The Sloper antenna (directional dipole)
Antenna type "sloper" (tilted dipole) is one of the most common. Especially hams often use it in the range of 80 and 40 m, where for carrying out DX relations is very important to have pressed to the ground radiation in the vertical plane.
There are several options of antenna structures "sloper". In Fig. 1 shows "sloper" length 1/2L, Rin = 75 Ohm.
When using a metal mast, the maximum radiation is in the direction of reducing leaf antenna. If the mast is used dialekticheskaya pillar or a tree, the graph will be bidirectional. In Fig. 2 shows "sloper" 1/4L. Rin = 50 Ohms. Metal mast should have a pretty good grounding. since this affects the efficiency of the antenna.
On the basis of such antenna can be made "sloper" on 160. 80 and 40 meters. It works very well on N-H bands, and using the antenna matching device, you can use it on 20. 15, 10 meters.
The antenna shown in Fig. 3. Lengthening coil 160-meter band is performed on the dielectric base, diameter 41 mm, 68 turns (turn to turn), wire PEV-2 in diameter of 1 mm. Its inductance should be about 87,2 µh. As a grounded mast is an integral part of the antenna, a metal guy wire should be broken insulators. Configurable antenna using a SWR meter in the locations shown in Fig. 3.
When using matching device configuration is required, we need only to correctly perform the arm length of the antenna. When using a multi-range version of the shoulder "A" must be calculated on 3500 kHz. But the most effective is "sloper" length 1L (Fig. 4). This antenna requires a large area for its installation, but it's worth it. Rin=75 Ohm. The total length of the antenna curtain is determined by the formula:
If you install a single mast 3-4 such antenna, with an antenna switch, you can choose different directions of radiation. The antenna is not involved in the work should automatically be grounded.
Author: I. Podgorny, UC2AGL; Publication: www.cxem.net