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
_______________________________________________
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|