I use "UF" Romex for all control/rotor lines and hardline. I direct buried
it and it has been fine for almost 20 years. Two feet deep might be deep
enough to be trenched over safely to add something later. The Romex keeps
voltage drop to a minimum. I go up the towers with the regular rotor cable
etc.
Chuck W5PR
On Thu, Jan 28, 2016 at 7:22 AM, StellarCAT <rxdesign@ssvecnet.com> 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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