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Re: [TowerTalk] 100ft 80meter Yagi

Subject: Re: [TowerTalk] 100ft 80meter Yagi
From: K4SAV <>
Date: Fri, 31 Mar 2006 19:10:58 -0600
List-post: <>
I notice the model uses 2 inch diameter elements throught out, which 
can't be correct. What it the taper schedule for the elements?

Jerry. K4SAV

denis coolican wrote:

>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 one.
>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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