Before moving to my current location twenty-eight years ago, I put two
KLM-40-m dipoles on a sixteen-foot boom, built a feed-point match like
the Hy-Gain (?) 2-el forty of the time, and put it 10 feet below my
tribander at 45 feet. Kicked butt. No room for it here but I do survive
with a Hy-Tower. The 2-el forty now resides in my garage along with a
large Force-12 multi-el. Next time I move..., but do they work under ground?
Ah, point and shoot on 40 was fun.
73,
Joe Feustle, N8JF
On 1/28/2016 1:27 PM, Don W7WLL wrote:
Has been interesting to read the posts on this old antenna and the
various comments on how well or not they have worked for those who had
or have one.
I also have one. It is assembled, setting on some sawhorses out by the
tower and ready for remount with a TH7DX and A3WS on my HG-70HD tower.
My initial plan, after I get the rotator issue I have solved, is to
lower the A3WS a couple of feet and put the dipole at mast top, above
the A3WS.
Mine must be pre-40M-1 as all the literature that came with it just
calls it a KLM 7.2-1 DIPOLE ANTENNA.
When previously mounted in Portland on a TriEx WT-51, I never used a
truss nor do the instructions call for any. Even with the higher winds
we see here on the OR coast where we moved some years back, after
considering all the other two beams have gone through, I don't plan to
truss it (the TH7DX of course is trussed).
This is an interesting rotatable dipole design but does have a fairly
limited bandwidth. My recollection, for the settings I had, was that
it was close to 1:1 at the desired 7125 freq setting and ramped up to
about 2:1 at 7050 and 7200. Without a tuner it performed OK over the
whole band but at a lot higher SWR. It didn't perform any better than
a regular dipole except for the ability to rotate and maximize signals.
I don't know what the later 40M-1 manuals said, but mine even
discusses using the dipole vertically off a 20M or other beam, going
to far as to state that if mounted vertically with 'proper' spacing
from the tower that one might even get a little gain and F/B!!! Never
heard of anyone trying it and I remain dubious.
KLM also claimed that because of the 'specially designed linear
loading' that it should not cause any interaction with a 20M beam and
could even be mounted horizontally on its boom!!! I never heard of
anyone doing this either, but I have considered mounting it to the
mast below the TH7DX parallel with the elements (not the boom) just to
see what the results would be !!
The instructions also give some suggestions for other configured uses
of the element halves.
Along with my build and install instructions is a page which tells how
to convert another 7.2-1 dipole and turn the two into a 2-el 40M beam.
The sheet also provides instructions for getting the antenna to
operate in the 8.1 to 8.7 MHz area (say what????)
After KLM moved from CA to WA I assume that changed the nomenclature
to 40M-1 (?). I know they offered conversion kits in '96 (I have a
KLM retail price list) at roughly $300/element to create a 2, 3 or 4
el 40M beam using the original dipole. I also have a copy of a
dimensions sheet (with VSWR charts) and a list of parts for creating a
2 el. I don't know if was produced by KLM, but suspect so.
I looked for another KLM 40M rotatable dipole quite a while back, with
the thought then of building a 2-el, but never found one and dropped
the effort from my bucket list.
So, has anyone with one of these tried the 'different' mounting
methods KLM suggests and if so how did it turn out???
Don W7WLL
-----Original Message----- From: Arnie Pfingst
Sent: Wednesday, January 27, 2016 8:37 AM
To: towertalk@contesting.com
Subject: [TowerTalk] Klm 40m-1
I have a chance to buy a klm 40m1 rotatable dipole. The fella said its
on the ground. He said he "refurbished it" he has some paperwork for
it and a 5kw balun with it. My questions are, does this antenna need a
truss support and how do I put one on, was this antenna really
anything to write home about. How does it compare to say... the
cushcraft d40?Arnie
Sent via the Samsung Galaxy S®6 active, an AT&T 4G LTE smartphone
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