[TowerTalk] It's Always Something

["K8RI" <K8RI-on-TowerTalk@tm.net>]

Couple weeks back I was taking a late night break from DXing on 40 for a 
good old fashioned RagChew.
After about a half an hour I notieced the SWR was bouncing a bit and it's 
normally rock solid.  My first thought was the roller inductor in the tuner, 
but no mater what I did it still was going from nothing to over 100 watts 
reflected.  The SWR was too high to run full power without the tuner, but by 
moving down near the bottom of the band I was able to get over 800 out and 
the reflected power was bouncing again.

Going back to 7.155 with near a perfect 1:1 showing no reflected power at 
100 watts I kicked in the amp (Tokyo Hy-Power HL-1.5Kfx) as slowly brought 
the drive up.  The Reflected power stayed zip until between 400 and 500 
watts out and then it began to jump around.

The antenna is a plain old center fed, half wave dipole with the high end at 
roughly 90 - 95 feet and hanging at an angle of about 60 degrees. It has a 
W2AU balun in the center with about 80 feet of the old 9913 coupled to about 
60 feet of LMR-400 in 2" conduit.

I wanted to check it out piece-by-piece, but unfortunately the splice (2 
PL-259s and a F to F UHF connector) were about 1' into the end of the 
conduit which meant a bit of climbing, removieng two 10 X 10" terminal box 
covers and pulling the first 6' fromt he rig back into the contuit. So it 
took me a while go get up the ambitiion to start.  Having a history with 
9913 I expected water in the cox, but that would have to mean either the 
balun was physically broken or the water proofing had failed. Thing is, I'd 
had the antenna down the week before and it looked good.  This was before 
the week of 20 degree above normal weather followed by a week of 20 below 
nornal and two bad storms.
Now I was beginning to worry about that solid state amp.

When I was able to pull the coax back far enough to get at the splice, I 
found water running out before I finished taking the tape off.  That still 
left the problem of how it got in.Dropping the antenna and cutting the 
flooded heat shrink off did not find water inside and the connector was 
flooded with DC-5 compound.  I took the coax inside the shop where it could 
dry off and I could get a better lookat it.

About 10 feet from the balun I found one abraded spot on the jacket, but it 
was still intact.  However about a  foot farther down I found nearly half an 
inch of exposed braid.  I did not find any other discontinuities in the 
jacket.  It's about a 50' drop from the abraded spot to where the coax 
enters the building through the conduit.with the other end of the coax being 
only a couple feet farther.

There is absolutely NOTHING within 20 feet to either sied of the coax at the 
abraded spot.  The only thing I can figure is the spot was already there 
when I put the caox up and I missed it when inspecting the cable, but that 
gets done every time the antenna comes down and it's been down at least 5 
times since it was installed. It is after all on a rope through a pulley at 
the top of the tower. Raising and lowering takes all of a minute or two.

But to give 9913 its due, it was not the fault of the 9913 or of the water 
proofing at the connectos.  It was *aparently* an abraded jacket which most 
any coax could suffer, but it does say a lot for those using the tougher PE 
jackets. I just can't figure out how, or when it was abraded. it apparently 
took that last 5 months for the water to work its way in and down to where 
it became a noticeable problem  BTW, the braid is still nice and clean even 
where exposed.

Ah, well...this gives me a chance to try out the CNT-240 on one of the 
antennas.
I think I'll take the opportunity to install the 6-pack and remote antenna 
awitches for 75 and 40 as well.  That'll save some coax and quite a few 
connectors.  Working this way the CNT-240 drops from the antenna with only a 
slight catenary to about the 10' level on the tower and then down to the 
grounding plate. That should be a run of about 70 to 80 feet.   From there 
it's LMR-400 to the remote switches and 6-pack.  From the house/den/shack to 
the 6-pack and from the shop to the 6-pack with LMR-600.  Runs to 6-meters, 
144 and 440 are (or will be) LMR-600 all the way.


I've noticed with all this work I'm getting to the age where I have to work 
out a lot more to stay in shape to climb and work on the tower.

73

Roger (K8I) 

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