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Encyclopedia of radio electronics and electrical engineering / HF antennas
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Max Blumer (WA1MKP) proposed an antenna designed by him that occupies a minimum of space. The antenna is a loop with a perimeter equal to the wavelength.
The figure explains the intention of the antenna designer. As a basis, a regular frame (left sketch) was taken, fed at points x and y. This frame radiates a vertically polarized wave in two directions perpendicular to the plane of the drawing, the maximum field strength is in the plane A-A'. The frame can be turned into a square, then (without significant loss of efficiency) into a rectangle (middle thumbnail). In this case, the polarization of the wave and the directivity of the radiation will be the same as those of the round frame. If this rectangle is bent 90° first along the lines A-A', and then along the lines B-B' and C-C', the flat loop will turn into a three-dimensional cube (right sketch). The perimeter of the antenna, of course, will be equal to the wavelength (L), and each side of the cube will be only 1/10L.
In this case, the vertical polarization of the emitted wave will be preserved, and instead of a bidirectional radiation pattern, an almost omnidirectional pattern will be obtained.
The stated principle was first implemented in the form of a 144 MHz band antenna. A 50-ohm coaxial cable with a matching device was used for power supply (SWR varied from 1,2 to 1,4 over the range). A study of the radiation pattern using a field strength meter showed that there is a slight difference in the radiation forward-backward (1,8 dB) and forward-sideways (3 dB), the latter was apparently due to the shielding effect of the supply cable and structural elements.
Then WA1MKP made a similar antenna for the 21 MHz band. It had the same characteristics (however, the SWR turned out to be slightly higher). In addition to QSOs with other US states, contacts were made with South America and Europe.
Literature
- "QST" (USA), 1973 No. 2
Publication: cxem.net
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