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@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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