One added note,
In the case of the broken element I'd not use the doubler to repair the
broken element, but rather make a new element, add the double, epoxy the
doubler in place and let cure, foam the inside of the tube, let cure,
and then drill the hole using a centering guide. The foam will actually
add measurable strength to the element in addition to the doubler.
73
Roger (K8RI)
Roger (K8RI) wrote:
> RLVZ@aol.com wrote:
>
>>
>> Hi Doung & all,
>>
>> In my original post, I stated that some of my "X-Hat rods were falling
>> off" so I'd like to lengthen the element and eliminate the X-Hat rods.
>>
>> A better description would have been I've had some "X-Hat rods breaking
>> off". I had the new XM-240 in the air for less than a month and one X-Hat
>> rod broke in two and fell to the ground. I dropped the antenna and
>> replaced
>> the broken X-Hat and put the antenna back up. Within another month I had
>> another broken rod. Each time the rod broke in the middle where the hole
>> is
>> drilled thru the center casting.
>>
> I'd at least try what we do with aircraft in areas like that...Use what
> is called a doubler. find a piece of rigid aluminum that will just fit
> inside (or outside) of these elements. Redrill the hole so the inside
> and outside ones match. A centering jig that allows holes to be drilled
> through the *center* of the doubler and at *right angles* to the element
> would probably be a good idea. I don't know the length of the pieces
> that are breaking in two, or the size of said element top hats. The
> length of the doubler is some what dependent on the size and length of
> that top hat, but if it's a 1/4" then I'd want at least a 6" doubler. If
> it's a 1/2" then maybe 8" but I'd need to know how long the element tops
> hats are to come up with an estimate there.
>
> At-any-rate, once the doubler is drilled and fitted so it easily slips
> over the element or inside (my preference is outside) then put a light
> coat of epoxy on the mating surfaces and slide the two together making
> sure the holes line up. Once cured it should never break.
>
> Another route would be to fill the top hat tubes full of the good
> expandable foam that doesn't form large bubbles or expand into rigid
> foam that will warp door and window frames. It will weight little, but
> dampen any vibration and is far better than using nylon rope like we
> used to do.
>
>> After losing a single X-Hat rod the
>> resonant frequency jumped aprx. 200 khz making the antenna unusable on the
>> CW
>> portion of the band without a tuner. By the way, I did use the antenna
>> with
>> a tuner on the CW portion of the band and now my Cushcraft Balun has a
>> burn mark on it and it's warped!
>>
>>
>>
> That's a sign of a marginal balun.
>
>> I do not know what is causing my X-Hat Rods to break off. Perhaps the
>> rods center casting material was defective.
>>
> Center casting material? Is there some where I could find a photo or
> drawing of this part?
>
>> But more likely it's the large
>> birds landing on my antennas including Ospreys and Owls... perhaps they are
>> flying into the X-Hats?
>>
>>
> I've never seen them fly into something like that but they certainly
> will roost on them if they are any where near level. Cormorants busted
> the boom truss on my 7L C3i 6-meter Yagi.
>
>>
>> So I'd love to eliminate the X-Hat if possible.
>>
>>
>>
> You can make the element longer but the bandwidth will probably be
> narrower than the original design.
>
> 73 and good luck,
>
> Roger (K8RI)
>
>> 73,
>> Dick- K9OM
>>
>>
>> In a message dated 2/8/2010 9:35:04 PM Eastern Standard Time,
>> ve5ra@sasktel.net writes:
>>
>> X hat rods falling off - that is unusual. I've had my XM240 up for
>> years and never have the rods fallen off. I installed them as per CC.
>> So what is causing your rods to fall off or do you mean breaking off?
>>
>> Doug
>>
>> I'll run the race and I will never be the same again.
>>
>> -----Original Message-----
>> From: towertalk-bounces@contesting.com
>> [mailto:towertalk-bounces@contesting.com] On Behalf Of RLVZ@aol.com
>> Sent: February 8, 2010 4:44 PM
>> To: towertalk@contesting.com
>> Subject: [TowerTalk] XM-240 Shorty-Forty: X-Hat Modification
>>
>> Hi Guys,
>>
>> I've had problems with the X-Hat Rods falling off of my XM-240.
>> Therefore, I would like to eliminate the X-Hat by lengthening the
>> elements. I'm
>> wondering if anyone has done this successfully and how much length must
>> be
>> added to the elements?
>>
>> Or if anyone has modeled the removal the XM-240 X-Hat by lengthening the
>>
>> elements... please share what element lengths you came up with.
>>
>> Thanks!
>>
>> Dick- K9OM
>> _______________________________________________
>>
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