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<H1>Revolutionary Yagi Antenna Feed System </H1>
<P><FONT face=Verdana><STRONG>Justin Johnson G0KSC</STRONG>, says that he has
pioneered a revolutionary new feed system for the Yagi directional beam antenna,
which will see it's Debut in the next issue of <STRONG>DUBUS</STRONG> - the
serious magazine for VHF and up amateur radio </FONT><A
href="http://www.dubus.org/" target=_blank><FONT
face=Verdana>www.dubus.org</FONT></A><FONT face=Verdana>.</FONT></P>
<P><FONT face=Verdana>Justin writes:</FONT></P>
<P><FONT face=Verdana>Whilst there are many benefits seen with the new system,
the most important break-through is the suppression of the age old problem of
unwanted side lobes within longer Yagi designs.</FONT></P>
<P><FONT face=Verdana>The feed system (which does not consist of a dipole and
no, it is not a Quagi!) has 2 different feed points. Whilst the antenna needs
re-modeling in order to change from one to the other, different characteristics
are seen from each method. The first enhances the bandwidth capabilities of the
Yagi and presents never-seen-before ultra low return loss, excellent gain and
front to back ratio, whilst the other provides more traditional OWA (Optimised
Wide-band array) style bandwidth with good improvements in forward gain and
massive improvements in front to back ratio.</FONT></P>
<P><STRONG><FONT face=Verdana>What people say</FONT></STRONG></P>
<P><FONT face=Verdana><EM><STRONG>'This could be a turning point in the
development of the Yagi Antenna'</STRONG></EM> <BR>Popa, YU7EF - World renowned
Yagi antenna designer/engineer - </FONT><A href="http://www.yu7ef.com/"
target=_blank><FONT face=Verdana>www.yu7ef.com</FONT></A></P>
<P><FONT face=Verdana><EM><STRONG>'Justin, Indeed this looks like a unique and
winning design!'</STRONG></EM> Joel R. Hallas, W1ZR - Technical Editor, QST
Magazine</FONT></P>
<P><FONT face=Verdana><EM><STRONG>'Hi Justin, Many thanks for the plots, these
diagrams look really beautiful! I have never seen such F/B and low sidelobes for
a Yagi before'</STRONG></EM> <BR>Joe CT1HZE - DUBUS Magazine</FONT></P>
<P><STRONG><FONT face=Verdana>Benefits of the new design</FONT></STRONG></P>
<P><FONT face=Verdana>Whilst going to press, experiments are still being
conducted with the new Yagi. However, the new feed adds a number of very
interesting characteristics to the Yagi which when focus is applied to
optimisation, excellent not-seen-before Yagi performance is the result. The list
so far consists of the following:</FONT></P>
<P><FONT face=Verdana><STRONG>* Superior Front to Back Ratio with very high
suppression of unwanted lobes</STRONG></FONT></P>
<P><FONT face=Verdana><STRONG>* Extended/alteration of ‘ideal’ boom
length</STRONG></FONT></P>
<P><FONT face=Verdana><STRONG>* Exceptional clean pattern
performance</STRONG></FONT></P>
<P><FONT face=Verdana><STRONG>* Ultra-wideband
characteristics</STRONG></FONT></P>
<P><FONT face=Verdana><STRONG>* 50 Ohm impedance – no matching
required</STRONG></FONT></P>
<P><FONT face=Verdana><STRONG>* Easy fine-tuning of feed arrangement
itself</STRONG> </FONT></P>
<P><FONT face=Verdana>More information and plots at: </FONT><A
href="http://www.g0ksc.co.uk/latest-design.html" target=_blank><FONT
face=Verdana>http://www.g0ksc.co.uk/latest-design.html</FONT></A></P>
<DIV class="img_caption " style="WIDTH: 719px"><IMG class=caption
title="a 10el 144Mhz high gain, low loss Yagi with the new feed system"
src="http://www.g0ksc.co.uk/images/stories/ALFA/swr1.jpg" border=0
$included="null">
<P>a 10el 144Mhz high gain, low loss Yagi with the new feed
system</P></DIV><SPAN style="FONT-SIZE: 10pt; FONT-FAMILY: Tahoma"><BR></SPAN>
<P></P>
<P class=MsoNormal><STRONG><SPAN style="FONT-SIZE: 10pt; FONT-FAMILY: Tahoma">50
Ohm impedance, no matching unit required</SPAN></STRONG></P>
<P class=MsoNormal><STRONG><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Tahoma"></SPAN></STRONG> </P>
<P class=MsoNormal><SPAN style="FONT-SIZE: 10pt; FONT-FAMILY: Tahoma">As with
all of my designs which keep the amateur antenna builder, novice or professional
in mind, no matching unit, coaxial stubs or any other tuning arrangement needs
to be added to the antenna. A simple 1:1 balun or coaxial choke balun at the
feed point is enough. As stated above, direct feed of the antenna is possible
and due to the design of the feed system itself, fine tuning can be achieved
easily.<STRONG> Full details in DUBUS! www.dubus.org</STRONG></SPAN></P>
<P class=MsoNormal>Some plots of Yagis created so far:</P>
<P class=MsoNormal> </P>
<DIV class="img_caption " style="WIDTH: 507px"><IMG class=caption
title="A 9el 50Mhz G0KSC Yagi - How clean is that pattern!"
src="http://www.g0ksc.co.uk/images/stories/ALFA/9el6az.jpg" border=0
$included="null">
<P>A 9el 50Mhz G0KSC Yagi - How clean is that pattern!</P></DIV>
<P></P>
<P class=MsoNormal> </P>
<P class=MsoNormal></P>
<DIV class="img_caption " style="WIDTH: 507px"><IMG class=caption
title="Even the elevation pattern is looking good"
src="http://www.g0ksc.co.uk/images/stories/ALFA/9el6elvation.jpg" border=0
$included="null">
<P>Even the elevation pattern is looking good</P></DIV>
<P></P>
<P class=MsoNormal> </P>
<P class=MsoNormal></P>
<DIV class="img_caption " style="WIDTH: 572px"><IMG class=caption
title="Ultra low return loss to go with the flat SWR"
src="http://www.g0ksc.co.uk/images/stories/ALFA/fd0609dswr.png" border=0
$included="null">
<P>Ultra low return loss to go with the flat SWR</P></DIV>
<P></P>
<P class=MsoNormal> </P>
<P class=MsoNormal></P>
<DIV class="img_caption " style="WIDTH: 572px"><IMG class=caption
title="Fantastic front to back not seen with no unwanted forward lobes before"
src="http://www.g0ksc.co.uk/images/stories/ALFA/fd0609dgain.png" border=0
$included="null">
<P>Fantastic front to back not seen with no unwanted forward lobes
before</P></DIV>
<P></P>
<P class=MsoNormal> </P>
<P class=MsoNormal></P>
<DIV class="img_caption " style="WIDTH: 572px"><IMG class=caption
title="Nice near 50 Ohm impedance too"
src="http://www.g0ksc.co.uk/images/stories/ALFA/fd0609dimp.png" border=0
$included="null">
<P>Nice near 50 Ohm impedance too</P></DIV>
<P></P>
<P class=MsoNormal> </P>
<P class=MsoNormal>A preview of the 11el 144Mhz Yagi to be featured in DUBUS
below:</P>
<P class=MsoNormal> </P>
<P class=MsoNormal><IMG
src="http://www.g0ksc.co.uk/images/stories/ALFA/11el144az.jpg" border=0> </P>
<P class=MsoNormal> </P>
<P class=MsoNormal><IMG
src="http://www.g0ksc.co.uk/images/stories/ALFA/fd14411uswr.png" border=0></P>
<P class=MsoNormal> </P>
<P class=MsoNormal></P>
<DIV class="img_caption " style="WIDTH: 491px"><IMG class=caption
title="8el on 50Mhz with very high F/B and no lobes"
src="http://www.g0ksc.co.uk/images/stories/ALFA/az.jpg" border=0
$included="null">
<P>8el on 50Mhz with very high F/B and no lobes</P></DIV>
<P></P>
<P class=MsoNormal> </P>
<P class=MsoNormal></P>
<DIV class="img_caption " style="WIDTH: 491px"><IMG class=caption
title="10el for 144Mhz, a nice clean pattern"
src="http://www.g0ksc.co.uk/images/stories/ALFA/az10144.jpg" border=0
$included="null">
<P>10el for 144Mhz, a nice clean pattern</P></DIV>
<P></P>
<P class=MsoNormal> </P>
<P class=MsoNormal></P>
<DIV class="img_caption " style="WIDTH: 491px"><IMG class=caption
title="Ever seen a pattern like this from a 5el 50Mhz Yagi?"
src="http://www.g0ksc.co.uk/images/stories/ALFA/az65.jpg" border=0
$included="null">
<P>Ever seen a pattern like this from a 5el 50Mhz Yagi?</P></DIV>
<P></P>
<P class=MsoNormal> </P>
<P class=MsoNormal></P>
<DIV class="img_caption " style="WIDTH: 491px"><IMG class=caption
title="The 5el Yagi for 50Mhz looks good elivation wise too"
src="http://www.g0ksc.co.uk/images/stories/ALFA/el65.jpg" border=0
$included="null">
<P>The 5el Yagi for 50Mhz looks good elivation wise too</P></DIV>
<P></P>
<P class=MsoNormal> </P>
<P class=MsoNormal><STRONG>Visit www.DUBUS.org for details of the next issue
release date.</STRONG></P>
<P class=MsoNormal>73</P>
<P class=MsoNormal> </P>
<P class=MsoNormal>Justin G0KSC </P></DIV></BODY></HTML>