Gary,
I went through this exercise this past summer.
I finally decided to just bury the stuff. I went ahead and put in a
couple extra runs of LMR-600 and control lines for future growth or
repairs.
I had a couple direction changes on my path from the tower to the shack
and decided it would be a pain to pull the cables over 300' anyways.
The idea of avoiding water and critter issues was checked off on the pro
side of direct burial.
Rich - N5ZC
On 1/28/2016 7:22 AM, StellarCAT wrote:
My ongoing tower/antenna projects... hopefully I’m not boring others out
there...
I had planned on burying all lines to the towers (2, one at 150’ out and one at 300’ out) ... at first I
thought in solid joined (sealed) PVC which I can get for $9/10’ ... and I’ve also thought about direct
burial which for the coax and control cables has the added benefit of increased capacitance to ground and thus a
reduction of energy (lightening event) that reaches the shack... but control cables aren’t normally rated for
direct burial... or at least I don’t think so (researching that now)...
Then this latest QST article on coax says DON’T bury in any type of conduit be
it plastic or otherwise. It says condensation WILL get inside and ruin (flood) the
cables.
So .... if the cables are underground – below the frost line – say minimum 1’ down (upstate SC) ... how will condensation develop? Or
will it? I’m an engineer (HW/SW development) and reasonably intelligent but find it difficult to wrap my head around this issue... will it or
won’t it – flood that is? if it were always under ground – including both ends then I’d think not.... but it isn’t always
under as the ends come up to and above the surface... does that introduce a temperature variant enough to induce condensation? And I don’t like the
idea of holes in the plastic – that just means mud will indeed eventually work its way inside.
Maybe use corrugated tubing (again – no cuts or openings) ... this would allow
whatever moisture there might be, and I can’t imagine its going to be a great deal, to
settle in the lower points of the corrugation.
Comments from others that have been through this - in the south with similar
conditions would be appreciated.
Alternatively I could use a leader line and go from say 15’ on the first tower to the second tower and then that
same level to the shack with supporting 4x4 poles along the way... but this seems iffy as well as first the cables are
‘leaving’ the tower above ground potential so that might mean a higher voltage (common mode –
probably?) on the lines (again: lightening type event)... and the first tower is a rotating tower ... although thinking
about it that might work quite well to go from the tower with a ‘swing-arm’ of hanging coax/cables to allow
rotation.
thoughts?
Gary
K9RX
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