[TowerTalk] from towers to shack

[Roger (K8RI) on TT]

On 12/9/2013 8:58 AM, GARY HUBER wrote:
> Any of the direct burial co-axial cables and direct burial control 
> (cables) should survive underground in plastic or PVC pipe as long as 
> it is drained. The primary difference of direct burial cable coatings 
> is they are less attractive to rodents and other animals or bugs which 
> will chew/eat the plastic.
>

You don't need direct burial cable for conduit, water or not.  All, 
quality coax is water proof. It does get rained on after all. Direct 
burial cables generally have the space with the shield filled with gel. 
This is to prevent water migration if the cable is punctured by a stone 
which is not a concern in conduit.  Connectors are the weak spot. If 
properly waterproofed they should be fine. Having found that the Ultra 
Flex versions of the LMR cables do not stand up well to UV, or weather 
AND having a bunch of the stuff, I now have the LMR-600UF in the conduit.

73

Roger (K8RI)


> 73 ES DX,
> Gary -- AB9M
>
> -----Original Message----- From: Jorge Diez - CX6VM
> Sent: Monday, December 09, 2013 7:29 AM
> To: towertalk at contesting.com
> Subject: Re: [TowerTalk] from towers to shack
>
> Thanks to all for the answers, interesting feedback!, thanks!
>
> Seems I will do it as actually, underground.
>
> Cables will not be direct buried, will go through a plastic pipe, so I 
> don´t
> think that would have considerably more capacitance to ground.
>
> Actually I´m afraid I will find some water or humidity inside the pipe 
> and
> along the cables. Will need to improve that, with a deeper channel, 
> drainage
> and a gentle slope to allow water does not stay inside the pipe.
>
> Lighting is something to improve. A project for next year, very expensive
> since I have more than 18 cables (coaxial and control lines) going to the
> shack. It´s obvious that will need a Polyphaser sponsorship at CW5W :-)
>
> Thanks!
>
> Jorge
> CX6VM/CW5W
>
> -----Mensaje original-----
> De: TowerTalk [mailto:towertalk-bounces at contesting.com] En nombre de 
> David
> Robbins
> Enviado el: lunes, 09 de diciembre de 2013 10:58 a.m.
> Para: towertalk at contesting.com
> Asunto: Re: [TowerTalk] from towers to shack
>
>
>>> Consider a direct strike to the tower? The cables being above or
>>> below ground don't materially change the voltage waveform, at least
>>> as selection of the suppression devices are concerned: it's kilovolts
>>> you need to deal with.
>
>> Cables "tapped" to the tower are coming off a voltage gradient from
>> several
> hundred KV at the top of the tower
>> to zero at ground (if the tower is properly grounded).  At 10 feet on a
>> 100
> foot tower, one had several 10s of KV ..
>> not easily dealt with using simple devices.
>
> But of course ground is not 'zero' once the current traveling down the 
> tower
> gets to it, the ground potential rises also.  What you need to protect
> against are the signal/power carrying conductors having a different
> potential than the shields of the coax or ground where the equipment is.
>
>>> Conventional transient suppression techniques work for phone and
>>> power lines, which run above ground for miles.
>
>> Phone and power lines are not connected to lightning rods several times
>> the
> height of the lines.
>
> Most distribution lines are at the TOP of the poles and get hit directly,
> phone lines are usually 3/4's of the way or more up the poles... and even
> more important they are not coaxial lines so the power carrying 
> conductor is
> hit which takes it directly into transformers, switches, and other
> equipment.
> Important Note, it is not the voltage handling capability of arresters 
> that
> matter, when the arrester turns on from a stroke it limits the voltage
> across itself, that is what its purpose is!  It is the current or 
> integrated
> energy handling capability of the arresting device that is important.  
> How
> you can help it is by keeping all the grounds bonded together, this keeps
> the potential difference between the protected cable and the local ground
> smaller which reduces the amount of current that the arrester must 
> pass to
> equalize the potential between the signal/power lead and ground.
>
> David Robbins K1TTT
> e-mail: mailto:k1ttt at arrl.net
> web: http://wiki.k1ttt.net
> AR-Cluster node: 145.69MHz or telnet://k1ttt.net
>
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