Overview of Delta Antennas. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Television antennas

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Delta type antennas have long been used by radio amateurs. It is convenient to place it in any version and vertically if there is sufficient height and when there is no space on the roof, but it happens that even at an angle of 45 degrees it is not possible to place the antenna. Therefore, different versions of the Delta antenna and its placement and fastening are proposed.

On fig. 1 classic antenna placement with sufficient suspension height.

You cannot position the antenna at an angle to the ground; you can position it horizontally relative to the ground (Fig. 2. To match the input impedance of the antenna and the feeder, a transformer is used, which is made of RK 75 cable with a length of 13,94 m.

If you have enough space to place the Delta at a 45 degree angle and get the maximum gain from this antenna, then Fig. 3 shows the antenna layout with dimensions. Matching the antenna with the RK 75 power cable does not cause much difficulty. Setting up the antenna reduced by setting to the middle frequency of the range by changing the perimeter of the "Delta" frame, and tuning by SWR by changing the angle of inclination with respect to the ground.

In case of insufficient suspension height, a variant is proposed with the location of the Delta antenna in the horizontal and vertical planes in Fig. 4, while the radiation of the antenna will be directed towards the open arms of the antenna.

With a good elevation difference, if you live in a 9 or 12-storey building, there are 4 or 5-storey buildings in the courtyard or nearby, you can make a directional antenna from 2 Delta antennas, its diagram is shown in fig. 5. This antenna has all the properties of a directional antenna and has a gain in the direction of radiation up to 8 dB. The antenna is structurally located on stretch marks broken by insulators. Powered by RK 75 coaxial cable.

If there are adjacent buildings of the same height, you can make an antenna from 3 Delta antennas fig6. The gain of this antenna up to 9,5 dB is also powered without any matching devices, since the input impedance of this antenna is 75 ohms. Perimeter "Delta" - R = 85.8 meters, Z = 83.3 meters, D = 80.8 meters. The distance between R and Z = 25 meters, and between D and Z = 25 meters. Structurally, the antenna is stretched with stretch marks from a kapron cable with a diameter of 8 - 10 mm with lanyards.

The given antenna fig. 7 of a series of compromises: the low antenna height of 11 meters and the desire to use it in a wide frequency band. To match the input impedance of the antenna, an open line with a resistance of 300 ohms is used, so you can only work through such an antenna through a tuner, this will allow you not only to correctly match, but it also becomes possible to use it in a multi-band version.

Setting up all antennas comes down to installing them in the middle of the range or in the area in which you want to work by changing the perimeter of the antenna frame. The minimum SWR by changing the angle of inclination of your antenna does not cause any particular difficulties. The antenna fasteners must be broken with insulators, preferably from radio porcelain, but they can also be made from other material (textolite, fluoroplast), it is important that the mechanical tensile strength of the insulator is sufficient.

Author: A. Manoilenko (UN9LK); Publication: cxem.net

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