The review of Delta antennas
Antenna type Delta long been used radio Amateurs. It's handy to have in any options and vertically in the presence of sufficient height and when there is no space on the roof, but it happens that the angle is not 45 degrees able to place the antenna. Why are different embodiments of the antenna of the Delta and its placement and mount.
In Fig. 1 classic placement of the antenna at a sufficient the height of the suspension.
You can't place the antenna at an angle to the ground can print horizontally relative to the surface of the earth Fig. 2. For matching the input impedance of the antenna and supply of feeder, transformer is used, which made from cable RK-75 length - 13,94 m.
If you have enough space to place A Delta angle of 45 degrees and get the maximum the gain of this antenna at Fig. 3 provides a diagram the placement of the antenna with dimensions. Approval antenna with a feed cable RK-75 not much difficulty causes. Adjusting the antenna is reduced by at medium setting the frequency range by changing the perimeter of the frame "Delta", and setting the SWR by changing the angle of inclination in relation to the earth.
When there is insufficient height suspension offer a variant location of antenna "Delta" in the horizontal and the vertical plane in Fig. 4, wherein the radiation antenna will be directed toward the uncovered shoulders of the antenna.
With good elevation if you live in a 9 or 12 storey house, in the yard or close by there are 4 or 5 total at home, you can make a directional antenna, 2 antennas Delta, its diagram is shown in Fig. 5. This antenna has all the properties of a directional antenna and has the gain in the direction of radiation of up to 8 dB. The antenna is structurally located on the stretch of broken insulators. Powered coaxial cable RK-75.
In the presence of adjacent buildings of the same height it is possible to make the antenna 3 antennas "Delta" is. The gain of this antenna to 9.5 dB is supplied without any matching devices because the input resistance this antenna 75 ohms. The perimeter of the "Delta" - R = 85.8 m, Z = 83.3 m, D = 80.8 meters. The distance between R and Z = 25 meters, and between D and Z = 25 meters. Structurally, the antenna stretched by the stretch of nylon rope diameter 8 - 10 mm with lanyards.
The antenna Fig. 7 of a series of trade-offs: small suspension height of the antenna 11 meters and a desire to use it in a wide band of frequencies. To match the input resistance of antenna used open line impedance of 300 Ohms, so work through this the antenna is possible only through the tuner, this will allow you not only correctly negotiate, but also provides an opportunity use many band version.
Tuning of the antenna is reduced to install them on the middle of the range or on the area in which you want to work by changing the perimeter of the frame antenna. Minimum SWR by changing the angle of your antenna and special difficulties does not cause. Backstay antenna mounts needs to be broken insulators preferably from radioparty, but the fit of another material (PCB, PTFE) it is important that the mechanical strength of the insulator in the gap was sufficient.
Author: A. manoylenko (UN9LK); Publication: www.cxem.net