KLM 40

Howard Brainen hb@cpimaging.com
Wed, 5 Feb 1997 21:19:33 -0800


I've been trying to find the time to post my photos of the
mods on a web page...but real paying work seems to

Basically, I scrapped the KLM element to boom brackets.
The plastic inserts are fine for small beams, but worthless
for the big ones, especially with long elements and especially
on a hill.  I watched too many guys with KLM's on hillsides get
elements bent up over the top from winds coming up the hill.
The design is good for supporting the weight above the
brackets, but very weak when the forces come from below.

KW8N first gave me the idea, and K6ZM (now a silent key)
perfected it.  I use 1/4" aluminum angle, 4"x4" x 36" long
for element to boom.  They are hung under the boom with
stainless U bolts.  The element halves are attached to
the vertical side of the angle with similar U bolts and
PVC tubing for insulators.  The outer U bolts are
slightly higher than the inner ones, so the elements angle
up slightly as in the original design.  By hanging this
assembly under the boom, its protected from the elements
(i.e. rain) to a large extent.

On all my KLM antenna elements, I've replaced tubing clamps
with stainless machine screws and nylon lock nuts.  Simply drill
through both pieces where the element pieces overlap and
screw bolt them together.  They never come loose or vibrate
in the wind.  Do the same where linear loading straps connect
to tubing.  Put a machine screw and locknut through it and
it will stay put.

On the plastic spreader/insulators for the linear loading assemblies,
use several cable ties to keep them from moving.  When these
things vibrate in the wind they can knock the whole thing apart,
so I like to keep them stable.

I hate to take beams down for repair.  I prefer to think through
what could go wrong, prevent it in the first place and make it
stay up.  I only want to take it down to put up something bigger.
Lots of antennas are not designed very well from a mechanical
point of view and its obvious that the designers don't have to
climb towers and struggle with their antennas like we do.  I
applaud Force 12's use of rivets and, like my machine screw +
locknut solution, these should stay put.

Larry, W7CB has a 3 ele 40 KLM on his hillside near the California
coast.  He was constantly taking it down and repairing it until he
finally did these mods about 18 months ago.  Its still up and he's
beating me in 40M pileups!  Must be working.

73, Howard WZ6Z

> From: Don Daso <k4za@juno.com>
> To: hb@cpimaging.com
> Subject: Re: Tower Loading note
> Date: Thursday, February 06, 1997 12:47 AM
> Howard:
> I sure would be interested in hearing about some of the KLM 40M mods.
> We have (N4ZC & I) have one that's intermittent & driving us nuts.  We've
> taken it down & rebuilt it twice (no real mods since Rog living on
> retired USCG income & I was unemployed at the time...) & each time
> within a month this problem comes back.  We suspect the shorter of the
> two driven elements (the SWR just jumps up) but banging, twisting,
> turning or moving stuff while up in the air on the tower does nothing.  
> What have you done--if you can briefly decribe it?
> And wow...up in the air on the tower during a 'quake!  You California
> guys....
> vy 73 de Don K4ZA

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