Re: [TowerTalk] grounding questions

[Phil - KB9CRY <kb9cry@comcast.net>]

I'll take a stab at your questions.  First I'm no expert but these guys 
are; read thoroughly through their technical articles on Ham Station 
grounding.  http://www.polyphaser.com         
http://www.arraysolutions.com/Products/ice/index.html
Personally I use all ICE devices but both are the same.


> I have the ground rods in at the tower running from each tower leg ( 
> tower is Rohn 25), 1 st rod is 8' out and the other 2 are 16' apart 
> altogether 40' from the tower to the last ground rod in each 
> direction. On the ground rods running toward the shack I have the 
> ground wire running toward the trench for the coax run and then ground 
> rods every 16' to the box outside the shack. 

Polyphaser suggests each tower leg ground radial be at least 75 ft long 
with ground rods spaced along that length as appropriate.

> I have a metal box at the bottom of the tower and one outside the 
> window of the shack ( I know I probably only need the one at the 
> bottom of the tower but I want to be a safe as I can be as far as 
> lightning). 

No, the one just outside the shack is numero uno.  You need to ground 
the coax shields at the tower but can do the rotator cables at the SPG 
(see below for SPG).  Also, attach a wire from the mast to the tower, 
allow enough loop for rotator, just above the rotator to shunt any 
strike energy from the mast to the tower so it doesn't go through the 
rotator.  I use a short piece of welding cable for this.

> In each box are lightning arrestors( ICE units) for the coax runs and 
> the control lines. 

Overkill really.  Call Mike at ICE and ask him if you'll be receiving 
the same coax shield protection by using a ICE device at the base of the 
tower rather than their coax shield grounding buss and adapter.

> On each unit is a ground lug. Do I need to run wires from each of 
> these lugs and then attach them to the lightning ground or are the 
> units grounded though the metal boxes? 

IF the units are bolted to the metal boxes then you don't need to mess 
with the lugs.

> If the units are grounded thought the metal boxes  then can I tie all 
> the grounds on the control lines to these lugs and free up and extra 
> terminal on the arrestors to use for the other control line coming in? 

What do you mean by these this statement?  I'm not following the process 
here.

> These lugs don't look  big enough to use the #6 wire I using on the 
> rest on the lightning ground. What size wire is recommended? 

Whenever I use these lugs I use #12 solid.  #6 is a little small for the 
main grounding wire size.  I use #4 bare solid (don't use stranded) for 
my main outdoor grounding wire.  What size is being used to connect to 
each ground rod?  Tie the tower grounding wire to the a lug on the metal 
box; that's how I tie mine together.

> In the shack I have one #6 wire coming in that is grounded to a single 
> separate ground rod out side. This is for the equipment grounds in the 
> shack, again the ground terminals on all the equipment in the shack 
> look to small to use this big wire. I was thinking would use a split 
> copper bolt to attach smaller copper wires to this bigger wire is this 
> the correct way? 

If the shack grounding main wire is more than about four feet long, then 
you'll want to use a very low impedance wire.  Some guys use 1-1/2 braid 
and some use large welding cable (made of hundreds of very small 
wires).  Both of these types have far more wire surface area then #6 
wire (energy flows on the outside of the wire and therefore you want to 
max out wire surface area).  Personally I have both types for a shack 
ground, a braid and welding cable. 

> One more dumb question when running the wires from the equipment 
> grounds to the ground wire coming into the the shack do I run 1 wire 
> from each piece to the main wire or connect them from 1 piece of 
> equipment to another then from the last piece of equipment to the main 
> wire?
> I think the right way is each piece of equipment to the main wire. 

Use smaller wires from each piece of equipment (#14 or #12) and attach 
them to these wires.

> I figure that since the ground wire coming from the tower to the shack 
> is only a few feet from the single ground wire coming into the shack 
> that I don't need to tie these together and I wrong here. 

Yes, wrong.  The tower grounding system, the metal boxes, the shack 
ground, and the electrical service grounds are all tied together at your 
SPG, single point ground, which should be another ground rod pounded in 
right outside the shack.  The electrical service ground should be routed 
outside the house and should be large, I use #4 bare solid again.
Finally how do you attach your wire to the ground rods?  If you use 
clamps, then you'll have to religiously go out and retighted them at 
least four times or more per year; believe me, they will loosen up with 
every thermal cycling of the weather.  The best is to CadWeld.  Go to   
www.erico.com   or to  http://www.harger.com/  and check out the 
OneShots or UniShots.  These exothermic welds result in a weatherproof, 
maintenance free connection that you can bury with the ground rod.
Gd luck, sounds like you're on the right path.  I never disconnect and 
never have had a problem.  73  Phil  KB9CRY

> And before anyone brings it up yes the ground wire is going to 
> continue to the same point that the ac and telco lines are grounded to
> Thanks and 73
> Rick
> KC5AJX
>
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See: http://www.mscomputer.com  for "Self Supporting Towers", "Wireless Weather Stations", and lot's more.  Call Toll Free, 1-800-333-9041 with any questions and ask for Sherman, W2FLA.

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