[TowerTalk] grounding

[Gary Schafer]

Rob,

Each installation has different circumstances that can be solved in 
different ways. One of the biggest obstacles I see with a great number 
of hams is they do not really understand what single point grounding 
means. If you put some time into really understanding what is going on 
with that concept you are way ahead of the game no matter what the 
budget is. Just the way things are plugged in at the shack can make a 
big difference.

For example, it is not necessary to have the mains power coming in the 
same place as the coax lines. Just run a power line from a convenient 
place over the where you have your antenna entrance panel. Put your 
power line protectors there. Now run ALL your shack equipment from that 
one power point.

The protectors for the power can be as little as some large mov's that 
will give some protection. Add some gas tubes of the appropriate type. 
If you want to go a little farther add some series inductors in the 
power line ahead of the mov's and gas tubes.

Look at what is in some of these protection devices. It isn't magic it 
is just proper selection of components.

As far as Polyphaser protection devices go, you really don't need them 
if you disconnect the lines from the equipment and ground the shield and 
center conductor of the coax when not in use.

A polyphaser device is a convenient way to ground the shield of the coax 
line at your entrance point. You can do the same thing with a clamp 
around the cable or connector, or plugging the connector into a mating 
connector that is fastened to your ground.
The only other thing that the protection device does for you is shunt 
any lightning energy on the center conductor of the coax to ground when 
you don't have it removed from the rig and connected to ground.

It is more important to connect grounds in the right place than it is to 
have elaborate ground systems.

73
Gary  K4FMX


Rob Atkinson, K5UJ wrote:
> this whole topic/conversation shows a pretty good reason to have 
> professionals install subpanels.
> 
> All the advice, recommendations involving SPG and so on sound great and i 
> won't argue with them as they are correct, but whenever professionals start 
> advising hams on grounding, protection, and so on, they often overlook one 
> major thing--hams usually have stations in homes.   Homes are almost never 
> constructed to be telecommunications sites.    So all the wonderful advice 
> the professional is giving, where in his mind, he is picturing cable trays,  
> backhoes and ditch witches digging trenches everywhere, with gravel all over 
> the ground and the power company coming in with a bucket and three hard hats 
> to put the 3-phase line just where you want it--and when he's done talking 
> the ham says thanks and goes home and unplugs everything and that's the end 
> of that.  I mean, i'd like a little more realistic advice for some guy in a 
> house  who can't move the service drop around back where the tower is, and 
> can't dig a 4' deep trench all the way around the house and cadweld 
> everything to a 4" strap.
> 
> costs:  i once added up the cost of all the polyphasor stuff to do the job 
> right and came up with around $2K.   This is nothing for a guy with $20K in 
> this hobby, but some guy with 2 grand in it will probably balk at that.   
> why do hams not spend  the money on gas discharge devices and all the other 
> gear?   there's a cost/fun price point somewhere in there where a lot of us 
> make spending decisions that aren't always logical or rational--we'd rather 
> blow our money on the fun stuff and take our chances, because that's what a 
> hobby is about, having fun.  I'm not saying that's always okay; i'm just 
> saying that's how it is.
> 
> one final comment:  an all out professional protection job doesn't guarantee 
> you will always be protected--if you don't believe me ask a broadcast 
> station CE.   i know of one A1 station near me that took a direct hit on 
> their 190 degree tower (probably a positive strike) and lost their nice, 
> fairly new s.s. tx--had to get a new one.
> 
> rob/k5uj
> 
> <<<Can you really HAVE a single point ground?  Even if the RF and power 
> service
> entrances were immediately adjacent, and tied together with 3" strap...the
> drop circuits from each will follow different paths, and may have induced
> current on them from the primary strike...with different potentials due to
> their geometries.  I still disconnect everything in the main shack.
> 
> In a 24/7 broadcast installation, or amateur repeater, you clearly can't do
> that.  You take reasonable precautions, and hope for the best.>>>
> 
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