Does height above Earth effect the common mode current response?

[BOOTY MONSTER]

I must have missed the point you were making when you posted about the Maco GPK, or I didn't see it at all.

If the radials, in this case work like you suggest, then your comments about Solarcon makes good sense. I can't remember what-does-what with radials on the Imax, but I do know for sure radials work well to raise and improve the look of the match with a 1/4 wave radiator.

just to clarify ..... he didn't use the boomer gpk , he said he used ground elements from a maco 58 . the 58 has 104 inch ground elements . the boomer gpk has 84 inch elements using maco's assembly guidelines . they're 12 inches longer than the 72's from solarcon and horizontal like the 58 rather than sloped .


Maco Assembly Instructions

just being picky/clarifying .

 

[Marconi]

Thanks.

I brewed a 5/8 with shortened radials, but found it not to my liking. I felt I could tell it was less a performer than the longer radials models I had made. Much less receive, not hearing at all, or hearing as well stations I had heard before. The problem with such a comparison for me is that a homebrewer might not make so good an antenna in the first place so the performance difference is owed to the poor construction more so than the potential variables.
The same may be said of any antenna I've made, however, with the amount of time I've spent building, tuning, and adjusting on the majority of them I don't accept that as the case.
That particular antenna went together, accepted the short radials, tuned to low SWR, and flew into the air. I didn't like what I didn't hear, and brought it down.

The point is, I wondered if there was a more detailed test available between us than my own quick trial.

Homer, I tried the same thing on my I-10K, just to see if it would work without radials, but it was no-way-no. I also tried it shortened with just the first two sections, and it was still no-way-no.

This was a long time ago and maybe I saw these results the same as you.

So, I had the thought the I-10K and other 5/8 waves that were similarly built and matched...probably would not work well with no radials or with shortened radials. But, just to be clear after my testing the Imax, I figured the Imax was different from other 5/8 waves, and maybe that had to do with the matching device used, even though it was just my thinking.

I have re-read most of this thread. I'm hopeful that I didn't misunderstand what antenna SW was talking about...when I said "...I didn't understand how SW would know..." in response to BM's post. BM, made and edit to a word in this post making a change to the word "2000's" that originally was noted as "W's" or it could have been just the opposite. I see it both ways, and I have no idea what SW saw.

It's fine with me for guys to do and edits, but I may owe SW and apology since I was thinking about an Imax, and maybe he was talking about another antenna that BM referred to as "W's". I'm still not sure.

I also see SW talking about a Maco radials, and I think there is another maker of this type of 5/8 wave, and maybe that is what BM was referring to when he used the word "W's" in his post. Maybe SW understood that short reference and was not talking about an Imax at all.

So, Shockwave if I got your remarks wrong, I apologize.

 

[BOOTY MONSTER]

.......... The S-827 is a good antenna. At the same time, the Penetrator is a bit better with its longer radials. The differences in gain and CMC are small but worth it to some.

did sirio ever fix the problem with the coil going open circuit from the vertical on the 827 ?

 

[Marconi]

just to clarify ..... he didn't use the boomer gpk , he said he used ground elements from a maco 58 . the 58 has 104 inch ground elements . the boomer gpk has 84 inch elements using maco's assembly guidelines . they're 12 inches longer than the 72's from solarcon and horizontal like the 58 rather than sloped .


Maco Assembly Instructions

just being picky/clarifying .

Booty you were a step ahead of me. I was being picky too.

 

[BOOTY MONSTER]

OGP , you've been ahead of me so many times that my turn finally came up

Thanks.

I brewed a 5/8 with shortened radials, but found it not to my liking. I felt I could tell it was less a performer than the longer radials models I had made. Much less receive, not hearing at all, or hearing as well stations I had heard before. The problem with such a comparison for me is that a homebrewer might not make so good an antenna in the first place so the performance difference is owed to the poor construction more so than the potential variables.
The same may be said of any antenna I've made, however, with the amount of time I've spent building, tuning, and adjusting on the majority of them I don't accept that as the case.
That particular antenna went together, accepted the short radials, tuned to low SWR, and flew into the air. I didn't like what I didn't hear, and brought it down.

The point is, I wondered if there was a more detailed test available between us than my own quick trial.

i had the same results trying shorter ground elements ........ i tried four 1/8wl horizontals and four 1/8wl sloped .

i'm not as confident as homer about taking builder error out of the equation , but homers having similar results makes me feel more confident that i wasn't too far off .

 

[HomerBB]

Marconi, I have used two different masts for a lot of testing/comps.
I thought about mentioning results I've had on them with respect to the RF issues, but thought my problems were not really related to CMC on the mast nor the coax, but was a proximity issue. I did not want to muddle the pool of thought.

The tip-over mast as an upper metal mast that does not touch the earth, so unless I provide that contact otherwise it is essentially ungrounded. I do not experience any issues with antennas on this mast. The other mast at the end of the house does descend to the earth. No matter which antenna I put on it I see some RF activity, even when I use a choke and well shielded coax. I have been able to reduce the proximity effects within the house/shack by raising the antennas higher up at that location, using a very well constructed choke, and the best coax I own, but that was not conclusive enough to provide proof it was CMC. When I moved the same antennas to the other mast farther away I gained the best results telling me my issue was RF going directly into the TV and PC speakers.
One might think it was some multiple of coax length that had the differing effects, but no. Either of those antenna masts were outfitted with similar length coax, about 80' long.

The antennas in the attic can completely freeze up my PC in the shack/garage when I use them requiring a restart to get it back online. Proximity.

 

[HomerBB]

Booty, I do not want to divert this thread into a discussion about the functions of a set of radials on a monopole antenna. It has proven to be inflammatory in some circles, or at least unpopular.
However, the radials are more than a coax/mast de-coupler with respect to CMC. and CMC is the basis of this thread.

Suffice it to say that I believe the need for a full set of radials on a monopole relates to the principles that describe a counterpoise. Regardless of whether folks use the terms groundplane and counterpoise interchangeably, there is a point of departure between the two that is lost on most, but distinguishes their function and meaning in the realm of RF energy applied to antenna systems. Neither Wikipedia nor Websters has a clue. What either of us may have experienced wasn't about CMC, but about a fully developed antenna system. I will venture to say that as close to the ground as you had your 5/8 with shortened radials the antenna was most likely so hopelessly deficient in radial system that to expect much more than what you felt you were getting was asking more than it could deliver. At the time you were experimenting with that set up I didn't have enough understanding of these things to have contributed to that point.

It is the shortened GP radials 5/8 that I did not take a long time fine tuning that causes me to reserve passing judgement on short radials owing to my experiences. That one would require more time and observation over time.

 

[Marconi]

Booty, I do not want to divert this thread into a discussion about the functions of a set of radials on a monopole antenna. It has proven to be inflammatory in some circles, or at least unpopular.

Ah come on Homer, I’ll still think you’re popular even if I might disagree.

However, the radials are more than a coax/mast de-coupler with respect to CMC. and CMC is the basis of this thread.

Suffice it to say that I believe the need for a full set of radials on a monopole relates to the principles that describe a counterpoise. Regardless of whether folks use the terms groundplane and counterpoise interchangeably, there is a point of departure between the two that is lost on most, but distinguishes their function and meaning in the realm of RF energy applied to antenna systems.

Tell us what’s on your mind Homer. This sounds like the way that W8JI talks sometimes, saying the words leaving us to assume the meaning. This thread is not limited just to CMC. I’ve talked about height, feed line length, modeling, Eznec, and maybe a few other topics. Talk to us.

Neither Wikipedia nor Websters has a clue. What either of us may have experienced wasn't about CMC, but about a fully developed antenna system. I will venture to say that as close to the ground as you had your 5/8 with shortened radials the antenna was most likely so hopelessly deficient in radial system that to expect much more than what you felt you were getting was asking more than it could deliver. At the time you were experimenting with that set up I didn't have enough understanding of these things to have contributed to that point.

Don’t depend on Wikipedia, as I understand, it is editable somehow. Webester purely looks at the root definition or a few variations in common use.

It is the shortened GP radials 5/8 that I did not take a long time fine tuning that causes me to reserve passing judgement on short radials owing to my experiences. That one would require more time and observation over time.

Don’t wait too long Homer, I’m getting older every day, and you’re the guy.

 

[HomerBB]

Marconi, I appreciate the openness you invite into this thread.
However, I started a thread on the forum about the counterpoise. A few interested folks participated. Even among we who did some expressed some variety of thought that reflected a limited interest in the subject to the point of trivializing the subject. Several I hoped would participate chose not to do so. I accepted that decision and moved on.
I do not think some who know things on some levels know much about the subject, or else dislike untangling the cords of time.

But, if it helps, what I was saying is simple.
Radials do more than decouple the mast and feedline.
Doc calls this other function - "the other half", yet, IMO, that falls short of a full explanation of what the meaning of counterpoise is.

What I said to Booty is that at the height his antenna was mounted it was insufficiently supplied by the radial size he used. Why? At that height it would require a large enough set of radials to provide a capacitive integration WITH the earth to make the antenna as efficient as he may have hoped.
A Counterpoise is designed to integrate the antenna with the earth by forming a capacitor between itself and the earth. It looks like a GP, and has functionality similar to a GP, but is not a decoupling device in this case, but just the opposite.

There is a point as we raise an antenna in height above the ground that the radials can no longer act as a capacitor plate with the earth in the same way it has down low due to the distance above the earth. At this point in height the radials begin to predominate as a Groundplane acting now as the substitute for the earth, or artificial ground, as the other half, and as a decoupling device for the for the coax and mast.
It is my opinion that the size of the radials network has a bearing on the performance of the antenna at every height, when low, when it may in fact be acting to couple the antenna to the earth, and high, as an artificial substitute for the earth decoupling from natural earth taking its place. When it is small it is a less proficient device. In some of my reading a case has been made for the activity upon the radiating energy from the antenna by the groundplane that says its size will work more favorably when its distance out from the vertical increases. Granted, the size of the radials is smaller as our height increases, but that doesn't mean we can just shorten them to the point of nothing and expect an efficient system.

To me one of the most common uses of this confusion is in mobile installations. Rightly it is said that the automobile provides the other half. Wrongly it is said the automobile is the groundplane. The automobile provides the other half by forming the counterpoise that provides a capacitor with the earth beneath the automobile. To me, this is why antennas mounted on top of the most central point of the mobile's bulk are the most successful. Clearly the automobile body is heavily disproportionate in size to the simple 1/4 wave mobile antenna, so what is occurring is not merely a matter of the other half in a purely physical sense as we seem to see with a dipole where both halves are equally sized. It is the work of the counterpoise, the combined coupling of the antenna system - antenna and mobile, in point of this point of discussion - with the true groundplane, the earth. Frankly, in my opinion, the automobile is not the same thing in a mobile setup as the radials system on a raised 5/8 wave antenna at all. For that matter, neither is the buried radials system of a ground mounted antenna the same as a counterpoise that is not connected to the earth physically, but raised to heights conducive to forming a capacitor with the earth. Is this distinction really important to understand? Apparently not. After all, antenna myths thrive on ignorance, and ignorance sells antennas, and selling antennas is important.

There is some complexity to this that even what I have written will confuse some. I can not help that as I often look to discussion to unravel and retie the twisted knots of my thinking.

There are nuances to understanding some things that take a lot of reading and reading again, and then clearly explaining them is still not easy. I have no doubt some of what I have written will be challenged, questioned, and picked apart. That's good. On the other hand, I have some doubt of that, as this subject is not very popular.

 

[Marconi]

Homer, I don't think I posted on that thread, because I don't understand enough of the neuances involved, and in trying to check the subject out on the Internet I find most of the topics are just further debates on how and when the word counterpoise is to be used correctly.

When you mentioned it here, I recalled the subject at once, but I didn't recall that you posted it.

IMO, the term is couched in science and physics, but is a suitable enough term to be broadly used in a lot of situations. I did find one statement that seems to fit the word, "The state of being in equilibrium," but in that case it would suggest a dipole to me, and not a vertical with radials.

So, it gets a little confusing and does not seem to me to fit the way it is ordinarly used in discussions on vertical antennas and radials.

 

[Marconi]

Booty Monster, your big images don't make it easy or enjoyable to read these posts.

I can send you a much smaller image of this picture that you can store and post when you need it.

 

[HomerBB]

Homer, I don't think I posted on that thread, because I don't understand enough of the neuances involved, and in trying to check the subject out on the Internet I find most of the topics are just further debates on how and when the word counterpoise is to be used correctly.

When you mentioned it here, I recalled the subject at once, but I didn't recall that you posted it.

IMO, the term is couched in science and physics, but is a suitable enough term to be broadly used in a lot of situations. I did find one statement that seems to fit the word, "The state of being in equilibrium," but in that case it would suggest a dipole to me, and not a vertical with radials.

So, it gets a little confusing and does not seem to me to fit the way it is ordinarly used in discussions on vertical antennas and radials.

Exactly why the term is unpopular as a subject of discussion, IMO, and why it ought to be discussed. We argue over the angle of a radial with feverish pitch, but when something comes along that is really confusing and could use an analysis through discussion it is not a favored subject.

Oh well. Can't win them all.

I think you may have made a post or two. I didn't keep count.

 

[Highland Ranger]

Interesting thread. Any conclusions? Can we summarize?

-> CMC, causes a feedline to radiate like an antenna and is a cause of RFI.

-> Monopole antennas like the IMAX 2000, feed length, grounding and height off the ground impact CMC. But no definitive answer as to how to reduce CMC.

-> Switching to a non-monopole design should reduce CMC but may not depending on installation

Are these statements correct? Anything else we can add?

(By the way - agree with the statement about the picture - anyway to get the forum software to limit the picture size - real pain to read the thread.

 

[Marconi]

Homer you posted a link in your thread on the counterpoise, but it no longer works. Was it a link to a Cebik report?

If not, here is one from Cebik that is in the public domain. It discusses the counterpoise issue, and common mode currents on the feed line is also listed in the topics.

Counterpoises, Capacity Hats, and A Standard

 

[HomerBB]

It was Cebik. It was about counterpoise. Not the one you found, although I will read that one soon.

This is the one I linked:

Counterpoise - LB Cebik