[TowerTalk] Replacing station ground

Wed May 30 18:52:40 EDT 2018

Agreed!

There is a new version of the Motorola R56 manual. Make sure you find it.

The older version (early 2000s) is good too. The new one is twice the size.

Thanks
73
Jim W7RY (Motorola Solutions)

-----Original Message----- 
From: Bob Matthews
Sent: Wednesday, May 30, 2018 2:38 PM
To: Fred Keen
Cc: towertalk at contesting.com ; Bob Shohet, KQ2M
Subject: Re: [TowerTalk] Replacing station ground

Hi Bob

You may want to download the Motorola R56  pdf file online. Also QRZ dot com 
has a 3 part forum on station grounding hosted by a PE who installs and 
inspects cell tower sites. Both are a very interesting and informative read.

Whenever I pass coax or hardline through box enclosures or panels, I find 
1/2” - 1” J-cord connectors work great in keeping out the insects and 
moisture. Just pick the size that suits your feedline diameter. They are 
available in standard and Liqui-tite. Home Depot and any electrical supply 
house usually stock them.

Usually #4 solid copper wire is adequate for grounding.

Hope this helps you out some.

Bob Matthews  KT3RR
Sent from my iPhone

> On May 30, 2018, at 15:07, Fred Keen via TowerTalk 
> <towertalk at contesting.com> wrote:
>
>
> Hi Bob,
> I like the MFJ 4603 thru window approach. If your window is not wide or 
> tall enough to get all the connections with it, you might consider making 
> one with plexiglass,
> see one here: Building the shack - window feed thru panel done!
>
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> Building the shack - window feed thru panel done!
>
> Plexiglass window feedthru panel
> |
>
> |
>
> |
>
>
> Be sure to post some pictures of your antenna farm.
> Fred KC5YN
>    On Wednesday, May 30, 2018, 1:04:14 PM CDT, Bob Shohet, KQ2M 
> <kq2m at kq2m.com> wrote:
>
> I am planning to completely revamp my station placement and station ground 
> and have been thinking about and researching different ways of doing this 
> for several years. I have also studied what was done at many stations at 
> which I have operated, but that only confuses the issue more as each house 
> and terrain is different and every station owner has their own way of 
> doing things.  :-)  I have also spend considerable time reading the 
> Polyphaser material and W8JI and K9YC’s websites.  So I have several 
> questions and would appreciate your help.
>
> First, here is what I am planning to do:
>
> Install a metal Hoffman box at each tower and then ground the coaxial 
> cables, rotator cables and control cables at the box (the control cables 
> are already grounded to the tower) with a #2 Copper wire grounded 
> connecting to multiple short ground rods (because of the ledge right 
> underneath) and the tower.
>
> Then I will run all the cables to a larger metal Hoffman box grounded just 
> outside the shack and a few feet from the utility ground, telco and cable 
> grounds.  Then, in a trench ~ 1’ deep around two sides of the house to 
> form a perimeter ground, I plan to connect a series of 8’ copper clad 
> ground rods culminating with a connection to the Hoffman box outside the 
> shack and to the utility, telco and cable grounds, so that I will have a 
> single-point-ground connected to a perimeter ground in the trench.  I will 
> then fill in the trench when done.
>
> Questions:
>
> 1) How far away should the trench be from the house foundation?  6”?  A 
> foot?  more?  I know that there should be some separation but do not know 
> how far is best.  I live in Western CT near the NY border where we get a 
> lot of ice and snow and it has gotten down to –20 F; so frost heaves are 
> always an issue.
>
> 2) I assume that the best and safest way to connect all the grounds would 
> be to use #2 copper wire running between the Hoffman box and the 
> utility/telco and cable grounds.  Since these ground wires are all 
> connected ABOVE ground, is there any risk to removing the wires and 
> replacing them with a single #2 Copper wire below ground?  If there is 
> risk with removing the utility ground temporarily to do this, then should 
> I simply dig down and then connect #2 copper wire to the same utility 
> ground rod  below ground – thus avoiding the need to remove the utility 
> ground above ground to connect all the grounds?  Is there a problem that 
> could be created by having an oxidized copper clad ground rod of the 
> utility ground with connection above ground and then simply sanding a spot 
> lower on the same rod below ground in the trench and then connecting the 
> Hoffman box to that below ground?
>
> 3) I need to get about 6 control cables, 6 rotor cables and 8 coaxial 
> cables into the shack.  How would you suggest that I do so without 
> allowing critters and insects in?
>
> I see two potential options:
>
> A) There is a small window to the shack about 12” high and 24” wide – if I 
> replaced the window with an aluminum plate (which would be grounded to the 
> single point ground), I will use  standoff coaxial connectors to get the 
> coaxes inside, but I don’t  think that I have enough room to mount 
> everything on the plate, so how do I get the control cables and rotator 
> cables inside without making another hole and allowing the critters in?
>
> B) If I don’t replace the window with a panel, then how do I get all the 
> cables inside without allowing critters and insects inside other than 
> making a big hole in the house above the top of foundation and then 
> stuffing it with steel wool and other material?  This would allow cold air 
> and humidity to get into the basement as well and provides a potential way 
> in for all kinds of insects and mice.  Not a desired outcome.
>
> 4) Due to the extremely violent wx that I get at my qth I still like the 
> idea of disconnecting everything when not in use.  With this in mind, does 
> it make sense to have another aluminum panel inside the shack mounted on 
> wooden beams near the window (and grounded to the spg with #2 wire) to 
> which I attach all the coaxial, control and rotator cables inside the 
> shack and then simply disconnect them and move them away when not in use? 
> These outside and inside cables would also be disconnected from all the 
> equipment and outlets and ground inside the shack would be disconnected 
> from the single point ground outside.
>
> I would appreciate any thoughts, suggestions or warnings about what I 
> propose.  Thank you for your help!
>
> 73
>
>
> Bob KQ2M
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