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[TowerTalk] 80M Delta loop

To: <towertalk@contesting.com>
Subject: [TowerTalk] 80M Delta loop
From: "Jon Casamajor" <k6el@comcast.net>
Reply-to: "Tower and HF antenna construction topics." <towertalk@contesting.com>
Date: Wed, 3 Feb 2010 19:06:11 -0800
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
All, 

Sorry my attempt at a graphic depiction of the 80m Loop I had run got so
hosed up with the formatting.  A little imagination will get you the point
and is probably better than me trying to re-do it. Hi hi

 

-----------------------------------------------snip>>>

 

Hi Stu,

I did exactly what you are describing several years ago.  I thought I had

documented the design but, darned if I can find it right now.  The antenna

was a full wave 80m delta loop cut for the low end of the band. I was

chasing 5BDXCC and CW was where I did most of my operating.  

The loop was pretty much equilateral with the apex at the top of my HDX-572

tower.  I make it fit, I tilted the loop out probably 10 to 15 degrees. I

used an Almond tree on one end and a 15' pole on the other end for support.

The base of the triangle was probably 12-15' above the ground.  I fed the

loop 1.4 wave down from the Apex on the left side looking at the loop from

the tower.

                              ______

                              |    /\

                              |   /  \    Not to scale but should

                              |  /    \   give you the picture. where X is
the feed point; 

                              | /      \   The loop was actually

                              |/        \  pretty much equilateral...diagram
isn't.

                              /          \

                             /            \

                            / |            \

         FEED POINT  -----X|                \

                          /___|_______________\ 

                              |

                              |

 

I used  a length of 75 Ohm RG11 I think it was to match the loop and at

3.505 it shows about 50 ohms  and 1.1:1 VSWR.  

I used this antenna on both cW and phone with a tuner for 75m. it was not at

all optimum on 75, but it would radiate pretty well. On CW this antenna was

an absolute killer and with my Henry 2K-3 I didn't wait in line too long in

pile ups.  This feed point will give you vertical polarization so it isn't

the best receiving antenna in noisy conditions and I often used my 2 el 40m

Yagi to listen to weak signals with pretty good success.

Getting one of these loops up and tuned takes some effort, I think I had to

whittle on the length 3 or 4 times but once you have it up and singing, you

will not regret the effort.  Mine, unfortunately came down in a wind storm

just a couple of years ago and I have never put it back up.  It helped me

get that 5BDXCC which was the mission.  The full wave loop is a real killer

if you can keep it up.  

I'm sure with a little research you can find the formula for the RG-11

matching stub. From memory it was in the neighborhood of 20 something feet

and I think the design was from one of the ON4UN articles.  Good luck, you

will love the loop on 80m!

 

 

Regards,

Jon Casamajor

 <mailto:k6el@comcast.net> k6el@comcast.net

 

"Politicians are like diapers...they both need changing often and for the
same reason"   Mark Twain.

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