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Sent: Saturday, March 15, 2014 10:00 AM
Subject: TowerTalk Digest, Vol 135, Issue 15
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Today's Topics:
1. Re: Discoverer 7-2 or Cushcraft xm-240 (K4SAV)
2. Tower Base Challenge (Wilson)
3. Re: Discoverer 7-2 or Cushcraft xm-240 (D. Drake)
----------------------------------------------------------------------
Message: 1
Date: Sat, 15 Mar 2014 08:22:49 -0500
From: K4SAV <RadioIR@charter.net>
To: towertalk@contesting.com
Subject: Re: [TowerTalk] Discoverer 7-2 or Cushcraft xm-240
Message-ID: <53245429.4010704@charter.net>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Correcting a few things on the XM240 before putting it up would help.
Mine collected water inside the elements. The water ran down the X-hat
and into the hole used for mounting the X-hat. The plugs on the ends of
the elements served to keep the water inside. The loading coil is wound
on a hollow tube. That allows water to collect inside the loading coil
- not good at all. I plugged the hole at the X-hat, drilled some weep
holes and removed the element end caps. I did insert some stainless pot
scrubber material in the ends of the elements.
I also didn't like the sparks jumping from the reflector to the boom
when lightning was close, so I grounded the reflector to the boom. The
only thing that changes is the resonant frequency of the boom, which
could be a consideration for interaction with other antennas.
I think the boom to mast clamp could stand some improvement also.
Jerry, K4SAV
On 3/15/2014 7:39 AM, Wayne Kline wrote:
I have had Both of the antennas ...The hi Gain Dis-2 is a good antenna
the linear loading wires are problematic
if you live in a ICE area... I lost mine two times..... The Original
CD40 had a number of issues .
The XM240 is miles ahead of the original 2 element antenna. Mine has
been up two years and three heavy ice storms. The W6NL Maxon mod
improves an already good antenna
The weak spot on the XM240 is the boom to mast clamp... IMO I
re-drilled the plate for two High gain blocks
Wayne W3EA
Date: Sat, 15 Mar 2014 05:51:58 -0400
From: n1rj@roadrunner.com
To: towertalk@contesting.com
Subject: Re: [TowerTalk] Discoverer 7-2 or Cushcraft xm-240
My choice would be the XM-240 with the W6NL Moxon modifications.
Much better F/B and bandwidth.
73, Roger
On 3/15/2014 12:49 AM, Glenn Pritchard wrote:
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
_______________________________________________
------------------------------
Message: 2
Date: Sat, 15 Mar 2014 10:05:41 -0400
From: "Wilson" <infomet@embarqmail.com>
To: "towertalk" <towertalk@contesting.com>
Subject: [TowerTalk] Tower Base Challenge
Message-ID: <34C2AE4CD41546E1B1F3ECED71160007@WilsonPC>
Content-Type: text/plain; charset="UTF-8"
?If anyone wants to be serious about this, the formula for the pull-out
resistance of lag screws is on page 8-10 of this document
<http://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr190/chapter_08.pdf>.
Compare whatever numbers you get to the ultimate strength of 3/16 EHS
guy wire, factor in an appropriate safety factor, and I bet you'll
abandon the idea. ?
I read it and I see that even in pine, living or at least not rotting, a
thread penetration of 12X shank diameter will break a lag in tension.
Pretty amazing, really! So a half inch lag should be more than enough for
3/16 wire. But why depend upon pure tension when you can use a loop and
depend only upon the stump?
That said, the through bolt and big washer ?looks? a lot better and
doesn?t depend much on wood quality.
I don?t advocate using rotting stumps, but if one needs a temporary
solution a pine stump is fine for several years, all the more so if you
use a loop around it to anchor the wire. No, I?ve never done it, BUT I
regularly butt 6-8? stumps as hard as I dare with my 50HP tractor and it
has no effect except to shake me up and scratch the stump a little.
Generally, they can?t be uprooted by that method, but will eventually
break off after most of the wood has gone punky. I think most of them
retain lots of strength for at least five years, maybe longer. No doubt
there is some variation among the species, Some retain a strong heart
much longer than others.
WL
------------------------------
Message: 3
Date: Sat, 15 Mar 2014 10:22:00 -0400
From: "D. Drake" <daleaa1qd@gmail.com>
To: <towertalk@contesting.com>
Subject: Re: [TowerTalk] Discoverer 7-2 or Cushcraft xm-240
Message-ID: <000001cf4059$ef1c4cb0$cd54e610$@gmail.com>
Content-Type: text/plain; charset="iso-8859-1"
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 ?
? 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 ?? 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 ?? 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 ?? 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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