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You didn't say how do you imagine the boom loaded and how you intend to =
feed it.=20
Probably you meant using the boom as a dipole, already utilyzing the =
capacitive loading of yagi's elements, and finally tuning with other =
loading coils and whips at the edges of the boom.=20
The same probably, you imagined boom antenna will be center fed with a =
gamma or a T match.=20
=20
If the above is your plan, it looks quite a complex job to realize.
=20
Generally speaking the first action will be to make such an antenna =
mechanical center also its electrical center. (the boom to mast area =
must become the antenna center, in other words)
This implies to make a short electrical joint between shield of TH11 =
line and the boom to mast area.
Unuckily, apart this easy phisical joint, to effectively set as the =
highest antenna current that point,=20
the two legs (right and left) of the boom should now be loaded different =
one to the other.
Yagis elements of TH11, infact, are acting as capacitive loadings of the =
two legs of the "boom dipole" but since they aren't symmetrically spread =
along the boom and haven't the same lenght, also loading will have to be =
asimmetrical and compensative.
=20
Nothing is impossible, but such a work implies a big deal (computer =
modeling, measuring, experiments etc.) where knowdlege, time and efforts =
are needed at high levels but finally, the achieved antenna, a loaded =
dipole, can be much easier obtained by an extra dedicated dipole =
stacked over (or below) the yagi.
=20
=20
73,
Mauri I4JMY
=20
-----Messaggio originale-----
Da: Bob Thacker <k3gt@pgh.net>
A: Tower Talk <towertalk@contesting.com>
Data: mercoled=EC 19 maggio 1999 13.08
Oggetto: [TowerTalk] Loading Boom for 30 Meters
=20
=20
Posted this before with minimal response. Want to load the boom on a =
TH11 for 30, any suggestions?
=20
Thanks,
Bob K3GT
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<DIV><FONT size=3D2>You didn't say how do you imagine the boom loaded =
and how you=20
intend to feed it. </FONT></DIV>
<DIV><FONT size=3D2>Probably you meant using the boom as a dipole, =
already=20
utilyzing the capacitive loading of yagi's elements, and finally tuning=20
</FONT><FONT size=3D2>with other loading coils and whips at the edges of =
the boom.=20
</FONT></DIV>
<DIV><FONT size=3D2>The same probably, you imagined b</FONT><FONT =
size=3D2>oom=20
antenna will be </FONT><FONT size=3D2>center fed with a gamma or a T =
match.=20
</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>If the above is your plan, it looks quite a complex =
job to=20
realize.</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>Generally speaking the first action will be to make =
such an=20
antenna mechanical center also its electrical center</FONT><FONT =
size=3D2>. (the=20
boom to mast area must become the antenna center, in other =
words)</FONT></DIV>
<DIV><FONT size=3D2>This implies to make a short electrical joint =
between shield=20
of TH11 line and the boom to mast area.</FONT></DIV>
<DIV><FONT size=3D2>Unuckily, apart this easy phisical joint, to =
effectively set=20
as the highest antenna current that point, </FONT></DIV>
<DIV><FONT size=3D2>the two legs (right and left) </FONT><FONT =
size=3D2>of the boom=20
should now be loaded different one to the other.</FONT></DIV>
<DIV><FONT size=3D2>Yagis elements of TH11, infact, are acting as =
capacitive=20
loadings of the two legs of the "boom dipole" but since they=20
</FONT><FONT size=3D2>aren't symmetrically spread along the boom and =
haven't the=20
same lenght, also loading will have to be asimmetrical and=20
compensative.</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>Nothing is impossible, but such a work implies a big =
deal=20
(computer modeling, measuring, experiments etc.) where knowdlege, time =
and=20
efforts are needed at high levels but finally, the achieved antenna, a =
loaded=20
dipole, </FONT><FONT size=3D2>can be much easier obtained by =
</FONT><FONT=20
size=3D2>an extra dedicated dipole </FONT><FONT size=3D2>stacked over =
(or below) the=20
yagi.</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2></FONT><FONT color=3D#000000 =
size=3D2>73,</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2></FONT><FONT size=3D2>Mauri =
I4JMY</FONT></DIV>
<DIV><FONT size=3D2> </FONT></DIV>
<BLOCKQUOTE=20
style=3D"BORDER-LEFT: #000000 solid 2px; MARGIN-LEFT: 5px; PADDING-LEFT: =
5px">
<DIV><FONT face=3DArial size=3D2><B>-----Messaggio =
originale-----</B><BR><B>Da:=20
</B>Bob Thacker <<A=20
href=3D"mailto:k3gt@pgh.net";>k3gt@pgh.net</A>><BR><B>A: </B>Tower =
Talk=20
<<A=20
=
href=3D"mailto:towertalk@contesting.com";>towertalk@contesting.com</A>>=
<BR><B>Data:=20
</B>mercoledì 19 maggio 1999 13.08<BR><B>Oggetto: =
</B>[TowerTalk]=20
Loading Boom for 30 Meters<BR><BR></DIV></FONT>
<DIV><FONT color=3D#000000 size=3D2>Posted this before with minimal =
response.=20
Want to load the boom on a TH11 for 30, any =
suggestions?</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2></FONT> </DIV>
<DIV><FONT color=3D#000000 size=3D2>Thanks,</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2>Bob =
K3GT</FONT></DIV></BLOCKQUOTE></BODY></HTML>
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