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[TowerTalk] 80 meter yagis

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Subject: [TowerTalk] 80 meter yagis
From: (Rick Dougherty)
Date: Mon, 23 Jul 2001 07:25:17 -0400
Hello all...let me add a little more to the myth of 80 meter yagis...I have
a modified KLM way of explanation let me tell a little
history...this antenna origionally belonged to Steve K4JPD...he had it at
165 ft on a ridge line about 20 sw of Atlanta...with this antenna he was a
dominate force on 80m...he did have a little extra help from "eimac"
too...enuf said...this antenna came down when Hurricane Opel came inland
and tracked into middle Ga in "93 I think...Steve salvage enough to us it a
simply a dipole for a few months and after the insurance settled wit
him...he decided to sell all his towers and antennas and move to a new
location thta would not allow antennas...Steve called me and offered me the
dipole for $100...and if I would come up asap I could have the rest of the
crumpled antenna...

I took him up instantly...and drove to his qth asap...when I got there I
loaded the dipole and the rest of aluminum in my trailer and drove it
home...for the next 2 days I spent time laying out the full antenna on the didn't take long to see that the most important pieces were
there and with a small amount of fabrication I too could have a 2 element
yagi...well I had the resources to make it into a 3 element
nowcomes the delima....2 elements on a 36 ft boom?? or 3 elements on approx
a 60 foot boom...I was going to have to re-build the boom
friend W4EA had a version of Yagi optimizer and we ran the numbers for 2
elements and 3 elements...the gain is within 1.5 dbi and the only noticable
deiierence is some 8-10 dbi additional f/b ratio...the biggest difference
now becomes the physical windloading and keeping it in the air...Steve had
the antenna at 165 ft on Rohn 45 tower..he also had 4 or 5 more yagis on
the it was pretty loaded...the tower mainly failed due to the
high rains that came from the approaching Hurricane...the ground softened
and the wind pressure caused the guy anchor points to pull out of the
ground on the side from the approaching hurricane wind direction...(he had
also used mobile home screw in anchors) had he used proper anchors the
tower might still be there...

I guess one of the points that I am trying to make here is that this a lot
of load on a tower and it must be considered...I currently have the
re-built 2 element on a rohn 45 tower at 125 ft...this tower too is fairly
over loaded too...but it is over guyed too and has been up for the past 6
years and has survived another hurricane and 3 has 5 ele 20
at 96 ft fixed 5 el at 48 ft fixed and a 4 high 10m stack at 30 ft 60ft 90
ft and 120 ft...

currently I am building a second 2 el 80m yagi...have purchased 210 ft of
rohn 55 and will be installing 2 hi stack...this willl be with the lower
one at 105 ft and top at 210 ft...the top will rotate and the bottom will
be fixed to Eu...

The next point that I want to make is that just a single antenna will
dominate on the band nicely...ask Gary K4MQG...but rotors are also a
problem too...I have found that only a large Prop pitch or the Yaesu 2800
can hold this antenna...I have to point and leave it when I am away in the
direction of the prevailing wind....I still have the shear bolts snap at
least 2-3 times a you can see that this is not for the average requires lots of attention and care to keep it up...we
had a major ice storm 2 years ago and with my modifications to this antenna
no loss at all...the origional KLM design would have failed...

I still feel that in a major contest that I am not on the same playing
field with XX,LR,RM, and LPL when it comes to the numbers we get on 80m
versus their numbers...that is the difference in propagation and their
proximity to Europe...that is why I feel that the stack will help our
geography and level the field goes with out saying that beverages
are necessary to compliment this antenna too...currently my location
doesnot allow beverages...the new one will....

Yes the 80 antenna is a big big worry...but the satisfaction of operating
with make it worthwhile.....I think I remember and old FRC addage that "if
it didnt come down last winter, it wasn't big enough"

my 2 cents Rick nq4i

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