Since the direction of current of opposite ends of the frame are in antiphase, spurious emissions up is significantly reduced. The radiation pattern in the vertical plane shown in Fig.2, and in the horizontal plane - has pronounced highs and it can be considered circular.
Bandwidth of the antenna is about 100 kHz level VSWR=2. The input resistance is 160 Ohms at the height of the suspension 30 meters (typical 9 storeys) and decreases with decreasing height. Estimates for other suspension height at the resonant frequency of 1.85 MHz are given in table. 1.
Table 1
Height, m
Perimeter, m
BX.resistance, Ohm
20
322,06
75
30
320,88
160
40
321,43
230
50
323,56
280
At the height of the suspension from 20 m to 50 m maximum radiation angle to the horizon in the radiation pattern varies slightly from 48 to 40 degrees, respectively. The antenna was simulated and tested in the range of 2 m and confirmed the design characteristics.
Author: nick Fedoseev, UT2UZ, Kyiv; Publication: N. Bolshakov, rf.atnn.ru