Glenn,
I put up an XM-240 here in NH just over a year
ago. Before I did I checked with the local
contest club guys to see what things I might be
careful about. Here?s what I did ?
Replaced the boom to mast plate with a larger
plate to accommodate 4 DX engineering saddle
clamps to keep it from twisting on the mast. The
OEM plate has just 2 muffler clamps sized for 2 ½
? mast.
Replaced the oem balun with a balun rated for
1500W key down, several folks had seen the oem
balun fail running RTTY at full power
I used locktite on the small fasteners on the
capacitance elements as the nylon insert nuts on
fasteners that small provide insufficient grip to
prevent loosening
I made a few other hardware substitution mainly to
replace zinc coated steel with stainless etc.
After it was up for just a month I had a failure
of one of the U channels that holds the elements
to the boom. The wind force ( minor NH storm,
gusts of 40 ? 50 MPH for several hours ) caused
the ¼? hex bolt heads to tear trough the U
channel. When it failed I called the manufacturer
and they sent me a replacement channel. After
doing some research I found that the new owners of
the Cushcraft product line had made a substitution
from the original design. The original design
used an extruded, heat treated aluminum U channel
but the substituted piece was made from 1/8? sheet
in a brake, apparently not heat treated. The
original would have been much stronger. My fix
was to replace the u channel and install large
stainless steel fender washers on the ¼? bolts to
spread the force out over a larger area. It was
the quickest fix at the time. If I had it to do
over I would have used heat treated aluminum
channels ¼? thick. So far the band aid fix is
holding up though.
One thing I can say that the manufacturer has
apparently improved on is that they now seal the
loading coils in an epoxy-like substance that
looks to solve the problem of the old design that
used heat shrink tubing that allowed the
connections to corrode.
If you are interested I can send you a spread
sheet of the issues I was concerned about showing
the likely cause and my fix. I also have photos
of the failed U channel.
Dale AA1QD
Message: 5
Date: Fri, 14 Mar 2014 22:49:15 -0600
From: Glenn Pritchard <hfcomnet@gmail.com>
To: towertalk@contesting.com
Subject: [TowerTalk] Discoverer 7-2 or Cushcraft
xm-240
Message-ID:
<CABS66GkKUS673fFx27HoCUpoKDZFDWJs_FCKk_xG_YB82EA6
mw@mail.gmail.com>
Content-Type: text/plain; charset=ISO-8859-1
Hi guys
Have been pondering this over for a couple of
months.
In the past my monobander for 40 has been KLM,
however it's time to replace
this antenna and currently the antenna is down.
Question is, which of the two 40 meter yagis has
the better track record?
I have never seen the hy-gain up close but the
performance was pretty good
for a linear loaded system and the gov't had them
for monitoring stations
in Canada.
As for the xm240, not sure.
Just looking for some input from those that may
have experience with either
of these antennas.
Tnx,
Glenn, VE6ND
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