> -----Original Message-----
> From: towertalk-bounces@contesting.com [mailto:towertalk-
> bounces@contesting.com] On Behalf Of Roger (K8RI)
> Sent: Thursday, September 13, 2007 3:48 PM
> To: towertalk@contesting.com
> Subject: Re: [TowerTalk] SPG & Service Entrance Grounds.
>
> I know we are beating this to death, but it is a topic that I think
> deserves
> the attention.
>
> No matter which way we go with alternatives we run into conflicts or the
> actual term Single Point Ground ( SPG) which requires a definition.
>
> >>
> >>Sometimes these alternatives are all that can be done at a particular
> site
> >>but they are not "single point ground systems" and should not be called
> >>such.
>
> Agreed.
>
> >
> > ------------ REPLY FOLLOWS ------------
> >
> > My point exactly. In English, the word "single" has a specific
> > meaning. If you have more than one ground point but you use the word
>
> Here we have to be careful and remember the ground point is where the
> equipment ties into the ground system.
>
> > "single", you are confusing the issue. There is nothing wrong with
> > saying "Double Point Ground" or "Multiple Point Ground" or "Multiple
> > Ground Points".
>
> Except they do not convey the concept of a single point ground If that is
> the goal.
> First we need to think of "ground" as a "system" of wire and ground rods.
> Unless it's the only ground rod, each ground rod doens't represent a
> "ground
> point" as it is no more than an *extension* of a grounding network or
> system. By themselves, the service entrance, phone line(s), antennas, and
> cable each represent a ground point where they enter the home which in
> this
> case would be 4 ground points. If allowed to remain seperate the
> equipment
> tied to them can rise to different potentials (sometimes drastically
> different) from a nearby or direct lightning strike. Generally, codes
> require all of these be tied together to form one single system. Even
> metal
> water and gas lines are required to be tied into this system.
>
> My satellite receivers have a ground to the AC mains, but they also have a
> telephone line, antenna(2), and cable connection. This is not a good
> thing
> as it is one of the reasons for damage caused by nearby lightning strikes.
> In those satellite receivers I'd have 4 systems coming in that are
> seperated
> by a lot of fragile and expensive components. From an engineering
> approach
> one point on this system needs to be selected to which all equipment
> grounds
> are tied. This single point then becomes the "Single Grounding Point" for
> all of the electrical equipment. Hence the term, Single Point Ground. The
> problem with this term has been well covered, but any of the proposed
> alternatives mean something else. OTOH if a station, or home doesn't have
> a
> SPG then call it what it is.
>
> A home, or shop my have multiple grounds such as the electrical, phone,
> antennas, and cable. These grounds all need to be tied together to create
> "one ground system". If they all tie together at one point such as the
> bulkhead and all equipment is grounded to that point then each, or rather
> all the equipment sees the entire ground system as one single point.
> Refering to more than one ground point could be interpeted as each piece
> of
> equipment such as the electrical mains, telephone, antennas, and radio as
> having their own indivicual grounds and that is we are tying to avoid.
> "Common point ground" also has a problem as there is a point where an
> electrical system "common" is grounded.
>
> >
> > Please call it what it is.
>
> That's the problem. Finding a term that really means the grounds for
> everything are tied to one single point which is the goal.
>
>
> 73
>
> Roger (K8RI)
>
> >
> > Bill W6WRT
Roger,
What you describe "tying all the grounds together to form one ground system"
makes for a common ground system but it does not make a single point ground
system. You only have a single point ground system when all cables and the
ground going to a piece of equipment share a common physical place.
No ground leads connecting together the cable grounds to the electrical
ground etc. If there is a wire or strap between the electrical ground
system and the coax ground plate you do not have a single point ground
system.
73
Gary K4FMX
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