ohm, so for optimal alignment with the transmitter (TX) having an output impedance of 75 Ohms, applied matching device of the two serially connected quarter-wave transformer of the coaxial cables 75 and 50 Ohm (Fig.2). The antenna impedance is transformed first in 35 Ohms, then 70 Ohms. CWS not exceed 1.2. If the antenna is removed from the holding of more than 10...14 meters, to points 1 and 2 (Fig.2) you can connect a coaxial cable with a characteristic impedance of 75 Ohms required length. Is shown in Fig.2 the size of a quarter-wave transformers are valid for cables with polyethylene insulation (VP 0,66).
The test antenna was made with ORP transmitter 8 watts. Telegraph QSO with hams from Australia, New Zealand and the USA have confirmed the effectiveness of the antenna when working on long-distance routes. For more information on adjusting and measuring parameters of antennas can be found in [2].
Literature
1. Z. Bieńkowski, E. Lipinski. Amateur antenna short and ultrashort waves. Moscow 'Radio and communications", 1983, translated from Polish.
2. K. Rothermel. The antennas. Moscow "Energy" 1969, translated from German.
Author: Igor Zakharov, UR5EFX, Dnipropetrovsk; Publication: N. Bolshakov, rf.atnn.ru