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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