In 60-ies of the Amateurs were popular antenna G4ZU, also known under the name "bird cage". Over time, however, due to the relatively small gain values and attitudes radiation "back and forth" forgot about it.

Experimenting with various antennas, UV6AF and UA6APE modified the specified antenna: positioned it horizontally and changed the feed point. It is possible to obtain certain advantages over the original version of the antenna G4ZU, namely: increased the distance between the current loops of the active element and the reflector; parameters and antenna configuration with parameters and settings "double square"; the antenna design has become more flat, which has simplified its rotation; decreased (compared to "double quadcom") the required number of insulating spacers - must be isolated only "boom" (it may be made of metal tubing with dielectric inserts).

Modified birdcage antenna

The disadvantage of the antenna should be considered as the need of the use of high quality insulation material at the points b and C for isolation of the driven element and reflector, since at these points the highs voltage.

Antenna long time was tested by the authors on the 10 - and 20-meter bands. The ratio of the radiation "back and forth" was more than 30 dB, and the gain was about 7...8 dB. Unfortunately, the authors did not measure the input impedance of the antenna.

Literature

  • Radio No. 11 of 1982
  • Publication: www.cxem.net

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