Multi-range dual-element DELTA LOOP. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Multi-range dual-element DELTA LOOP. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / HF antennas

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The proposed design of the "DELTA LOOP" is simple. It takes a little material to make it. It has a small windage. The antenna can be mounted in parts at the working height. The advantages include its multi-range (you can use any combination of ranges from 7 to 28 MHz). Moreover, it is possible to place frames for each range at an optimal distance from each other - 0,2 lambda.

The design of the antenna is shown schematically in the figure. To simplify it, the frames of the lowest frequency range are shown on it. Frames for other ranges are located inside. Both elements - the active element and the reflector - have the same dimensions. To adjust the reflector to resonance, extension cables are used. All dimensions of the antenna required for its repetition are given in the table.

Table 1
Range, MHz Frame side, cm Train length, cm Distance between frames, cm Frame height, cm Strut length E from mast, cm
7 1450 100 869 1240 844
10 1011 70 607 864 589
14 724 60 434 619 422
18 564 50 338 482 329
21 483 45 289 412 282
24 410 40 246 350 239
28 359 40 215 308 210

The antenna is assembled in the following sequence

First, on the traverse B, you need to fix (through insulators) frames to the lowest frequency range, and also place insulators for active elements and reflectors on the remaining planned ranges and thread nylon cords into them. On the mast (reducer) A, a rack B with a traverse C and a cross D is installed. If necessary, stretch marks D are tied to the rack B, the ends of which hang freely.

On spacers E in pre-marked places, the corners of the frames of the remaining ranges are fixed alternately through insulators. At the ends of the struts E, stretch marks Zh with a "floating" insulator and I are tied. The length of the stretch marks Zh should be greater than the distance between the frames (see table) of the lowest frequency range. Stretch marks 3 are tied to the ends of the struts E. The struts E themselves are inserted in turn into the crosspiece G and fixed. Cross G in the desired position is fixed with locking screws.

Multi-range dual-element DELTA LOOP

Using extensions 3 and I, they pull the extreme frames and fix the spacers E. The remaining frames are pulled with nylon cords threaded into the insulators of the traverse B. If there are stretch marks D, they are tied to spacers E as far as possible from the mast.

For spacers E, you can use bamboo, wooden slats, duralumin pipes, divided into two or three sections by insulators. Stretch marks Zh and 3 are made of steel, galvanized pieces of wire 50 ... 80 cm long with a diameter of 1,5...2 mm, interconnected by insulators. The latter can be made of fiberglass with a thickness of 4 ... 8 mm. Steel wire with a diameter of at least 2,5 mm is used as guy wires, since they bear the main load in strong winds.

The active vibrator is fed from the corner, with the central core of the 75-ohm coaxial cable connected to the vertical part of the frame, and the screen to the horizontal. This ensures the efficiency of the antenna at a low height of its suspension. The reflector is adjusted at the working height using a simple field strength indicator. In this case, it is necessary to achieve maximum radiation "forward".

In conclusion, it should be noted that the gain of the described antenna is comparable to the gain of the "double square" - 6 ... 8 dB, but its total efficiency is higher. By the way, I mention this in many amateur radio handbooks, for example, in the "ARRL Handbook".

Author: Nikolai Lavreka (UX0FF), Izmail; Publication: N. Bolshakov, rf.atnn.ru

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