Doug,
Heliax uses closed cell foam so the dielectric itself doesn't wick
moisture, but there are voids between the dielectric and shield that can
wick water. You must ensure a seal at the ends of corrugated hardline if
you want a long life feedline.
Did you place the dummy load right at the end of the Heliax, or at the
end of the top jumper?
-Steve K8LX
On 10/15/2017 18:59 PM, kr2q@optimum.net wrote:
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
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|