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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