Simple tri-band antenna
Over a year on my radio station of the second category is operated by a simple antenna (see Fig. 1) which is a modification of the antenna DL1BU. She works in the ranges of 40, 20 and 10 m, does not require the use of a symmetric feeder, agrees well, is easy to manufacture.
As a matching balun element applied on transformer a ferrite ring brand RF section 50 of 2.0 cm2. The number of turns of CSOs primary winding 15 and a secondary - 30, wire - sew-2 with a diameter of 1 mm.
When applying the ring of the other sections need to re-choose the number of turns using the scheme shown PA Fig. 2. As a result of selection it is necessary to obtain the minimum SWR in the range of 10 m.
Made by the author of the antenna has a VSWR of 1.1 to 40 m, 1.3 to 20 m and 1.8 - 10 M.
Author: V. Kononov (UY5VI) Donetsk; Publication: N. Bolshakov, rf.atnn.ru