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[TowerTalk] 100ft 80meter Yagi

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Subject: [TowerTalk] 100ft 80meter Yagi
From: "denis coolican" <>
Date: Fri, 31 Mar 2006 12:21:57 -0700
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I am planning on building an 80m yagi to cover the CW portion and hopefully 
retain good performance up into the phone band up to 3800.  I currently have a 
4 el OWA design on a 76' boom that covers approx 3650-3975.  It has been up for 
6 years and performs well, but not into the CW portion.  The new 80m yagi will 
not replace the one I have, but will be installed on a similar 150 foot tower.  
 I am planning to use a 100 foot tower that I have as a boom (40" triangular 
lattice structure)  with perhaps 5 full size elements as an OWA design if it 
has enough bandwidth.  I am not interested in loaded designs with relay 
switching.  The elements will be of the tapered pipe design, as is the current 

Denis VE6AQ designed and we both built a 40m yagi 5 element OWA design on a 59' 
boom that has wide bandwidth - about 400 khz - that if scaled would be  
adequate for 80m coverage.  That would require a 118 foot boom, but I am hoping 
I can squeeze it down to use the existing 100 boom that I have. It isn't 
impossible to add another 20 feet but I don't have the matching tower section 
to do that so would like to avoid that if possible.

As it correlates  to current towertalk threads, the tower will be guyed with 
multiple screw in anchors.  The guy wires (5/8 EHS) will be broken up with at 
least one insulator to reduce potential corrosion issues.  The rotor will be at 
the bottom of the tower and I will be using 4" IPS sked 40 black (4.5" OD water 
pipe with welded flanges) for the mast. I have used this on the current 80m 
yagi without any problems.   The mast near the top will be something 
significantly better.

Some design innovations that I have thinking about include:

      having the elements winched into place to allow for modification and 
repair by lowering them to the ground.

      having a heavy steel 4 sided "pyramid" shaped structure on the top of the 
mast.   A   matching structure will be built into the boom, so that the antenna 
can easily be lowered (by crane) over the self guiding structure and simply set 
in place without any critical placement issues.  It will be bolted down later 
for security.

Anyway, the main issue at hand is the electrical design not the physical.  I 
will have lots of time to ponder the mechanical aspects once it has been 
decided how much boom and how many elements are needed.
73 Don

A note from Denis Ve6aq 
I have modeled the 100 ft Yagi on EZNec and it can be downloaded from  The spacing between the DE and D1 is 
0.025 wavelength and I noticed that some of the modeling programs give 
inconsistent results at these close spacings.  I would like comments on the 
design and perhaps someone could run it on a NEC4 engine to see if the results 
are similar to what I have obtained. Comments would be appreciated.

Denis with Ve6Fi

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