Rectangular shown at Figure 1 has good parameters and
not so sensitive to height (that is very important for low amateurs
HF-ranges) compare with dipole. Upper horizon wire is broken by
a nut insulator at it’s center. Due to
a small height the antenna is suitable for 80- and 40-meters Band.
However, it should not be any high objects near the antenna (that
do “shadow” to the antenna). Distance between low wire and roof
or ground may be several tens centimeters.
Input impedance of the antenna may depend on installation
conditions. Matching of the antenna with the feeder provides by
choice of a feeding point at low horizon wire. At corner feeding
the antenna has input impedance near 30-40-Ohms. The more far
the feeding point from the corner is- the more input impedance
(up to several thousands Ohms) would be. Feeder is going along
antenna wires then from the middle of a vertical side the feeder
is going aside (to any direction). For good symmetrical it is
desirable to connect the braid of the coaxial with antenna.
Radiation parts at the antenna are the vertical sides.
For increasing of the efficiency of the Rectangular the sides
should be made from aluminum tubes in diameter 10- 20-mm. Horizon
sides of the antenna provide very low radiation (because the currents
distribution at the antenna), so, they could be made from antenna
wire in diameter of 1-2 mm. Figure 2
shows the currents distribution at the Rectangular (made by MMANA).
antenna has gain near 2- 3 dBi, pass-
band (at SWR 1.5:1.0) near 2% from the center frequency.