[TowerTalk] Cautionary tale about cable waterproofing

[kq2m at kq2m.com]

Pete,

Water inside of any cable is an issue - at a minimum it means that the 
there exists the possibility of a hole or holes in the outer jacket of 
the cable.  Has your tower been hit by lightning?  A lightning strike 
can easily cause heating of the cable which can cause the cable itself 
to swell or burst the insulation on the individual wires within the 
cable opening it up to shorts, especially as water gets in.

I've had lightning hits here in CT that have caused this problem, with 
the rotator control box indicator acting "flakier" and more erratic with 
time until it stopped indicating.  I eventually replaced the rotator 
cable, pulled the old cable off the tower, did a necropysy on it and 
found areas of almost microscopic holes in the outside jacket of the 
cable leading to water ingress which then allowed water to get into the 
strands of the conductors as there were tiny but visible bulges in the 
white insulation around the wires where there were barely visible holes. 
  All of this no doubt from the multiple lightning strikes.

The rotator still worked for months afterwards until the problem grew so 
vexing that I swapped out my rotator and took the rotator cable down and 
ran a new one.  End of problem.

I would be more concerned with any water inside the cable when it gets 
cold enough to freeze, because water freezing expands in size as it 
becomes ice - so the expansion in volume of the ice will most likely 
enlarge any holes/breaks in the cable that you might have.  It might 
also break individual strands within the wires.  Not a situation you 
want.

The problem with lightning strikes is that often you can't see where the 
holes/breaks might be on the outside of the cable.  And then you can't 
see any holes/breaks on the inside of the cable because of the outer 
jacket.  So you may or many not have a problem.  But if you do see 
bulges or holes/breaks in the cable, then you should replace it.  
Otherwise you just postpone the inevitable as the cable will eventually 
fail.

73 and GL!

Bob, KQ2M


On 2024-07-18 08:56, Pete Smith N4ZR wrote:
> It's hard to say whether the water has anything to do with my rotator's 
> current failure to turn.  Internal insulation looked fine, but  I 
> measured 60 ohms between the two motor leads at the bottom of the tower 
> - if the rotator is up against the limit stop (as I think it is), then 
> the limit switch should have opened and there should be no connection 
> at all.  From memory, I think the motor winding should have been around 
> 8 ohms.  Looks like the antenna needs to come down to determine where 
> the problem is...
> 
> 73, Pete N4ZR
> 
> On 7/17/2024 10:23 PM, john at kk9a.com wrote:
>> I use THHN for the motor wires and a multi-conductor for the sensor.  
>> I try
>> to seal the cable ends but I do not make a big effort to seal them.  I 
>> have
>> never noticed water in any of my control cables but even if there was, 
>> I
>> don't see how water inside the PVC cable jacket would effect it since 
>> the
>> conductors are insulated.  If water got inside the connector at the 
>> rotator
>> it would likely have an effect, this is common with Yaesu rotators, 
>> their
>> boot does not make it water tight.  I have had very few actual rotator
>> problems but I have had several issues in the last few years with 
>> failed
>> lightning protectors.  Pulse type seem especially sensitive to 
>> leakage.
>> 
>> GL
>> John KK9A
>> 
>> 
>> Pete Smith N4ZR wrote:
>> I've been having problems with my rotator, currently stuck due west.
>> Today, in order to verify connection from the controller in the shack, 
>> I
>> cut open the jacket of the good quality 6 x #18 cable at the tower 
>> base
>> - imagine my surprise when water flowed out of the cut, even though 
>> all
>> the cable above that point is vertical.
>> 
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