[TowerTalk] C31XR failure - ideas sought

[Mike Fatchett W0MU]

Did something happened that allowed the 15 driven to touch the boom?  
That would be about the only thing that would make it disappear.  Maybe 
the insulating material broke down?  Over head hitting the 15 element?

Yes the driven elements could touch each other in the wind.  I made a 
couple of spacers out of a non conductive material and placed one or two 
on either side of the boom.  Heck A piece of pvc and zip ties would work 
for a long while.

W0MU Mike

On 4/28/2024 8:25 PM, john at kk9a.com wrote:
> I have used a C31XR in Bonaire and the 15m SWR was not great but it worked.
> I believe elements can touch in the wind which really causes sudden high
> SWR.  I am not that familiar with the C31XR but I seem to recall bad 15m SWR
> being a common problem.  If it worked before perhaps you have a bad element
> connection however I have never seen that occur with any antenna, even in
> corrosive Aruba.  Does the C31XR have a hairpin that could have bent or
> broke?
>
> John KK9A
>
>
> Bill Ralston N7VM
> Hi all...
>
> I had a 15m failure on my C31XR.  It's not the usual initial challenges
> many have experienced, as this antenna was working correctly on all bands
> when originally installed years ago.  Nothing has changed with nearby
> antennas and installation, and the SWR curves look fine on 10m and 20m -
> just not seeing anything looking like resonance on 15m (no dips at all
> between 15-27 MHz).
>
>   For those not familiar with the older C31XR, this is in the single
> feedline, "open sleeve" feed arrangement.  The balun (current choke)
> connects at the 10m driver feedpoint, a close-spaced parallel wire
> transmission line extends a couple feet to the 20m driver feedpoint, and
> there is a matching coil across the 20m driver feedpoint.  The 15m meter
> driver is a few inches away from the 20m driver, but there is no direct
> electrical connection to the 10m & 20m drivers.  The 15m driver is shorted
> at its feedpoint by a short jumper.
>
> Visually, the elements all look fine, and I don't see anything wrong with
> the center jumper on the 15m driver nor the feed system / matching
> coil. The 10m and 20m SWR curves are fine, which also implies that the
> 10m-20m feed system is not the problem.
>
> Maybe the center jumper is open on the 15m driver (looks OK from the ground
> and seems unlikely). If the jumper is open, I'm not sure how that would
> affect the behavior, so I can't test that hypothesis from the ground
> (anyone know?).
>
> Another possibility is that a nested/riveted joint between tubing sections
> on the 15m driver isn't making contact, but that feels unlikely.  Has
> anyone ever had that problem before with a yagi (especially with riveted
> elements)?  Wouldn't a problem with the 15m driver also throw off the 20m
> SWR?
>
> To test DC continuity, I'll have to drop the antenna (15m driver isn't
> reachable from the tower).  Of course, once on the ground, RF performance
> can't easily be checked, so if things check out at DC I'll still be lost.
>
> Any other ideas/thoughts before I suck it up and put it on the ground to
> test?
>
> --Bill  N7VM
>
>
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