[Lowfer] construction details

[Eric KD5UWL]

Hi,

I've been asked by a couple to post here the details of the construction 
of the antenna in the picture I sent to Dex's LowFER antenna page.

Please don't believe that I think that what is presented here is The Way 
to do it, or even a very good idea.  In fact, I'm sure many of you will 
find serious flaws in the design, and I'm aware of a couple of those flaws 
myself...and was aware of them even as I built it.  Some of the methods 
will be considered highly temporary or downright ill advised and maybe 
even entertaining <g>

But this is what I have, and all UWL LowFER and XFX signals were 
transmitted with it.  I was asked to post complete details so that's what 
I've tried to do here.  Sorry so lengthy.

The mast consists of 3 x 10' sections of 3" ID DWV PVC.  About 2'+ is 
below ground level -- so, including the couplings, the overall height is 
probably really only about 28'.

The wire that is the vertical element is #12 stranded Cu THHN.  I began 
with 22 gauge solid hook-up wire, but the feather weight of this wire 
combined with too few zip ties made it vibrate too much in the stiff winds 
of last March.  So I took it down, replaced that wire with the #12, and 
used many more zip ties ... one about every 18" or so.  All zip ties 
mentioned here are the black UV resistant type.

The tiny capacitance hat uses as a hub a PVC "closet flange" ... normally 
these are used to secure a toilet to the floor.  For radials I bought 2 x 
8' x 5/16" solid Al rods.  I drilled 1/16" holes through these rods at the 
hub and then every 1' out to the end of the rods.  I secured the first rod 
to the hub by running several loops of stainless steel "safety wire" (used 
for securing nuts and bolts in the aviation industry, I think) through the 
1/16" holes and through the holes in the edge of the flange.  The second 
rod crosses the first rod at right angles.  It is supported at the edges 
of the flange with hardwood dowels that are protected by spar urethane.  
You see, the first rod lays flat against the flange and is secured there 
as described.  But the second rod cannot lay flat against the flange 
because the first one is in the way.  So the dowels (about 4" in length) 
are at the edge of the flange and parallel to the first rod, one on either 
side.  They are slightly larger in dia than the rods and are secured with 
the safety wire and zip ties.  This gives the second rod solid support and 
the two 8' rods now appear as 4 x 4' radials.

This particular closet flange has a center knockout which I left in as a 
plug.

Where the rods cross they are connected with bare solid hook up wire 
looped many turns around the intersection and tightly so.

Additional hook-up wire was stripped and run through the holes that are 
spaced every 1' through the rods.  SO I have 4 concentric "rings" 
(squares, really) spaced a foot apart around the hub.  This makes a halo 
around the outside, but also one a foot inward, and then another, and 
another.

These bare wires are all connected together with more bare wire, and 
everything is soldered, of course.  

The #12 ends about 2' below the tophat, and then 4 bare hookup wires serve 
as the upleads, one each connecting to each of the four quadrants of the 
tophat.

The loading coil is on an 8" piece of PVC I found next to the road and 
wound with approx 26 gauge genuine Ma Bell frame wire:  
http://www.nutstreet.net/images/lowfer/20030322-004.jpg
This is about 7.8mH (calculated).  The clipleads you see in the picture 
were used on the first day and all these connections have been redone with 
most all soldered.

The 3 guys are 1/8" 60# swl polyester.  Each end terminates in black 
electric fence insulators which are connected to the flange 
with multiple loops of the stainless steel safety wire.  The lower end of 
the guys have the same insulator setup and the safety wire on this end is 
looped several turns through stainless eye bolts which are screwed into 
pressure treated fence posts.

This antenna is attached to the house at the eve (I know this is wrong and 
having it anywhere near anything is bad) with steel strap like compacted 
boxes are often secured to pallets with.  I got it into the air by waiting 
for utter darkness and then walking it up while my wife held one of the 
guy lines.  The lower end was directed into a 2' deep post hole (below the 
eve - about 18" out from the wall) by cider blocks placed next to the 
house.  As I walked toward the house raising the mast as I went the bottom 
tried to slide toward the wall but couldn't because of the cinder blocks.  
Once it reached vertical I directed it fully into the hole, ran up a short 
ladder to attach the strap to the eve, and then tied down/adjusted all the 
guys.  

This has proved solid (but it's only been a year) in very strong winds, 
storm fronts, etc.  As Charlie KC0EH will attest, the wind here can be a 
real test.  There is nothing to slow the wind between here and North 
Dakota except for a barbed wire fence fabled to be up somehwhere in Nebraska ...
but it's usually down.

It is coming down very soon to make way for the new XFX flattop which will 
actually be much further out in the yard but the vertical is coming down 
anyway.  It was solid this year but I don't know if it would have lasted 
much longer (although from the ground I don't see any signs of failure, 
even in high winds) -- it was done as cheaply as I could think to do it 
and I never thought of it as lasting for a long time.  For example, 
how long could the wood dowels have been expected to last up there in 
the sun and rain?  With the urethane ... a very few years *maybe*, but 
not much longer I wouldn't think.  When I take it down I'll inspect the 
top and see how it held up.

Eric