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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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