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[TowerTalk] 80m LPDA that works

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Subject: [TowerTalk] 80m LPDA that works
From: (Terry Mitchell)
Date: Tue, 16 Dec 1997 20:10:47 -0800
Please find following messages received since I reported that no one could
make the 80m LPDA work. N4ZC in NC has a few currently in use and is very
happy with them.
Terry, VE7TLL on NA051 'the Misty Isles'

> From:
> To:
> Cc:
> Subject: Re: Fw: 80m wire antenna ideas?
To: <>
> Date: December 16, 1997 10:07 AM
>Hello Terry,
I don't get tower talk but N4KG sent me a copy of your message since I do
use some wire 80m LP antennas. I have never found anyone that could make
one as listed in the QST article/antenna book to work.

I think the problem is the height above ground.  You've just got to get
them higher than they show them. I'm a retired radio op from  the USCG
and we used a number of wire LP antennas that worked VERY WELL. The
answer is that they started from 150' towers and went down to a 20' tower
way out in front.....but, the lowest part of the wires was still over 60'

When I put my first one up here, I ran it between 2 towers@45' for a
test. SWR was crazy and didn't really work that well. The towers are 120'
and 130', so 45' was just a starting test. I then took it up to about
65'......the SWR came down and the antenna was better than my 100' high
ref dipole. I next took it to 110' and it was a REAL WINNER. That one was
pointed NE for Europe/mid east/n africa. It worked so VERY WELL, I put up
another pointed W for the pacific. Another GREAT antenna. It ran from the
130' tower, with a rope off the front, over a 500' open field to a tree.
That made the lowest part of that LP about 85'

I think it was about 1987 I used those two LPs and a dipole to make #2 in
the US in the ARRL DX contest, single-band 80. A W1 beat me but they
start running 
Europeans an hour and a half before we start hearing them down here. I'm
in western NC which is as far west as Ohio, not really an east coast
location. My score for that contest is still the record for W4 land
single band 80 in the ARRL DX test.

I've since added a 3rd LP pointing S. Another WINNER. This one goes from
my 100' tower to a big oak tree. Yes, it helps to have a number of high
towers. I've got 130' 120' 110' 75' and 75' towers.

I had 146 countries on 80 before I put up these LPs.....I'm up to 287 on
80 now. As with any low horizontal antenna, they don't work worth a damn
when they're low. If you can get ALL the wire above 60' I think you would
be happy.

By the way, I don't use the design as shown in the antenna book. There
were some great articles in the old Ham radio magazine back in the late
70s/early 80s, showing truncated wire LPs that didn't use such a small
taper factor. They used .845 to go from 149' to 90'. I used .91 and went
from 142' to 107'.....this gives more gain and still gives below 1.5:1
SWR from 3.5 to 4 mhz.

By the way, I've also tried 500' V beams, phased delta loops and
parasitic delta loops,  a half wave sloper system, 1/4 wave slopers, and
wire yagi antennas on 80. The wire yagi@100' was very good, but won't
cover both phone and cw parts of the band....that's why I went to the LP

I wish my towers were higher so I could try the wire LP on 160 but I
don't feel they are high enough to really do the job on that band. If you
get QST, you may have seen the May 97 issue which shows what I do on that
band with a balloon vertical. Since that article, I've added a short 30'
tower for the elevated radial system for the balloon vertical.

Well, this may be more than you needed, or wanted, but thought I'd let
you know that my LPs work really great for me.
73 Roger N4ZC
> Terry,
> First, I'm NOT an antenna expert, I've just put up a number of 'em.
> Now, some things from the antenna book that you can use.  Their idea of
> using ropes between element ends so you only have to use 4 corner ropes
> is a good idea. My first used ropes off each element which uses a lot
> more rope. I've since changed the first one to just the 4 corner ropes.
> This also makes it more easy to keep all alements in the same plane. I
> also used their ideas for the open wire feeder and spacers to feed each
> element.
> If you build one of these, I sure woudn't use copper-clad steel wire like
> I did with the first one....god what  pain in the ass trying to keep the
> wire from kinking., It's just too much wire to have that worry. I used
> some wire I got from the wireman called "silky". You can role it out on
> the ground and forget it. No worry about it trying to coil back up on
> itself.
> Another thing to keep in mind is not to put element tension on the
> open-wire feeder or the crossover wires that give the 180 deg phase shift
> from element to element. Wrap the element wire around the center spacer.
> DON'T just go thru the hole and make the cross over as one continuous
> wire without going thru the hole again to take the tension off the
> crossover. Over time, the tension will pull the cross over wire down into
> the open-wire feeder, shorting it out.
> They show the elements swept forward like TV LP antennas. They were
> wrong. They mixed apples and oranges there. TV antennas are swept forward
> like that becaue they are using the elements in a harmonic length fashen
> which does indeed give more gain that way....but the way they are used in
> this article, they are half wave elements and you don't get more gain by
> sweeping them forward like that.
> Gain comes much more slowly per given boom length on the LP than say a
> YAGI. You get about 3 db more gain when you double the YAGI boom
> length...not so with the LP.
> But of course the YAGI won't cover the CW/SSB parts of the band like the
> LP.
> I use .93 taper .08 space factors on my 60 deg and 270 deg LPs and .91
> taper .08 space factor on the S LP.  The orginal used the .91 .08 and
> worked very well. When I rebuilt it and at the same time put up the new W
> LP I decided to go for a bit more gain andc went with the .93 taper. It
> covers the band OK from 3.5 to 3.9 mhz but starts to climb when you get
> much above 3850, so when I put up a 180 deg LP I went back to the .91
> taper to cover the band all the way up to 4 mhz. I don't go up there
> myself, but some guys use my station in the SS contest and it's nice to
> be able to go any place in the band during a domestic contest like that.
> One of the nice things about the LP is once you decide on the taper
> factor, the element lengths stay the same, no matter what space factgor
> you use. So, once you decide how much of the band you want to cover, you
> then look at how much space you have to decide the space factor and how
> long you want the beam to be. While you have space for an optimum spaced
> LP, I think I'd look at putting up two, back to back shorter LPs to cover
> 2 directions. I can design them to and boom length you want, but here are
> a few examples
> .93 taper
> 142'  132' 1" 122'10" 114'
> .05   .08     .10     .17
> 14'2" 22'9"   28'5"   48'3"
> 13'2" 21'1"   26'5"   44'11"
> 12'3" 19'8"   24'6"   41'9'
> .91 taper
> 142'  129'3"  117'7"  107'
> .05   .08     .1      .17
> 14'2" 22'9"   28'5"   48'3"
> 12'11"        20'8"   25'10"  43'11"
> 11'0" 18'10"  23'2"   40'
> There is only about 1.5 db more gain with the optimum .17 over the short
> .05
> space factor. LP gain comes faster with more taper factor than more space
> factor.
> Going from .91 to .95 taper would give the same amount of extra gain, but
> at the cost of more elements or less band coverage.
> More elements would allow a higher taper factor with more gain and still
> cover the whole 3.5 to 4 mhz band. If you wish to use a higher taper
> factor for more gain, I'll be happy to give you the info for any size LP
> you would like to try. It would take 5 el for .93, 6 el for .94 and 7 el
> for .95 to cover the whole 3.5 to 4 mhz band. Well, I guess I should also
> say that if you are willing to give up a bit of front-to-back at the CW
> end of the band, you could start with a back  element of of say 138'
> which would allow one less element for each taper factor. If you don't
> work any CW, I could shorten it even more to cover just the phone band. I
> guess I should have first asked you if you work CW.  I can come up with
> any size you want to cover the band you want to operate.
> 73 Roger

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