The whole truth, and nothing but the truth - Counterpoise

[HomerBB]

I think the vehicle subscribes to Laport's/Cebik's definition of the counterpoise quite well:

"A vehicle is not a ground plane, but rather acts like a capacitor between the antenna, and the surface under the vehicle which acts as the ground plane. Since the surface in question is a poor conductor of RF, ground losses occur." - k0bg

Ground Plane Notes

and

"One very important point needs to be made at this point. A vehicle is not a ground plane, but rather it acts like a capacitor between the antenna and the surface under the vehicle which acts as the ground plane." - k0bg

Antenna Efficiency


"The counterpoise is an insulated net of radial wires assembled above the ground to form a large capacitance with the ground." - Laport/Cebik

Counterpoise?

 

[KM3F]

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.

 

[W5LZ]

And to add another variable into this mess, the 'size' of the 'TOH' or 'groundplane' becomes less important with vehicles depending on the frequency of use. At HF that capacitance with 'dirt' certainly does make a difference. At VHF/UHF it becomes less important/effective/affective since the vehicle's metal body is plenty large enough to work for that 'TOH'.
- 'Doc

 

[The DB]

I haven't had a chance to read you linked post yet, as I am about to leave to go camping that will have to wait until I get back Sunday...

Thanks for commenting, however, if you read the link I posted above presenting an article written by L B Cebik it might provoke you to more thought on the subject . . .
It certainly did that for me.

Geez, I said I would read it didn't I? Give me a chance...

You were correct, and it did provoke thought. After reading the article and catching up on the debate I'm not so sure that everyone who posted since I did has read the article.

It does explain a few things, including how in the modern day everyone seems to have their own often wildly different definition for the term. It is also interesting to note where the term came from and the fact that it had nothing to do with antennas. Also of note is the fact that its original use in Amateur Radio was limited to the 160 Meter band, a band that we still don't fully understand the propagation of which today.

The closest thing to the original use in CB would be mobile antennas. The car itself would act as the counterpoise. I know there has been discussion on this, I think the article may have added some confusion near the end when it talks about a current use some have used in mistaking the other half of a dipole antenna as counterpoise. So does it matter that this counterpoise radiates? The article never specifically said, but it seems to me that the many radials used for the capacitive coupling to the ground would also radiate, thus making a counterpoise one form of "The other half" of the antenna.

Question 1) Is it really relevant to 11 meters? Is it limited to 160 Meters and lower bands as the the article states, or is it more universal, or irrelevant in radio all together?

And depending on that answer.

Question 2) How should we define it today? Should we use the original definition or use something that would fit the more current and less consistent uses of the word?

I'll come back later and read it again.


The DB

 

[HomerBB]

Didn't mean to be mean

I agree that after reading the materials provided it seems that some who've replied are just sticking to the way they've always thought instead of commenting to the articles.

As for question 1, yes it is relevant to eleven meters. Esp since there are so many 11 meter operators out there experiencing a variety of results from identical antennas who fail to understand how and why these differences occur. Giving general answers to specific issues leaves too much misunderstanding, and too little education in play. I know you question about relevance is directed to whether this is an issue at 11 meters. Because of well reasoned materials I've read, and due to the simple reality that 11 meters has to deal with contextual issues such as ground losses, sudden shifts in SWR with no changes to installs, particularly mobiles, and differences in same antenna experiences with base installations so prevalent, I think the issue is fundamental to knowing what is at work, and how to fix it when necessary.

Question two - apply it right. Quit perpetuating information that rides a wave of misconception and ignorance. Why would we want to attempt to help some one find their way to Georgia by way of Minnesota, Idaho, Nevada, and then maybe they finally ask someone who knows that sends them right past Texas where they started via I-10 into Georgia?

I guess I am too much of a purist . . .

 

[The DB]

I am continuing the numbering of questions as opposed to starting over to avoid potential confusion later.

As for question 1, yes it is relevant to eleven meters. Esp since there are so many 11 meter operators out there experiencing a variety of results from identical antennas who fail to understand how and why these differences occur. Giving general answers to specific issues leaves too much misunderstanding, and too little education in play. I know you question about relevance is directed to whether this is an issue at 11 meters. Because of well reasoned materials I've read, and due to the simple reality that 11 meters has to deal with contextual issues such as ground losses, sudden shifts in SWR with no changes to installs, particularly mobiles, and differences in same antenna experiences with base installations so prevalent, I think the issue is fundamental to knowing what is at work, and how to fix it when necessary.

Question 3) On 11 meters, how would we determine the optimum or most efficient height for a counterpoise setup, and how would we determine the maximum effective height? Or for that matter the minimum effective height should one exist?

As was mentioned:

At HF that capacitance with 'dirt' certainly does make a difference.

I'm guessing this would change with frequency. I am also guessing that that the quality of the ground would make a difference as well, as a more conductive ground would naturally allow for more capacitance and thus allow for similar results with a smaller radial system. A more conductive ground would also allow a radial system to be further away (higher if you will) and still have the needed capacitance between ground.

Question 4) What happens when it rains? That would change the conductivity of the ground beneath the radial system would it not? Would it also change the tuning of said antenna? If I were to build such an antenna would it be worth my time top stabilize and/or potentially increase the typical conductivity of the ground in question?

Question two - apply it right. Quit perpetuating information that rides a wave of misconception and ignorance. Why would we want to attempt to help some one find their way to Georgia by way of Minnesota, Idaho, Nevada, and then maybe they finally ask someone who knows that sends them right past Texas where they started via I-10 into Georgia?

I guess I am too much of a purist . . .

I agree with this. I have been applying it incorrectly, and admit it. I will be more careful in the future. The thing here is those newer listed publications in the article and many others that are also using it incorrectly, and often differently from each other. People can simply point to any of them to say that their use is correct. The current version of the ARRL Antenna Book (22'nd edition) is no different, although it only mentions it once according to the index and basically calls it the ground plane for an elevated monopole antenna.

I also tend to be a purist.

Question 5) Is there a recent publication that uses the term correctly?

Question 6) Should its use only apply to monopoles? Figure 1 in the article clearly shows it being used with an antenna that is not a monopole, although from shortly thereafter it is almost exclusively used with (and perhaps for) monopoles with maybe one exception.

Question 7) Is there a similar article on the use of the term "Ground Plane? As it is related but not directly to counterpoise and in some peoples definitions the two are equivalent. I have also noticed different people using different definitions for the term, although not as wildly different as what is used for counterpoise. I am curious how that term came to its current meanings as well. I bet it is also commonly misunderstood and misused.


The DB

 

[The DB]

A web page I just stumbled across but may be relevant to this discussion.

Counterpoise - what does it mean?


The DB

 

[The DB]

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

 

[HomerBB]

I will try to get back to you on this later when I have the time.
It does seem there are but a narrow number of folks willing to address this issue.
Perhaps they have come to the same conclusion as VK10D, and had rather not mention it than clarify its usage when using it.

That would be sad . . .

 

[Robb]

Funny that no one used the term 'radiation pattern' and its effects with the 'counterpoise'.
Oops!

 

[hookedon6]

.... 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.

actually, many AM stations looked like an auto junk yard,...........

junk cars parked front to back below the antenna, one guess why

 

[roadrage]

It does seem there are but a narrow number of folks willing to address this issue.

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

 

[binrat]

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

Then sit back, grab a beer and learn.

 

[The DB]

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

It is a highly misunderstood term.

I am surprised at how few people are posting as this is a more technical forum than others out there and their are some very knowledgeable people that frequent these boards. I was hoping for more...

I have noticed that there are quite a few views on this thread for being around for such a short time. Perhaps people are watching to see what comes. I think it exposed enough to show how little people actually know about a very commonly used term in the radio world.

I would like to see more people take this on, and I think the op would like to see more as well. There are those on here that know much more than I do and I am not sure what to make that most of them have yet to post anything here.


The DB

 

[HomerBB]

I am continuing the numbering of questions as opposed to starting over to avoid potential confusion later.



Question 3) On 11 meters, how would we determine the optimum or most efficient height for a counterpoise setup, and how would we determine the maximum effective height? Or for that matter the minimum effective height should one exist?

Some of these questions were those I hoped others deeper in Antenna theory, and history, might be able to help us sort out. However, if I were to guess taking the optimum distances above earth for 160 meters from the aforementioned reading of "3.3 to 4.9 feet" then extrapolating the numbers from there perhaps only about to 2.7" to 4". Maybe someone knows for sure.

As was mentioned:

I'm guessing this would change with frequency. I am also guessing that that the quality of the ground would make a difference as well, as a more conductive ground would naturally allow for more capacitance and thus allow for similar results with a smaller radial system. A more conductive ground would also allow a radial system to be further away (higher if you will) and still have the needed capacitance between ground.

Question 4) What happens when it rains? That would change the conductivity of the ground beneath the radial system would it not? Would it also change the tuning of said antenna? If I were to build such an antenna would it be worth my time top stabilize and/or potentially increase the typical conductivity of the ground in question?

I should expect so.

I agree with this. I have been applying it incorrectly, and admit it. I will be more careful in the future. The thing here is those newer listed publications in the article and many others that are also using it incorrectly, and often differently from each other. People can simply point to any of them to say that their use is correct. The current version of the ARRL Antenna Book (22'nd edition) is no different, although it only mentions it once according to the index and basically calls it the ground plane for an elevated monopole antenna.

I also tend to be a purist.

Question 5) Is there a recent publication that uses the term correctly?

Question 6) Should its use only apply to monopoles? Figure 1 in the article clearly shows it being used with an antenna that is not a monopole, although from shortly thereafter it is almost exclusively used with (and perhaps for) monopoles with maybe one exception.

Question 7) Is there a similar article on the use of the term "Ground Plane? As it is related but not directly to counterpoise and in some peoples definitions the two are equivalent. I have also noticed different people using different definitions for the term, although not as wildly different as what is used for counterpoise. I am curious how that term came to its current meanings as well. I bet it is also commonly misunderstood and misused.


The DB

These questions are yet to be answered.