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Log Periodic Antenna for 21, 24, 27, 28 and 30

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ANTENTOP- 02- 2004, # 006

Log Periodic Antenna for 21, 24, 27, 28 and 30



The Log Periodic Antenna works at 21, 24, 27, 28 and 30- MHz. As all antennas of the type, the LPDA is easy tuned and works with a high efficiency. The antenna contains additional directors for 21 and 28- MHz and reflector for 21- MHz.






The 10-element Log- Periodic Antenna (see Figure 1, at page 63) was designed by UA3THQ and modified by me, UW3TU.

S. Ershov, UW3TU,


603000, Nizhniy Novgorod, Box 114






Boom = 7000 mm
G at 28-MHz= 9 dB; F/b=30 dB
G at 24- MHz= 6 dB; F/b=20 dB
G at 2l- MHz =8 dB;

F/b=24 Db

Input resistance at X-X is 200- Ohms


Stuff: Aluminum tubes of 24 mm OD. Vibrators W1 - W7 are isolated from the boom, the gap in all vibrators is 80 mm (see Figure 2). Stub has initial length in 1.5 meters, and made of a copper wire of 1.5- mm diameter


Adjustment of the antenna consists of the selection of a minimum SWR by the length of the stub (see Figure 1) at 21- MHz. After that the SWR should be not more than 1.3:1 at all operated ranges.


Feeding is done by a 50- Ohm coaxial cable through a broadband transformer 1:4.




Radiolubitel # 9, 1992, p. 43


73! DX!




Figure 2




Page 62


62 63



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