On my CL-33 the braid of the coax btw. the corresponding site of the driven
element is NOT bonded to the boom nor is such mentioned in the manual.
73
Peter
-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of Jim
Thomson
Sent: Montag, 15. Dezember 2014 04:12
To: towertalk@contesting.com
Subject: [TowerTalk] An alternate yagi feed method
After perusing through the Mosley.... tech notes, I see they use this
alternate feed method on their
various yagis. DE is split in the middle, and each DE ele half is insulated
from the boom.
They wire the center conductor of the coax to one side....and the braid to
the other half.
They then bond the DE ele half..that has the braid, to the boom ! Then no
requirement for a balun,
and no pesky CM current flow anywhere. Pattern is not affected. At 1st
glance, it appears they
have an unbalanced DE... fed with coax. Will this actually work ? A few
weeks ago, I had previously
drawn the exact identical config on paper...and wondered why it had never
been written about in
any book. I figured it must be fubar, but was still tempted to at least try
it. Apparently Im 60 years too
late, and am just re-inventing the wheel. Is Mosley out to lunch with their
feed system ?
To make the DE 50 ohms, Mosely resonates the DE at a lot lower freq than
normal... to increase the feed point Z.
This of course creates XL. The XL is tuned out with a series cap in each
half of the DE, where the ele is split in the
middle. Very similar concept to a .375 wave vertical, or inverted L on
160m. Mosley uses a short length of insulated
wire inside each ele to provide the series C.
Jim VE7RF
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