[TowerTalk] Ground system design, RF vs AC

[Gary Schafer]

The whole idea behind the SPG is to have only one ground that the radio 
equipment sees. It has nothing to do with how other grounds are or are 
not tied together.
However it is always a good idea to tie all grounds together. The 
National Electric Code thinks so.

73
Gary  K4FMX


ve4xt at mb.sympatico.ca wrote:
> I'm a little confused by Martin's question.
> 
> I thought the whole idea behind an SPG was to not only 
> MAKE SURE the two grounds were connected, but to 
> eliminate the distinction.
> 
> Have I missed something?
> 
> 73, kelly
> ve4xt
>  
> 
>>From: "Keith Dutson" <kjdutson at earthlink.net>
>>Date: 2005/02/25 Fri PM 03:39:09 CST
>>To: <towertalk at contesting.com>
>>Subject: Re: [TowerTalk] Ground system design, RF 
> 
> vs AC
> 
>>>If you cross-connect your ham & AC power grounds, 
>>
> any such fault currents
> 
>>will flow in your ground system too, for better or 
> 
> worse.
> 
>>AFAIK, every piece of ham gear that uses a three 
> 
> prong AC cord has the
> 
>>safety (green) wire securely attached to the chassis.  
> 
> If you attach a
> 
>>ground strip from the chassis to the ham system 
> 
> ground, does this meet your
> 
>>definition of "cross connect"?
>>
>>Keith NM5G
>>
>>-----Original Message-----
>>From: towertalk-bounces at contesting.com
>>[mailto:towertalk-bounces at contesting.com] On 
> 
> Behalf Of Martin AA6E
> 
>>Sent: Friday, February 25, 2005 3:11 PM
>>To: keith at dutson.net; towertalk at contesting.com
>>Subject: Re: [TowerTalk] Ground system design, RF 
> 
> vs AC
> 
>>Keith,
>>
>>I believe "fault" is the general electrical term for power 
> 
> going where it
> 
>>shouldn't.  That's why we have protective system 
> 
> grounds in AC systems.  If
> 
>>there is a short circuit in an appliance connecting the 
> 
> hot side to the
> 
>>chassis, a fault current flows in the ground lead and 
> 
> the user is protected.
> 
>>A GFCI detects even tiny fault currents and shuts off 
> 
> the circuit asap.
> 
>>(It detects a difference between hot & neutral current, 
> 
> as you
> 
>>suggest.)  That's a good thing, but old-fashioned fault 
> 
> protection involves
> 
>>blowing the upstream fuse or breaker with an 
> 
> overload current.
> 
>> That's one reason why your branch circuit wiring has 
> 
> to be matched to your
> 
>>breaker - to be sure it will trip quickly if there is a 
> 
> short.
> 
>>If you cross-connect your ham & AC power grounds, 
> 
> any such fault currents
> 
>>will flow in your ground system too, for better or 
> 
> worse.
> 
>>-Martin (who is not an electrician)
>>
>>--- Keith Dutson <kjdutson at earthlink.net> wrote:
>>
>>
>>>You wrote:
>>>
>>>>The problem with connecting the AC green wire to 
>>>
> the radio room
> 
>>>ground and
>>>then connecting my bulkhead "SPG" to a new 
>>
> ground rod or even a 
> 
>>>perimeter ground connection is that my radio 
>>
> installation becomes part 
> 
>>>of the AC protective ground system for the house.  
>>
> That is, any house 
> 
>>>fault or other current will partly be routed through my 
>>
> radio ground 
> 
>>>system. Is that what we want?
>>>
>>>When you say "house fault" I assume you are 
>>
> referencing a ground  
> 
>>>fault  circuit interrupter (GFCI) system.  Such a 
>>
> system interacts with 
> 
>>>the  white  neutral ground, not the green safety 
>>
> ground.  So the answer 
> 
>>>is yes,  we do  want the safety ground connected.
>>>...
>>
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> 
> Supporting Towers", "Wireless Weather Stations", and 
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