ok so forget the palammar. what would be a good choice to isolate the feedline from the antenna ?????
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End-fed verticals and Ground Planes
- Thread starter Marconi
- Start date
In case you missed it, a while back I posted a thread entitled Another look at the Imax. There are links to some graphics that come from an article by W8JI
Maybe this article and the graphics will help you visualize the affects being discussed.
Maybe this article and the graphics will help you visualize the affects being discussed.
wich one of these
www.radio-ware.com/products/w2dui.htm
maybe this one will work better ???
users.erols.com/rfc/Choke%20Kit.htm
here is some interesting reaing on the efects of using and not using a balun
www.arrl.org/tis/info/pdf/8004019.pdf
wondering if changing to 9 foot ground radials woul be worth it aswell after putting on the balun ?? comes with 6 foot whips.
www.radio-ware.com/products/w2dui.htm
maybe this one will work better ???
users.erols.com/rfc/Choke%20Kit.htm
here is some interesting reaing on the efects of using and not using a balun
www.arrl.org/tis/info/pdf/8004019.pdf
wondering if changing to 9 foot ground radials woul be worth it aswell after putting on the balun ?? comes with 6 foot whips.
so then i'll ask this would my homebrewed end fed 1/2 vert. be any better with a ground plane? would that have to be isolated from the mast or not ? it already has an ugly balun about 2 ft. from the feed point and it's only 13ft. off the ground.
The way I read the information here is; these antennas need to have the right number of radials in order to do the job. I'm not sure I can tell you what that number is however. I think it has been said that four may be too few. I do not know how to evaluate this condition in order to determine the number.
So, I guess we have to first determine if we have currents on the feed line or mast by using the probe mentioned. Of course we need to have a suitable balun installed as well. Then we start adding GP radials until the currents on the feed line stop. I would like to know where on the system this measurement is made also.
The antenna needs the ground radials, because the current has to flow somewhere if not on the feed line. If there are no radials or not enough radials then the balun cannot work, as intended, by itself. The balun can only balances the feed point if there is a suitable counterpoise or ground path available for the currents on the feed line or mast. And if this counterpoise is not suitable, then the mast should not be connected to the grounded side of the antenna at the common point. I assume this point to be the area at the feed point or mounting bracket.
Long and short is RF, if you're not having TVI problems and/or the antenna is otherwise working to your satisfaction as is, then why go to all the trouble and expense. This is just an exercise in theory. These ideas may well apply in many cases to improve effectiveness, but all these no-ground plan antennas mentioned seem to work pretty well as they are. This is why and how the manufactures can build and sell them successfully every day.
This is just information, to get us thinking a bit when we hear the CB talk about the issue of GPK’s and such. You know the old story, “…I put tha’ GPK on my new ‘Wizzer’ and now I got stations a hunard’ miles out that I ain't never herd' before, and it stopped my TVI and noise too.”
So, I guess we have to first determine if we have currents on the feed line or mast by using the probe mentioned. Of course we need to have a suitable balun installed as well. Then we start adding GP radials until the currents on the feed line stop. I would like to know where on the system this measurement is made also.
The antenna needs the ground radials, because the current has to flow somewhere if not on the feed line. If there are no radials or not enough radials then the balun cannot work, as intended, by itself. The balun can only balances the feed point if there is a suitable counterpoise or ground path available for the currents on the feed line or mast. And if this counterpoise is not suitable, then the mast should not be connected to the grounded side of the antenna at the common point. I assume this point to be the area at the feed point or mounting bracket.
Long and short is RF, if you're not having TVI problems and/or the antenna is otherwise working to your satisfaction as is, then why go to all the trouble and expense. This is just an exercise in theory. These ideas may well apply in many cases to improve effectiveness, but all these no-ground plan antennas mentioned seem to work pretty well as they are. This is why and how the manufactures can build and sell them successfully every day.
This is just information, to get us thinking a bit when we hear the CB talk about the issue of GPK’s and such. You know the old story, “…I put tha’ GPK on my new ‘Wizzer’ and now I got stations a hunard’ miles out that I ain't never herd' before, and it stopped my TVI and noise too.”
Marconi,
First let me say that I'm not disagreeing with the facts in the article. But there are some things that have to be considered when relating the article to 'real life' antennas, and that's also pointed out in the article.
What I'm getting at is that the experiment was done at VHF/UHF, not at HF. It was also done under as 'perfect' conditions as is practical. The 'catch' is that (as was stated) objects in the near field affect radiation patterns, make changes that may/may not be benificial. One of those things that happen with all antennas.
So, the benifits of using a balun are variable depending on antenna location and mounting, as far as radiation patterns are conserned. And since there are other ways of correcting/reducing/eliminating currents on the outside of coax, a balun may not be the answer in all cases.
From experience, a balun on HF can cause some weird 'other' problems. The worst being that it can't handle what's being fed through it, resilting in a decrease in signal output. Two things affect balun performance the most, frequency of use, and power handling ability. Meaning that if the thing isn't designed for the frequency range/band of use, it just isn't going to be very good. Power handling ability is a fairly common knowledge sort of thing, right? I don't see any point in getting into that.
Another 'problem' today is that people tend to want things 'microscopic' in size, which just doesn't 'cut it' with baluns in most cases. (Or antennas, either, for that matter!) Baluns of appropriate 'size' are going to be noticable, which isn't always 'good'. At least at HF.
One thing that I've found with using baluns is that they tend to be another 'problem spot' at HF. Sometimes they are just more trouble than they're worth. My experiences with baluns are sort of dated, so they may be made 'better' today than a number of years ago.
This is just FWIW and something to think about...
- 'Doc
First let me say that I'm not disagreeing with the facts in the article. But there are some things that have to be considered when relating the article to 'real life' antennas, and that's also pointed out in the article.
What I'm getting at is that the experiment was done at VHF/UHF, not at HF. It was also done under as 'perfect' conditions as is practical. The 'catch' is that (as was stated) objects in the near field affect radiation patterns, make changes that may/may not be benificial. One of those things that happen with all antennas.
So, the benifits of using a balun are variable depending on antenna location and mounting, as far as radiation patterns are conserned. And since there are other ways of correcting/reducing/eliminating currents on the outside of coax, a balun may not be the answer in all cases.
From experience, a balun on HF can cause some weird 'other' problems. The worst being that it can't handle what's being fed through it, resilting in a decrease in signal output. Two things affect balun performance the most, frequency of use, and power handling ability. Meaning that if the thing isn't designed for the frequency range/band of use, it just isn't going to be very good. Power handling ability is a fairly common knowledge sort of thing, right? I don't see any point in getting into that.
Another 'problem' today is that people tend to want things 'microscopic' in size, which just doesn't 'cut it' with baluns in most cases. (Or antennas, either, for that matter!) Baluns of appropriate 'size' are going to be noticable, which isn't always 'good'. At least at HF.
One thing that I've found with using baluns is that they tend to be another 'problem spot' at HF. Sometimes they are just more trouble than they're worth. My experiences with baluns are sort of dated, so they may be made 'better' today than a number of years ago.
This is just FWIW and something to think about...
- 'Doc
Uh Oh!, "Wheel of fortune, on in 15 minutes!" never mind?
'Doc, I'm not sure about how the test was done, but you are right about real world experiences. I know that the problems mentioned here are not always terrible, but compared to some stories we all hear about the GPK being the solution, that beats all solutions, and how it brings this antenna alive when otherwise dead, I have to believe there is more to the issue. I think the article brought that out pretty well even if it was not scientifically perfect and that is what I was trying to bring to the discussion.
My point in the question was, will the GPK solve the problem of common mode currents. This antenn and others that are similar, depend on CMC to work in the design. To go even further, it is likely that most of the end-fed verticals we use in 11 meters that have ground plans really don't do a good job at stopping CMC either. Will the GPK really solve any of the problems that exist in its absence?
You know I asked you a long time ago if you could help us understand more by your help in modeling. I don't remember what happened, and I still can't do it successfully. When I read this article and saw the graphics, it gave me some idea, if true, what I suspected may be going on all along. I just had to wait some years to really find out. I wish I knew more and if I did I would try to explain it so folks could understand what I was suggesting.
'Doc, I'm not sure about how the test was done, but you are right about real world experiences. I know that the problems mentioned here are not always terrible, but compared to some stories we all hear about the GPK being the solution, that beats all solutions, and how it brings this antenna alive when otherwise dead, I have to believe there is more to the issue. I think the article brought that out pretty well even if it was not scientifically perfect and that is what I was trying to bring to the discussion.
My point in the question was, will the GPK solve the problem of common mode currents. This antenn and others that are similar, depend on CMC to work in the design. To go even further, it is likely that most of the end-fed verticals we use in 11 meters that have ground plans really don't do a good job at stopping CMC either. Will the GPK really solve any of the problems that exist in its absence?
You know I asked you a long time ago if you could help us understand more by your help in modeling. I don't remember what happened, and I still can't do it successfully. When I read this article and saw the graphics, it gave me some idea, if true, what I suspected may be going on all along. I just had to wait some years to really find out. I wish I knew more and if I did I would try to explain it so folks could understand what I was suggesting.
the fact that the tests were performed at uhf has no bearing on either power handling ability or frequency of operation. these are both directly related to the core type and permeability used for the frequencies and power levels in question. core saturation is a function of design and the core materials used. the big problem today in balun construction is dielectric isolation between input and output vs. construction cost and marketability. as far as i'm concerned no self-respecting balun manufacturer should be housing 1:1 current baluns in materials such as PVC. the lossy crap they use for filler in this stuff will dissipate almost 20% of applied power at middle-upper hf frequencies. i mentioned this somewhere else but allow me to expound. trace copper elements, carbon black and other filler materials virtually destroy the dielectric properties of PVC and is IMHO not suitable for proper and effective balun construction.
as to the problems created in the near field by surrounding objects and obstructions, an installation in the clear for at least a wavelength in all directions is mandatory and the inability of the operator to provide the proper environment along these lines will not be the subject of any of my discussion. if it's not clear for a wavelength in all directions with the feedpoint at least a wavelength above ground then it's time to move or put up with the shortcomings of the surrounding environment. the problem of interaction and coupling will only become worse as the antenna comes into balance, with few exceptions.
the number of radials used are much less important than achieving equal charge in the number of radials you do use and seeing to it that the total amount of charge in all of the radials is equal to the charge present in the main radiator, that total charge (in all elements, radiator and radials) being the equivalent of the total current presented at the feedpoint in direct correlation to the amount of power applied by the transmitter and the input impedance of the load, or antenna. all three are a function of one another, as expressed in the formula:
Zl = Pa / I2 or, load impedance is equal to applied power divided by the square of the current. in an example with 100 watts of applied power into a 50 ohm load, the current generated at the feedpoint is 1.414 amps @ 70.7 volts. 1.414 squared is 2. 100 watts of power divided by 2 = 50 ohms of load impedance. if you want to double check the calculation it's as easy as multiplying 1.414 X 70.7 = 99.9698 watts or 100 watts. P = I X E.
in a balanced antenna system under the conditions mentioned above we should have .707 amps of charge-as-current flowing in the main radiator and another .707 amps of charge-as-current total flowing in all of the radials present. we would also measure no charge-as-current on the outer shield of the feedline and on the supporting mast. this is perfect elevated ground.
since the total cancellation of the two opposing charges contained in the main radiator and the radial system is responsible for the generation of the ensuing magnetic field the importance of a balanced system begins to become evident. the elimination of common-mode-current is necessary to prevent gross field pattern distortion, uncontrolled TO angles and overall radiator inefficiency. total radiated power is the objective and it cannot occur when opposite but unequal charges exist on the two halves of the antenna. simply adding radials will not solve this problem.
as to the problems created in the near field by surrounding objects and obstructions, an installation in the clear for at least a wavelength in all directions is mandatory and the inability of the operator to provide the proper environment along these lines will not be the subject of any of my discussion. if it's not clear for a wavelength in all directions with the feedpoint at least a wavelength above ground then it's time to move or put up with the shortcomings of the surrounding environment. the problem of interaction and coupling will only become worse as the antenna comes into balance, with few exceptions.
the number of radials used are much less important than achieving equal charge in the number of radials you do use and seeing to it that the total amount of charge in all of the radials is equal to the charge present in the main radiator, that total charge (in all elements, radiator and radials) being the equivalent of the total current presented at the feedpoint in direct correlation to the amount of power applied by the transmitter and the input impedance of the load, or antenna. all three are a function of one another, as expressed in the formula:
Zl = Pa / I2 or, load impedance is equal to applied power divided by the square of the current. in an example with 100 watts of applied power into a 50 ohm load, the current generated at the feedpoint is 1.414 amps @ 70.7 volts. 1.414 squared is 2. 100 watts of power divided by 2 = 50 ohms of load impedance. if you want to double check the calculation it's as easy as multiplying 1.414 X 70.7 = 99.9698 watts or 100 watts. P = I X E.
in a balanced antenna system under the conditions mentioned above we should have .707 amps of charge-as-current flowing in the main radiator and another .707 amps of charge-as-current total flowing in all of the radials present. we would also measure no charge-as-current on the outer shield of the feedline and on the supporting mast. this is perfect elevated ground.
since the total cancellation of the two opposing charges contained in the main radiator and the radial system is responsible for the generation of the ensuing magnetic field the importance of a balanced system begins to become evident. the elimination of common-mode-current is necessary to prevent gross field pattern distortion, uncontrolled TO angles and overall radiator inefficiency. total radiated power is the objective and it cannot occur when opposite but unequal charges exist on the two halves of the antenna. simply adding radials will not solve this problem.
oh kay, after re reading this entire post, especialy the last 2 entries. a little light bulb in my head began to glow a little brighter. now i really am curious as to how much current is on my coax shield. even though i am not experiencing any rf in the shack, tvi or other undesireable oddities, i'm now certian that my ant. is no where near peak efficiency. it works yes but it could be better, but before i went to that extreme i think it would be on a 5/8 wave design which would have a ground plane. could either of you 2 fc/ marconi recommend a hobbiest priced rf ammeter? thanks guys your'e cuasing me to think again.
i am currently using two models in my balun and antenna tests, both built by mfj, the 853 and the 853H.
thanks free cell i just showed the better half, x mas is coming and " oh my god it's under $100.00) her words not mine so i guess i will probably get it.
any updates on anyones tests of this theory ???
im gona try this balun after looking at all or almost all that i could find avialible comercialy.
www.dxengineering.com/Parts.asp?ID=477&PLID=166&SecID=81&DeptID=9&PartNo=DXE%2DFCC050%2DH05%2DP
im gona try this balun after looking at all or almost all that i could find avialible comercialy.
www.dxengineering.com/Parts.asp?ID=477&PLID=166&SecID=81&DeptID=9&PartNo=DXE%2DFCC050%2DH05%2DP
Marconi said:
imax2000 with gpk1 @ about 40 feet to the feedpoint.
thinking maybe i should isolate the mast fromt the antenna mount somehow. and keep the ground on the mast but decouple it from the anetnna ??? what is your thoughts on that.
I don't like that idea at all, but Freecell is best qualified to discuss this particular idea in detail.
I believe these ideas can produce some improvement for the Imax with a good GPK maybe, but am not sure on the specific details.
I believe these ideas can produce some improvement for the Imax with a good GPK maybe, but am not sure on the specific details.
- No one is chatting at the moment.
