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.
Log- Periodic Antenna (see Figure
1, at page 63) was designed by UA3THQ and modified
by me, UW3TU.
603000, Nizhniy Novgorod, Box 114
= 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;
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
Radiolubitel # 9, 1992,