Antenna Sloper (Inclined dipole). Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / VHF antennas
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Antenna type "sloper" (inclined dipole) - one of the most common. Especially often, radio amateurs use it in the 80 and 40 m bands, where it is very important to have radiation pressed to the ground in a vertical plane for DX communications.
There are several design options for the "sloper" antenna. On fig. 1 shows a "sloper" 1/2L long, Rin = 75 ohms.
Fig. 1
When using a metal mast, the maximum radiation will be in the direction of decreasing the antenna web. If a dielectric pole or a tree is used as a mast, the diagram will be bidirectional. On fig. 2 shows a "sloper" 1/4L. Rin = 50 Ohm. The metal mast must have a reasonably good earth connection. since the efficiency of the antenna depends on it.
Fig. 2
On the basis of such an antenna, you can make a "sloper" at 160. 80, 40 meters. It works very well on the low bands, and when using an antenna matching device, it can also be used on 20, 15, 10 meters.
The antenna is shown in fig. 3. The extension coil of the 160-meter range is made on a dielectric frame with a diameter of 41 mm, 68 turns (turn to turn), PEV-2 wire with a diameter of 1 mm. Its inductance should be about 87,2 uH. Since the grounded mast is an integral part of the antenna here, the metal guys must be "broken" by insulators. The antenna is tuned using an SWR meter in the places shown in fig. 3.
Fig. 3
When using a matching device, no adjustment is required, it is enough to correctly perform the lengths of the antenna arms. When used with the multi-band option, arm "A" must be sized for 3500 kHz. But the most effective is the "sloper" 1L long (Fig. 4). Such an antenna requires a slightly larger area for its installation, but this is justified by its work. Rin=75 Ohm. The total length of the antenna web is determined by the formula:
Fig. 4
Lm=(936*0,305)/fMHz
Side Am=(702*0,305)/fMHz
Side Bm=(234*0,305)/fMHz
If you install 3-4 such antennas on one mast, then using the antenna switch you can choose different directions of radiation. Antennas not involved in the work must be automatically grounded.
Author: I. Podgorny, UC2AGL; Publication: cxem.net
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