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<p class=MsoNormal><font size=3 face="Times New Roman"><span lang=EN-GB
style='font-size:12.0pt'>2 element wire yagi for 80m band <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span lang=EN-GB
style='font-size:12.0pt'> <o:p></o:p></span></font></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span lang=EN-GB
style='font-size:12.0pt'>Wire antennas are easy and cheap to built. Many
amateur radio operators are using for low bands simple wire antennas that are
hanged too low to the ground. Radiation angle is 90 degrees, antenna is
radiating most of energy to the skies. This is the main reason why is their
perfomance decreased by many dB. <br>
<br>
There are two solutions: move antenna higher than actually is hanged or use
an other antenna. The first is hard to made. But try to take a think about
the second: the ARRL Antenna Handbook says in the chapter about two element
yagi antennas: the most powerful antennas. Adding only one element to the
dipole we got an advantage of lowering radiation angle, good feedpoint
impedance and directional radiation. <strong><b><font face="Times New Roman">We
have deigned a 2 element wire yagi for 80m band</font></b></strong> as an
answer for this request... <br>
<br>
We found an inspiration in the old magazine from 1986 „Yagi antenna for
3,5 MHz“. This design was simulated in the MMANA antenna software with
an excellent results. Main goal was an optimalization for heights from 10 to 20m
above ground. Here are answers:<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face=Symbol><span style='font-size:12.0pt;
font-family:Symbol'>·</span></font><span lang=EN-GB> antenna could be
optimized for <strong><b><font face="Times New Roman">direct feeding with a
50 ohm coax cable</font></b></strong><o:p></o:p></span></p>
<p class=MsoNormal><font size=3 face=Symbol><span style='font-size:12.0pt;
font-family:Symbol'>·</span></font><span lang=EN-GB> </span><font
face=Symbol><span style='font-family:Symbol'>·</span></font><span lang=EN-GB>
the resonant frequency is not depending on the height between 10 to 20m
height (only bit) <o:p></o:p></span></p>
<p class=MsoNormal><font size=3 face=Symbol><span style='font-size:12.0pt;
font-family:Symbol'>·</span></font><span lang=EN-GB> the impedance in the
feed point is decreasing with the height. For this antenna is an <strong><b><font
face="Times New Roman">optimal height above the ground 12 – 15m</font></b></strong>
<o:p></o:p></span></p>
<p class=MsoNormal><font size=3 face=Symbol><span style='font-size:12.0pt;
font-family:Symbol'>·</span></font><span lang=EN-GB> the bandwith for
SWR<2 is around 100kHz <o:p></o:p></span></p>
<p class=MsoNormal><font size=3 face=Symbol><span style='font-size:12.0pt;
font-family:Symbol'>·</span></font><span lang=EN-GB> <strong><b><font
face="Times New Roman">gain 9,1 dBi</font></b></strong>. F/B ratio is poor, 7
– 12 dB – depends on the antenna height <br>
The F/B ratio is poor due the fact that the distance between both elements is
small. It’s a compromise between antenna size, impedance and better F/B
ratio. <br>
<br>
The 2 element wire yagi was scaled for a SSB segment of 80m band. <strong><b><font
face="Times New Roman">The dipole radiator is 2x 20,03m and director is
38,07m, distance between elements is 7,74m</font></b></strong>. </span>Wire
thickness is 2mm. Feeding is through the balun 1:1. <o:p></o:p></p>
<p class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'><img width=519
height=274 id="_x0000_i1028" src="cid:image001.gif@01C876E5.534CA760"
alt="2 element wire yagi for 80m band"
title="2 element wire yagi for 80m band"><o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span lang=EN-GB
style='font-size:12.0pt'><br>
<strong><b><font face="Times New Roman">Construction details:</font></b></strong>
to do the 2 element wire yagi we need around 80m of wire, balun 1:1, four insulators
and some hanging ropes. I found very useful thin mountain ropes. <br>
<br>
Measure and cut the wires for both elements. Add 0,2m to the each side of
element for an insulator anchor. In the centre of radiator mount the 1:1
balun. Bound the distance and hanging ropes to the insulators. That’s
all. The 2 element wire yagi is needs four hanging points. That could be
trees in the garden or meadow. The advantage of close elements is that we
could two of them made on the house. <br>
<br>
<strong><b><font face="Times New Roman">The tunning should be not necessary</font></b></strong>.
In the height 10 to 15m should be SWR<1,3 (or lower). In heigher heights
improve the distance of elements otherwise will be the impedance too low.<o:p></o:p></span></font></p>
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