Esteemed TowerTalkians,
I have a 250' long RG8X cable that was used to return the "dumped" power
from my 80M 4sq to a power meter and dummy load at the operating position.
Somehow it got cut in two places and had a chance to absorb a lot of
weather before I discovered it in a walkthrough (hadn't been using the 4sq
while I was making some changes over the summer).
I use my Autek RF-1 to test coax (among other things) so I trimmed the coax
back a bit, hoping to get past the deteriorated area without having to
discard the whole cable, and tested the SWR on the unterminated line.
Ouch! It was only around 4.2 to one at 35 MHz (14+ but not "H" on the
Autek even at 2 MHz). I am used to seeing "H" or close to it through most
of the HF spectrum when I test coax this way. I started chopping off a
couple of feet at a time, expecting the results to improve gradually. I
was thrilled to see a steady improvement to 10-to-one with the first few
chops, but just as I was congratulating myself it started to drop. After
maybe 20' it had dropped to 2.6 to one, then started to rise as I cut
further. It looks like the same cycle is being repeated at some wavelength
related to 35 MHz.
I guess the cable is a goner, but I am interested: what is happening here?
Please reply directly and I will summarize to the reflector if the
learnings appear of general interest.
73,
Jim, VE1JF
email to 74273.2073@compuserve.com
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