How about a "local area single point ground"?
[mailto:firstname.lastname@example.org] On Behalf Of Roger (K8RI)
Sent: Thursday, September 13, 2007 4:48 PM
Subject: Re: [TowerTalk] SPG & Service Entrance Grounds.
I know we are beating this to death, but it is a topic that I think
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
>>but they are not "single point ground systems" and should not be
> ------------ 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
First we need to think of "ground" as a "system" of wire and ground
Unless it's the only ground rod, each ground rod doens't represent a
point" as it is no more than an *extension* of a grounding network or
system. By themselves, the service entrance, phone line(s), antennas,
cable each represent a ground point where they enter the home which in
case would be 4 ground points. If allowed to remain seperate the
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
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
telephone line, antenna(2), and cable connection. This is not a good
as it is one of the reasons for damage caused by nearby lightning
In those satellite receivers I'd have 4 systems coming in that are
by a lot of fragile and expensive components. From an engineering
one point on this system needs to be selected to which all equipment
are tied. This single point then becomes the "Single Grounding Point"
all of the electrical equipment. Hence the term, Single Point Ground.
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
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
"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
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
equipment such as the electrical mains, telephone, antennas, and radio
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.
> Bill W6WRT
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