[TowerTalk] TowerTalk Digest, Vol 135, Issue 15

Sat Mar 15 18:09:28 EDT 2014

----- Original Message ----- 
From: <towertalk-request at contesting.com>
To: <towertalk at contesting.com>
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 at charter.net>
> To: towertalk at contesting.com
> Subject: Re: [TowerTalk] Discoverer 7-2 or Cushcraft xm-240
> Message-ID: <53245429.4010704 at 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 at roadrunner.com
>>> To: towertalk at 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 at embarqmail.com>
> To: "towertalk" <towertalk at contesting.com>
> Subject: [TowerTalk] Tower Base Challenge
> Message-ID: <34C2AE4CD41546E1B1F3ECED71160007 at 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 at gmail.com>
> To: <towertalk at 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 at gmail.com>
>
> To: towertalk at contesting.com
>
> Subject: [TowerTalk] Discoverer 7-2 or Cushcraft
> xm-240
>
> Message-ID:
>
>
> <CABS66GkKUS673fFx27HoCUpoKDZFDWJs_FCKk_xG_YB82EA6
> mw at 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
>
>
>
>
>
> ------------------------------
>
> Subject: Digest Footer
>
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> ------------------------------
>
> End of TowerTalk Digest, Vol 135, Issue 15
> ******************************************