Hi Doug,
We had a similar issue with an LDF5-50 feeder at K6IDX, except that the line
had been in place for more than 15 years IIRC. The connectors had been
installed by a celltower professional, with a very thorough multilayer taping
regime. So moisture had been kept out for a long time, or so we thought.
We started to notice we didn't 'feel' as loud as we used to using the antennas
on that tower. Our initial response was 'can't be the feeder, let's look
elsewhere'. Having tried many possibilities up the tower and on the antennas,
we finally decided to break the (ground-level) connection and cut back the
cable. Don't want to alarm you, but we had green copper salts discoloring the
foam dielectric quite a ways along. We decided to keep cutting back, one foot
at a time, until we got to new-looking cable. Memory says it was about 10 feet
or so...
I still have a one foot length we removed, hanging on the workshop wall. It's
there as a reminder that even professionally and correctly installed outside
devices can be the source of trouble over time - and to follow a logical
troubleshooting path at all times. I'm sure a TDR would have got us there
faster...
73, David G3WGN M6O WJ6O
Hired gun at K6IDX 2002-2009
-----Original Message-----
From: kr2q@optimum.net [mailto:kr2q@optimum.net]
Sent: 16 October 2017 00:00
To: kr2q@optimum.net
Cc: towertalk@contesting.com
Subject: [TowerTalk] More information about my problem; . Re: Heliax acting
strangely: Help?
I was wondering why I did not get any follow up emails to my original. I had
made an additional post, but in error, I only hit reply and it never went back
to the group. So trying again.
As a reminder, I have 160' run of 7 eights Heliax what worked fine all last
summer, fall, and winter. Last time it saw power was at the end of January.
About 6 weeks ago, I turned on radio and shot out 100 watts and found an SWR of
3:1. I did all the normal checks and the problem is actually the coax.
Putting a dummy load at the far end still showed 3:1 and when I put the dummy
at the jumper feeding the near end (in other words, bypassing the coax), the
SWR was 1:1. I opened up both ends and found no water and no moisture. Sorta
like the X-files. It's not the antenna, so you don't need to know what it is.
Here is my additional post from a month ago.
de Doug KR2Q
I have multiple responses already. Here is some more information.
I do not have real connectors for 7/8 Heliax. I took a chassis mount SO239 and
soldered it to the cut end (each end) of the heliax. I used copper wire to
make the connections.
Therefore, there is no water in the connector because there isn't a
"connector." I did have them taped up with Scotch 88.
When I opened them up, there was no moisture inside and certainly no liquid
water.
Both ends were, and are, well above ground (measured in feet), so no, they were
never sitting in water.
Each end has a "loop" of RG8 connected to it, so there even if rain were to
"run down the coax," it would or should just drip off the bottom of the RG8
loop...no way to travel up hill back to the "connector" with the Heliax.
The connections (wire soldered to the outer conductor and to the center
conductor) are no longer "shiny" but are electrically sound (DC).
As I said, this has been in use since last Summer, through the fall and winter
(through Jan 21, 2017) without issue.
As for water ingress, where would that occur? Would the dielectric "suck up
water?"
I really can't see where the water would come from and if any, "not enough" to
make that much of a difference in the course of ~6 months?
I don't have a TDR and locals who have responded have various MFJ analyzers,
but not one that has TDR capability. But seems that is a good route to
follow. Would be great to identify an impedance bump somewhere.
Yes, at some point, I can cut off the ends and see what happens, but how much
should I hack off?
Any other thoughts?
Thanks
de Doug KR2Q
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