The whole truth, and nothing but the truth - Counterpoise

[HomerBB]

I think I was putting to much effort into this. Thinking this through again from the definition of the word itself as a starting point.

Counter is a way of saying oppose or to oppose
Poise is another word for balance

So the word itself means to oppose with balance. When it comes to RF that translates to cancel, as that is what an opposite yet balanced RF signal would do to another.

If you look at a monopole with a flat even number radial system the radials opposite each other radiate RF in such a way that they balance and oppose each other. Does this not fit the definition of the word counterpoise? So here it does not relate to the effects of a radial system has on the antenna, but the effects the radial system has on itself.

The direct translation of the word does not say nor imply anything about capacitive coupling, so using it as only meaning a raised radial system that is capacitively coupled to the ground would not fit the definition of the word. Remember, it's origins are from old AM Broadcast theory. AM broadcast even today use huge antennas usually mounted near the ground. There would have been no need to have meaning beyond such an antenna system as it was likely cost prohibitive to raise it any significant amount above ground. Such a setup near the ground with its capacitive coupling would have lessened the ground losses thus making the antenna more efficient.

Should we limit this old use of a word used with antennas that were much more limited because of their size to other frequencies that are in use, most of which are on orders of magnitude higher in frequency and thus are able to use much smaller antennas that can be raised quite high? Does the meaning of the word itself still apply even there is little to no capacitive coupling because of the possible heights of these antennas?

At this point I have to say yes.

Reading the article I changed my mind on what counterpoise meant when referring to antenna systems, now I have changed my mind again to something similar to what I originally thought, although with a bit more understanding of the definition of the word itself. In other words, I may have been mostly right but for the wrong reasons.


The DB

Naturally, you can come to any conclusion you are comfortable with, but I find that it is just easier to take the fundamentally engineering term and break it down by its etymological parts and become victim to the same error causing process that has plagued the term. In other words, just because the parts of the word can mean such a thing, it doesn't necessarily hold that such an interpretation of the term as opposed to how it was originally employed is accurate.

I might add that this whole thing of opposing radials cancelling out each other tends to add frustration to the discussion. After all, if such be the case how would one explain the need of it at all. It would cease to be functionally relevant and as good as none at all. Perhaps I am missing something.

In my studies of equal and balancing elements, as in a dipole, each is on opposite cycles of positive and negatively charged currents at the frequency of use so that there is no cancellation of each other, but a forcing of the current outward as radio frequency waves. In the case of a set of GP radials the entire radial network act as the opposing part and I believe all of them are charged the same as each other at the same time.
I think you can see this when you realize that the GP radials are in their entirety connected to the antenna system by way the braid of the coax, or 1/2 half the feedline. If cancellation were an issue in such an arrangement even a dipole would not work, no?.

I think the idea you brought over from the article you linked is flawed in that respect.

Maybe I'm wrong and neither my GP antennas, nor my dipole I talked to Hawaii with today do not work.

 

[HomerBB]

I would be glad to chime in here, but this is just over my head.

Mine, too.
I am going way out on a limb here, but there has to be something to learn about the truth regarding the counterpoise, a groundplane, and the distinctions and similarities between them. At least it seems there used to be.

 

[The DB]

I think the big and possibly only difference between your line of thought and my current line of thought is the capacitive coupling to ground. You are thinking that it is a vital part of the proper use of the term counterpoise when it comes to antennas and I am thinking it may not be. I think on most other points we actually still agree.

It is not that I think that your point of view is wrong, I simply don't have any hard evidence (or circumstantial for that matter) either way, and until I do it is a matter of opinion, a history that was possibly based on a point of view, and a mass of inaccurate and contradictive uses of the word. The most solid thing I have to go on here is the literal definition of the word so I choose to use that.

I would love to read several of the books in question or interview their authors to get a more complete viewpoint. Other books from the time periods especially the earlier ones would be useful as well.


The DB

 

[HomerBB]

Fair enough. I'd like to see folks add the weight of their understanding and experience.
If RF science is reliable, then the answers should lie within a discussion of the same.
I am in neutral, as opposed to a premature (from my point of view) landing upon a position supported by no more than just because it feels good so far. I am not mocking you, I am just calling tradition out into the middle of the street at high noon.

A story: When my daughter was small she fell through an unfinished floor of a two story house and broke her jaw on the way down. Her dentist took X-rays and sent us to see a specialists. His name was Hollier. Hol yer, right?
Nope. O yay.

 

[HomerBB]

I think the big and possibly only difference between your line of thought and my current line of thought is the capacitive coupling to ground. You are thinking that it is a vital part of the proper use of the term counterpoise when it comes to antennas and I am thinking it may not be.
The DB

You may be right, but it is hard to know without more info, and perhaps a healthy dose of reasoned discussion at so late a point in time . . .

 

[The DB]

I just found a .pdf version of the book "Radio Antenna Engineering" by Edmund A. Laport, or so the website claims.

HomerBB, your point of view seems to have been redeemed.

It seems that the capacitive coupling with the actual ground is an important and vital component in a counterpoise or at least was. However, the quoted paragraph from this book is in the Low Frequency section.

I will do some more research on this 575 page book, but not tonight...


The DB

 

[HomerBB]

I'll look it up.
Share with us when you can.

 

[roadrage]

You may be right, but it is hard to know without more info, and perhaps a healthy dose of reasoned discussion at so late a point in time . . .

That is one of those things. Everyone has a distinct opinion, but which one to choose as fact? I could tell my youngest son that 2+2=5 and the kid down the street tells him that 2+2=3, and at school he is told by his teacher that 2+2=4. So he is confused. Most people would just pick the person whose knowledge they trust the most. They would "know" what the answer is. But what if they have placed their trust in the wrong person? I am sure my son would believe me over his friend or teacher. But he would have chosen incorrectly.

The wise thing to do is learn the value of the numbers used, then the answer can be figured out and he'd know for himself which is correct. And even though his answer is now correct by fact, in the eyes of others who don't know the values of the numbers, he would be seen as just another opinion.

I think that most people are satisfied with just having an answer they believe to be true rather than spending the time to have the knowledge to determine its factuality. Obviously antenna theory isn't as simple to learn the values as simple numbers. Therefore it is much more difficult to say for certainty which is the correct terminology. To make things more complicated, unlike numbers with given values that will never change, terminology often changes over time. Definitions of a word can evolve and take on a meaning that may have relation to what was known previously, but still changes.

I like this thread.

 

[The DB]

The quoted paragraph in HomerBB's link is the entirety of the text on counterpoise minus one sentence in the Low Frequency portion of the book. There is one more section that includes the term counterpoise, and that one is referring to a Medium Frequency antenna which is mounted on top of a building.

Radio Antenna Engineering, Chapter 2 Section 8, Broadcast Antennas on Buildings, Paragraph 2

The ground terminal must be constructed on the roof. If the roof is of sufficient area, a symmetrical counterpoise of 20 or more radial wires (insulated from all supports with light duty insulators) may be a satisfactory ground. Since these conditions are seldom present, the system shown in figure 2.32 may be used. This is an adaptation of the Brown very-high-frequency ground-screen antenna. From two to four horizontal wires are centered under the radiator, each having an electrical length of one quarter wavelength when loaded with inductance as shown. Each wire, when tuned naturally or with inductance, brings a virtual zero-potential point in the center which is taken as the ground point in the system. The full wire length can sometimes be used by allowing the excess length beyond the roof limits to hang down along the side of the building, properly secured and insulated.

This paragraph mentions using a counterpoise system on a roof. It makes no mention of the height of the roof in question. Depending how how this is read it can challenge the capacitive coupling mentioned in the paragraph quoted in the linked Cebik article. I am not saying that it does, just that it could be read that way. It also talks about an antenna setup very similar to a modern day elevated ground plane antenna in almost the same breath. Again I am hesitant to take this as direct proof, but I have to assume at the very least that they are related.

Between this and the paragraph Cebik quoted this is the extent that counterpoise is mentioned in this book. When talking about ground mounted Medium Frequency antennas the radial system is either referred to as on ground or in ground, neither of which I think apply to this thread. Aside from being on a building as the above paragraph mentions, there is no other mention of an elevated radial system, with or without capacitive coupling to ground.

There is no additional information to be had in the High Frequency section, as all but one of those antennas are horizontally polarized. The one vertically polarized antenna is an inverted v. It does talk about ground losses and the conductivity of the ground some, but nothing even close to a raised radial system.


The DB

 

[The DB]

I just happened to be looking through my ARRL Antenna Book 22'nd Edition and happened across an interesting diagram. Take a look at this diagram.

Does it not show exactly what Cebik was trying to say, and what is described in Laport's book?

The top diagram is for a buried ground radial system, the bottom diagram is what drew drew my attention.

The caption for the figures is as follows. Subtext is in {} as I can't easily reproduce it.

ARRL Antenna Book, 22'nd Edition Chapter 9 Page 13

Figure 9.19 - How earth currents affect losses in a short vertical antenna system. At A, the current through the combination of C{E} and R{E} may be appreciable if C{E} is much greater than C{W}, the capacitance of the vertical to the ground wires. This ratio can be improved (up to a point) by using more radials. By raising the entire antenna system off the ground, C{E} (which consists of the series combination of C{E1} and C{E2}) is decreased while C{W} stays the same. The radial system shown at B is sometimes called a counterpoise.

Also posting a paragraph from the same page that refers to those diagrams.

ARRL Antenna Book, 22'nd Edition Chapter 9 Page 13

When a buried-radial ground system is used, the efficiency of the antenna will be limited by the loss resistance of the ground system. The ground can be a number of radial wires extending out from the base of the antenna for about 1/4 wavelength. Driven ground rods, while satisfactory for electrical safety and for lightening protection, are of little value for an RF ground for a vertical antenna, except perhaps in marshy or beach areas. As pointed out, many long radials are desirable. In general, however, a large number of short radials are preferable to only a few long radials, although the best system would have 60 or more radials longer than 1/4 wavelength. An elevated system of radials our ground screen (counterpoise) may be used instead of buried radials, and can result in an efficient antenna. Figure 9.19 and Figure 9.20 illustrate the differences between burial and elevated radial systems and counterpoises. The reader is directed to the chapter Effects of Ground for a discussion of ground plane radial systems and counterpoises for vertical monopole antennas.

OK, looking up the Chapter called Effects of Ground. Hey look, I found something else.

ARRL Antenna Book, 22'nd Edition Chapter 3 Page 10"

There are different ways to install wire ground systems: the wires may be buried in the soil a few inches or lying on the ground surface or elevated several feet above the ground or even some combination of these. In addition, in elevated systems there may be interconnections between the radial wires to form what is called a "counterpoise". Another possibility is to use a coarse rectangular mesh, either on the ground surface or elevated...

I have found still more but am out of time at the moment. Will read through and post more tonight.

Just think, a goldmine of information right under my nose, and this book's index item for counterpoise didn't point to any of it. I had to literally stumble across it on accident!


The DB

 

[The DB]

OK, here is some more, I think there is less additional than I originally thought...

ARRL Antenna Book, 22'nd Edition, Chapter 3 Page 18

Counterpoise Systems
In the early days of radio, operating wavelengths were in the hundreds or thousands of meters. Early on it was recognized that an elevated system of wires called a "counterpoise" or "capacitive ground" with dimentions much smaller then 1/4 wave length could be very effective. ... Rectangular counterpoises made with a coarse rectangular mesh were also very common. Amateurs have dome some experimental work on counterpoise systems.{10} On 80 or 160 meters the normal 1/4 wave length radial system may well be to large for many amateur locations so a counterpoise can be a practical option. However it is recommended the the proposed installation be carefully modeled and optimized before construction to avoid surprises.

That {10} was to point to a reference, they are referencing Doy, Frey and Mills, "Effecient Ground Systems for Vertical Antennas," QST, Feb 1983, pp 20-25

Chapter 3 seems to have multiple authors as it effectively says that a counterpoise is two different things. At one point it seems to be saying that a counterpoise is a radial system that is connected together on the tips and possibly elsewhere, to include a metal mesh. Later in a small section titled "Counterpoise Systems" it has the more traditional Laport like view if you will and actually called it a capacitive ground. This one also agrees with the text in chapter 9 that was quoted earlier as well as the diagram from chapter 9. Now that is a term I have just now come across, time to do more research...


The DB

 

[HomerBB]

I have heard the term capacitive ground before. At the time I apparently was not delving into this particular subject matter.
I appreciate your interest and contributions.

 

[The DB]

I have heard the term capacitive ground before. At the time I apparently was not delving into this particular subject matter.

I did a search on capacitive ground, the only things I seem to come up with related to antennas is a few RF bonding pages for vehicles.

I appreciate your interest and contributions.

Don't mention it, I learned the truth of a matter that I had wrong, along with 99% plus of others that also used the term. I just wish more people would have chimed in along the way. What happened to all those names on this forum who's opinions I respect?

I did a search on the other day and am amazed at some of the things people called counterpoise when it comes to antennas.

And sorry for the virtual takeover of the thread in the last two pages...


The DB

 

[HomerBB]

No problem. I have never owned a thread. It's a public forum.

 

[nav2010]

Look at it this way.
Take a dipole and mount it vertical.
It is a complete antenna.
Turn the bottom half horizontal, you still have a complete antenna.
Add 3 more same length horizontal elements and you still have a complete antenna.
This config is normally called a vertical ground plane right or wrong.
Shift to a mag mount 1/4 wave element in the center of an auto roof.
The mag mount element by it'self is still only one half of a system.
You could not set it on a big peice of cardboard and expect it to work.
The body with all the various shapes is the untuned ground plane. It is the 'plane' the driven element sets on.
The total area of the mag mount = one plate of a large area capacitor.
At the operating frequency, hopefully the capacitive reactance or X sub C between the mount and the roof is very low. Sometimes the paint type will have a large effect. Especially the mettalic looking types.
Any antenna system has an oscillating RF current between the two halves no matter how it's configured.
On a vehichle not only does the body work as the other half, the body/frame capacity to earth again the X sub C, plays a small part.
Going on, as you move, the steel rod in concrete is affecting the match to a small degree.
As you move, street lamp standards, road signs and other cars and truck keep changing the pattern response and the gain or loss of signal as you move, by phase additions and subtractions especially under weak signal conditon in the noise level area where it could be most noteable.
You need to have all or enough back ground for this subject to even begin to fully understand what you read from other tech sites or you often come to incorrect conclusions instead of well informed positions.
Ground plane, counter poise, radials makes little difference as along as you apply the correct 'thinking' to the specific configuration.
Good luck.

I'd call that a quarter wave ground plane.