What is RF ground?
 

"John Smith" wrote in message
...
Wayne wrote:
"John Smith" wrote in message
...
David wrote:
What would you define RF ground as? There seem to be a lot of different
ideas.
David:

Ground can be a relative thing. What I have always found to be good
advice is that EVERY ground, at some point, be allowed to reach a low
ohmic earth ground (best possible if it all occurs at the exact same
earth ground point--or no current flows and there is no voltage
potential between such grounds.) For example, although a dipole needs
no rf ground directly at the point it connects to the feed-line, the rig
hooked to such an antenna and feed-line should be given a good earth
ground.
snip

Regards,
JS

When you refer to hooking the rig/dipole to a good earth ground, are you
still talking about an rf ground, or a safety ground?
I see no requirement to connect a nicely matched dipole to an earth
ground for rf purposes. For example, a battery operated transmitter
feeding a dummy load wouldn't need one either.

Wayne:

Both. Only a dummy would think he needed an rf ground for a watt burner
of proper impedance.

However, there always is that "special case;" if the nitwit was running a
kw off a forklift battery, he just might want that rf ground.

JS

Well, my question is in the context of rf ground being a function of the
antenna subsystem. It wasn't clear why you recommend use of a transmitter
rf ground, if the antenna system doesn't require it. Yes, I would run some
sort of rf ground at the rig if I were using a random wire fed with a tuner
in the shack, because the antenna system requires it.

My own setup is a ground mounted vertical with a modest 10 foot diameter
ground system. The "rf ground" is at the base of the antenna (as is a
separate lightning ground). The shack is on the second floor, and has only
a safety ground at the rig.

What is RF ground?
 

Wayne wrote:
"John Smith" wrote in message
...
Wayne wrote:
"John Smith" wrote in message
JS

Well, my question is in the context of rf ground being a function of the
antenna subsystem. It wasn't clear why you recommend use of a transmitter
rf ground, if the antenna system doesn't require it. Yes, I would run some
sort of rf ground at the rig if I were using a random wire fed with a tuner
in the shack, because the antenna system requires it.

My own setup is a ground mounted vertical with a modest 10 foot diameter
ground system. The "rf ground" is at the base of the antenna (as is a
separate lightning ground). The shack is on the second floor, and has only
a safety ground at the rig.


Wayne:

I see...

An antenna design requiring a system of underground ground radial(s) to
function correctly (or at least as designed), (or, for that matter,
above ground radial(s) running though bushes) would only be a "complete
antenna" if such were taken for granted had already been installed
(meaning the "rf ground-establishing" radials.)

And, if there were any chance at all I would be running a kw, and
touching both the ground radials and the ground at the same time AND
wanted to cover all special case/weird/worst-possible-cases (and I do
propose everyone should plan on this)... I would provide a nice low
ohmic earth ground for such radials (possibly useful for safety only.)
But then I am a sissy and find rf burns painful.

I didn't realize you were asking me, "If the guy has only installed half
of the antenna, should he install the "other half?" The answer to that
is all too obvious.

Yanno, those trick questions always throw me!

Regards,
JS

What is RF ground?
 

David wrote:
What would you define RF ground as? There seem to be a lot of different
ideas

An ideal RF ground is a point or node where RF current can be imposed
and the result is no change in RF potential (voltage). That is to say
the impedance is zero. All real world implimentations of "RF ground"
are less than perfect as measured by their real world impedance.

What is RF ground?
 

ORIGINAL MESSAGE:

On Sun, 12 Nov 2006 15:14:49 -0000, "Dave" wrote:


but rf doesn't flow 'into the earth'

------------ REPLY FOLLOWS ------------

Beware of making broad statements that are supposed to be true in all
cases. The one above is not.

Bill, W6WRT

What is RF ground?
 

In article ,
Bill Turner wrote:

ORIGINAL MESSAGE:

On Sun, 12 Nov 2006 15:14:49 -0000, "Dave" wrote:


but rf doesn't flow 'into the earth'

------------ REPLY FOLLOWS ------------

Beware of making broad statements that are supposed to be true in all
cases. The one above is not.

Bill, W6WRT

One statement that IS True, and has been around "Forever":

Ground is not Ground, the World Around........


Me and RF Ground, is not Ground Ground........

float? What is RF ground?
 

the real fooling part is somthing kinda simple, can be sooo tricky

In article ,
Richard Clark wrote:

Hi Myles,

Let's just cut to the chase with some selective editing:

On Sun, 12 Nov 2006 16:14:21 GMT, ml wrote:

Any violation of this last rule brings grief.
Such violations are legion and few escape.

(presume my electrical gnd is ok on the aka 3prong plug)

B I N G O !

You have won the traditional violation of the rule. This is the
meaning of "legion," there are many, many, many such examples. Those
who violate this rule are often blindsided by other violations along
the way.

What is the third prong of the 3 prong plug for? Most would say
ground (and be blindsided to the complete term being "safety" ground).
The 3rd prong is not designed to be current carrying in the
conventional sense, only in the safety sense when the neutral wire or
hot wire becomes exposed to the device user (basically forcing a short
circuit that then opens through a blown fuse).

So, you have TWO paths to ground:
1. Through neutral;
2. through safety ground.

The question becomes:
"What is the quality of it being RF ground?"
Answer:
"Neither 1 nor 2 above were ever considered
in those terms. Hence the quality of their being
RF ground is unknown and the presumption of being
poor examples is a reasonable expectation."

The next question becomes:
"Why do I need their ground proximity?"
Answer:
"You don't - unless...."

Unless
1. You are powering off the Mains;
2. Powering off battery that is being recharged off the Mains.

Both numbers 1 & 2 are a frequent blindside to those attempting to
isolate ground loops.

73's
Richard Clark, KB7QHC

What is RF ground?
 

Me wrote:
In article ,
Bill Turner wrote:

ORIGINAL MESSAGE:

On Sun, 12 Nov 2006 15:14:49 -0000, "Dave" wrote:


but rf doesn't flow 'into the earth'
------------ REPLY FOLLOWS ------------

Beware of making broad statements that are supposed to be true in all
cases. The one above is not.

Bill, W6WRT

One statement that IS True, and has been around "Forever":

Ground is not Ground, the World Around........


Me and RF Ground, is not Ground Ground........

As was pointed out before and mentioned by someone else, if the antenna
is mounted so as to be fed by a feed-line running at ground level AND
fed at this low point (coax probably best in such close proximity to
"ground ground")--and a set of rf grounding radials emanate in all
directions from this feed point (but just below ground), BOTH EARTH
GROUND and RF GROUND are at or "are very near" exact points.

For most other situations which come to mind, your statement is true.

JS

What is RF ground?
 

Bill Turner wrote:
ORIGINAL MESSAGE:

On Sun, 12 Nov 2006 15:14:49 -0000, "Dave" wrote:


but rf doesn't flow 'into the earth'

------------ REPLY FOLLOWS ------------

Beware of making broad statements that are supposed to be true in all
cases. The one above is not.

Bill, W6WRT

Bill,

The broadest and most general statement I made in my post was "All real
world implimentations of "RF ground" are less than perfect". I take it
from your negitive post that you disagree with this point.