Yes, according to Jay's maunal, T2 adjusts the match, T1 adjusts the radiator length in small increments, and V7 is the tip with the top hat attached, and of course V7 might be said to change the length in larger steps.
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Marconi's I-10K with trombone matcher that works.
- Thread starter Marconi
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Yes, according to Jay's maunal, T2 adjusts the match, T1 adjusts the radiator length in small increments, and V7 is the tip with the top hat attached, and of course V7 might be said to change the length in larger steps.
OK but I don't see a need for that top hat. To me it's just losing 10" of vertical length and adding wind load. If someone is going to run a million watts then a simple ball on top about 2"-3" in diameter would work fine and eliminate the sharp edges of the cross top hat. The Maco, Workman, Gainmaster, Imax, A99 and sigma 5/8 don't have a top hat and they seem to work fine.
Maybe I'll spend some cash and learn to upload you-tube videos and try an I10k at 1/2 wave, 19.5', .625 and .64 just to see what difference the lengths make in performance to different stations at different distances. Now that I think about it, that antenna is made for testing which length works best for certain distances.
I wonder if Jay ever tried and tested it at .64?
NB, in the attached example a Top Hat can be of benefit in raising the current distribution higher up on the radiator, without loss in gain, and maybe a 1* degree increase in maximum angle. Plus of course the issues you make above.
The 1* degree increase may be as a result of this model being only 18' above Earth. If the antennas were higher, this results might not happen.
Theory for the 5/8 wave radiator over the 1/2 wave includes the idea of this increase in the current distribution over a 1/2 wave, so IMO it should hold true in the case of top hats as well. Check out the image below of the side by side Current Reports for wire #3, the radiator. Here we have 20 segments listed for each. The currents are listed upside down in these reports, so the bottom numbers are at the top of the antenna.
Notice from segment #12 up, the maximum current points for both antennas, the antenna with the top hat has the highest currents per segment, and the difference increases nicely all the way up to the tip. More current more higher = more RF higher up.
Again, the arguments are that a full length radiator is always better and in every way, but I say the net differences are probably a toss-up...which is likely undetectable just using our radios.
View attachment NB's Top Hat idea..pdf
IMO, I think some manufactures use these small top hats based on the idea that the larger tip might help discourage lightning better than a small tip. This idea is worth considering also, and for sure if we give up little to nothing.
I don't agree with eznic and maybe I'm wrong but it seems to me the top of the antenna with or without a top hat would see the same lowest current / highest voltage point due to the overall length, and the match & bottom 1/8 wave causing the full in-phase top 1/2 wave of current to fill the top 18' of radiator.
If it moves current up it might be because it's bringing the top lower to where the current isn't yet at the lowest point as if it's just bending the top over sideways.
If you put on a 108" top hat then you would have the highest current at the very top but the antenna would also be 108" shorter.
But that's just something else to test on the I10k at both .625 & .64 with & without the top hat. I hope you're doing your curls and military presses!
It's nice that the I10k has enough extra tubing length to go full length even with the 10" top hat removed.
If it moves current up it might be because it's bringing the top lower to where the current isn't yet at the lowest point as if it's just bending the top over sideways.
If you put on a 108" top hat then you would have the highest current at the very top but the antenna would also be 108" shorter.
But that's just something else to test on the I10k at both .625 & .64 with & without the top hat. I hope you're doing your curls and military presses!
It's nice that the I10k has enough extra tubing length to go full length even with the 10" top hat removed.
I don't agree with eznic and maybe I'm wrong but it seems to me the top of the antenna with or without a top hat would see the same lowest current / highest voltage point due to the overall length, and the match & bottom 1/8 wave causing the full in-phase top 1/2 wave of current to fill the top 18' of radiator.
If it moves current up it might be because it's bringing the top lower to where the current isn't yet at the lowest point as if it's just bending the top over sideways.
If you put on a 108" top hat then you would have the highest current at the very top but the antenna would also be 108" shorter.
But that's just something else to test on the I10k at both .625 & .64 with & without the top hat. I hope you're doing your curls and military presses!
It's nice that the I10k has enough extra tubing length to go full length even with the 10" top hat removed.
NB, I can't tell you that I'm right and that you're wrong on this issue, comparing an antenna with and without a modest top hat, but I have experimented with the idea on an old AstroPlane before.
I couldn't tell any difference operating my radio for a period of time. I just took the top hat off and added a length of 1/2" tubing using two hose clamps. I tuned that length of the A/P until I saw a good match, and in this case the top hat was about 50% of the radiator not 20" inches...like is on the top of this I-10K. That was my only experience doing such a comparison. Even though I couldn't compare side by side, I did look back at my old signal reports at that time and found I was testing this A/P tip idea against my Sigma4 which was the other antenna up. There is not much value in these two reports for the purpose of our discussion, but hopefully it shows I did some work and not just providing words.
View attachment AP vs Sigma4 2009.pdf
Then later when I started modeling I made such a comparison, and noticed similar results with both antennas showing almost identical performance, like I posted above and have posted before. I didn't recall the resulted showing a difference in maximum TOA angle, and favoring the full length 1/4 wave radiator, but I doubt those models were only 18' feet high either, and height might make some difference.
I know these words might not be convincing for you, but this is what I've done trying to figure out...if using a top hat influences performance or not.
I'm surprised you don't even consider the Current Report showing wire #3 for both antennas, showing an obvious increase in the radiating part of the radiator on the top hat model. Remember, the same principal we have here is used to try and explain why a 5/8 wave antenna produces a better signal than a 1/4 or 1/2 wave...by raising the current distribution.
Your argument that the overall currents/voltage should be the same, may or may not be considered descriptive of what is going on here. After all, modeling software uses a controlled input in the NEC engine, maybe 1 amp, so what you say is true to the fact, but you're ignoring the actual current distribution also provided. This same principal is used to describe mobile base loaded vs. center and top loaded antennas. Don't you get it?
NB, I may be wrong in some areas because I think and consider the ideas, but I didn't make this stuff up.
You also comment about the lower portion of the radiator where some of the currents are out of phase, wasted and minimize of any useful radiation in that area of the radiator. That is true. However, you didn't notice, in this important lower area of the antenna we have to consider that the top hat model shows less currents flowing per segment. I consider this like adding current to the top section of the radiator that is really useful in radiating our signal in a positive way.
All this said over an issue for me, that on balance, makes little difference in performance, in theory, and my real world experience. You on the other hand seem to be claiming some notable advantage is to be expected... using a full length radiator instead.
I guess we'll have to agree to disagree.
Have you tested such and idea in some way?
BTW, let me note, that the top hat model is 263.25" tall without including the top hat, and the full length model is 284.25" tall, with the matchs for both showing to be similar. So, the top hat is consider to be a physical 20" top hat, and you add 5% for the electrical length approximately. I just thought maybe you'd like to know that.
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Well, good afternoon my favorite antenna theory sparring partner ^^ ab v c^^
I don't necessarily endorse the .64 as a better antenna than a .625 it just seems to me that having more antenna in the vertical plane, as long as it doesn't cause a rise in the toa, is going to provide more receiving area.
On the 5/8 the top has almost no current as the node is going high in voltage so I don't believe that a top hat or no top hat has much bearing on the transmit performance. proven by the identical transmit performance of the Penetrator w/top hat vs Sigma 5/8 w/o top hat.
Also it seems a capacitance hat on an antenna shorter than a 1/4 wave does more than one on a 5/8.
On the Astroplane the 20" long per side cap hat radials make up for almost 4' of missing vertical element, (more than twice their length) but when I have removed a top hat from a 5/8 all I have to do to bring it back to tuned is add to the vertical element about the same length as one side of the top hat.
And that full model length of 284.25" is what?:blink: That's far too long for even a .64, what is that representing? I know that if you remove the I10k top hat and extend the radiator that same 10" you will have a tuned antenna, but if you extend it to 284.25" it will tune around 26.0mhz(.625)-26.5mhz(.64).
If you decide to sell the I10k please let me know.
I don't necessarily endorse the .64 as a better antenna than a .625 it just seems to me that having more antenna in the vertical plane, as long as it doesn't cause a rise in the toa, is going to provide more receiving area.
On the 5/8 the top has almost no current as the node is going high in voltage so I don't believe that a top hat or no top hat has much bearing on the transmit performance. proven by the identical transmit performance of the Penetrator w/top hat vs Sigma 5/8 w/o top hat.
Also it seems a capacitance hat on an antenna shorter than a 1/4 wave does more than one on a 5/8.
On the Astroplane the 20" long per side cap hat radials make up for almost 4' of missing vertical element, (more than twice their length) but when I have removed a top hat from a 5/8 all I have to do to bring it back to tuned is add to the vertical element about the same length as one side of the top hat.
And that full model length of 284.25" is what?:blink: That's far too long for even a .64, what is that representing? I know that if you remove the I10k top hat and extend the radiator that same 10" you will have a tuned antenna, but if you extend it to 284.25" it will tune around 26.0mhz(.625)-26.5mhz(.64).
If you decide to sell the I10k please let me know.
You could have fooled me NB, but maybe it was someone else that is hung up on the .64 idea...as being something really special.
Also, I guess your words above, concerning the Penetrator vs. Sigma 5/8, sort of proves the point this model tends to show. Again, like I've remarked before, "...I see little to no difference."
The full length of 284.25" is what the extended and re-tuned model ended up being...for the overall length after I made the modification to to the top hat model. This is measured from the physical bottom of the radiator to the tip. The full length radiator is made up of two wires in the model, #2 = 72" and #3 = 212.25", as tuned. The top hat model's overall length is 263.25", with a similar match.
I think you appear incredulous about this length not being a .625 or .64 wavelength for CB, but I've explained already. There are just too many little errors in this model for what you wish to happen. The modification to extend and tune ended up at 21" longer. I started with 20" inches, just like my I-10K manual indicates, but the tune took me to 21" inches. I posted the page regarding the top hat, you must have missed it. The substitution ratio for a top hat appears not to be an exact 1:1 exchange. This ratio turns out to be 5% in this case. Does 5% seem to be some remarkable re-occurring value in antenna work we hear referenced often, like the difference between the physical and electrical lengths of a wire, or the end effect?
This is how my tune turned out, regardless of all the math. Most of those antenna length programs on the Internet don't provide the user the ability to adjust the material resistance, the diameter, or the individual tubing lengths if the radiator is tapered, so you when you get a radiator length you still have to tune.
There probably is math available that will predict pretty close for this issue, and you've probably seen it in books and on the Internet. We see such examples of math, and our eyes glaze over in disbelieve that anybody could understand all that. Modeling is probably as close as you or I are ever likely to get...to using such math.
Also, I guess your words above, concerning the Penetrator vs. Sigma 5/8, sort of proves the point this model tends to show. Again, like I've remarked before, "...I see little to no difference."
The full length of 284.25" is what the extended and re-tuned model ended up being...for the overall length after I made the modification to to the top hat model. This is measured from the physical bottom of the radiator to the tip. The full length radiator is made up of two wires in the model, #2 = 72" and #3 = 212.25", as tuned. The top hat model's overall length is 263.25", with a similar match.
I think you appear incredulous about this length not being a .625 or .64 wavelength for CB, but I've explained already. There are just too many little errors in this model for what you wish to happen. The modification to extend and tune ended up at 21" longer. I started with 20" inches, just like my I-10K manual indicates, but the tune took me to 21" inches. I posted the page regarding the top hat, you must have missed it. The substitution ratio for a top hat appears not to be an exact 1:1 exchange. This ratio turns out to be 5% in this case. Does 5% seem to be some remarkable re-occurring value in antenna work we hear referenced often, like the difference between the physical and electrical lengths of a wire, or the end effect?
This is how my tune turned out, regardless of all the math. Most of those antenna length programs on the Internet don't provide the user the ability to adjust the material resistance, the diameter, or the individual tubing lengths if the radiator is tapered, so you when you get a radiator length you still have to tune.
There probably is math available that will predict pretty close for this issue, and you've probably seen it in books and on the Internet. We see such examples of math, and our eyes glaze over in disbelieve that anybody could understand all that. Modeling is probably as close as you or I are ever likely to get...to using such math.
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I wonder what happened to my post? oh well, maybe I forgot to hit submit. Why not try a top hat-less 276" by 1" diameter radiator with 1/2" diameter radials at 107" and see what gain & pattern you get on 27.205mhz from the model.
I'm a little incredulous toward software but still interested in what the models tell me though I still don't discount the possibility that for some unknown reason a real life scenario might be considerably different.
I'd like to see your graph all filled out with s-units using those measurements to see what the real world outcome would be.
I'm a little incredulous toward software but still interested in what the models tell me though I still don't discount the possibility that for some unknown reason a real life scenario might be considerably different.
I'd like to see your graph all filled out with s-units using those measurements to see what the real world outcome would be.
I also thought you had another post up...that I had not responded too as yet.
Maybe I'll do such a model today.
My models are what they are. I wish I could claim they're accurate examples of what might happen over real Earth, using Eznec's Real Earth feature, or in free space, but I can't do that. They're just something to consider, and that's all, but I don't think they're that far off.
I prefer to compare free space models, but most guys don't appreciate what free space models are suppose to show us or do. Guys get all bent, because they hear stuff saying free space models are theoretical, hypothetical, aren't real, don't exists, and don't represent what we see with real installations or worse yet, complain about how Eznec can't handle Real Earth features. This is why no right minded scientest depends on theory alone, without testing and duplicating real world tests...showing comparitive trend line results.
Before I took up modeling, Bob85 and I use to discuss the issue about free space models. I was tending to agree with Bob's comment, "...my antennas are not in free space." That made perfect sense to me, and it is true, but after gaining some understanding of modeling, and the way and the reasons I think Eznec provides a free space model feature, I've changed my mind on the subject. But, it's just not worth the time or trouble to try and explain.
If I wasn't curious or had questions on the issues you and others raise, then I probably wouldn't even considered suggestions. I just do these models to see what happens, and if I can explain. That said however, sometimes I'm surprised, and sometimes I'm confused, but much of the time it seems the results support what I imagine, and sometimes I have a change of mind.
For me, the big reasons real world results differ from what Real Earth modeling might show us, besides the issues with modeling errors, input, and limitations, is the construction, conditions, losses, and environment within and around our antennas.
The brilliance of modeling is the speed with which the basic math and science, developed years ago, can process the characteristics of these physical wires we call antennas.
In your last sentence, what graph are you talking about, my hand made signal reports?
0h Please do!
Yes, a real world opportunity for the '.6346' to perform and be logged by your careful graphing method.
But if you're inclined toward the upper or lower part of the band it's only fair to reset the length to tune at your test frequency, if & when you try it on your mast.
261" (plus top hat) for 27.385
What is the '.6346'?
What graph are you taking about? Post an image of what you're looking at, if you can't describe it in words or title. My work usually has a title on the top unless you're looking at something hand written.
I don't understand what you are asking me to do, make a model, test a real antenna, or sh*t and go blind? What graph are you talking about?
Sorry, I guess I drank too much of that cough syrup-
In the first paragraph of the pdf you posted a link to of Maxwell he says it's not .64 but actually .6346:
"I have performed a computer analysis
of the 0.64-l' vertieal radiator; a pattern
integration yields 0. 6346 L (228.45" .)
as the true optimum height, furnishing a
gain of 8.1898 dBi, or 3.029 dB over the
?Jfvertical."
I was hoping you would try a model of the 276" x 1" dia radiator(no top hat) with 107" x 1/2" dia radials just to see what the gain and pattern look like.
Then I was wondering if you had interest in putting it up with the top hat at 261" for 27.385 or whatever freq you usually use to test them out to see how it did on your hand-written s-units sheet/ chart as a .64.
I guess I better stop buying *hic* the cherry flavor
Sorry, I guess I drank too much of that cough syrup-
In the first paragraph of the pdf you posted a link to of Maxwell he says it's not .64 but actually .6346:
"I have performed a computer analysis
of the 0.64-l' vertieal radiator; a pattern
integration yields 0. 6346 L (228.45" .)
as the true optimum height, furnishing a
gain of 8.1898 dBi, or 3.029 dB over the
?Jfvertical."
I was hoping you would try a model of the 276" x 1" dia radiator(no top hat) with 107" x 1/2" dia radials just to see what the gain and pattern look like.
Then I was wondering if you had interest in putting it up with the top hat at 261" for 27.385 or whatever freq you usually use to test them out to see how it did on your hand-written s-units sheet/ chart as a .64.
I guess I better stop buying *hic* the cherry flavor
I get it now. I have no excuse for my misunderstanding. I was wondering what you were going to compare this requested model against, and I also assumed you might be asking me to do a real test as well. The model may happen, but the real test won't likely follow.
I do wish I had been able to do my modeling ideas back when I was real world testing. I would have surely done some of what you're suggesting and would not have wasted my time trying to duplicate what other CB'rs might be doing in their installs, it just make sense. I tested at different heights trying to give guys an idea of the significance of height to there antenna, and not so much just to show gain or the advantages of going higher. That turned out to be a total waste of time and effort.
BTW, read the part that Maxwell writes above in italics and quotes, and tell me if you sense his remarks make any distinction...other than the notion about a .64 wave radiator? Maxwell also says,
It is my claim that this whole misunderstanding about the real benefit of the .64 wl radiator has been blown all out of proportions in the CB business, and that this probably happened due to a controversy on this very report by Ballantine in 1923.
You can't just read a few lines of a text, and then claim to understand the full context. NB, at least read the next paragraph and you should get some clue about what Maxwell was really talking about and Ballantine was reporting on. It was not about a vertical CB antenna raised well above the Earth with a ground plane attached.
Also read on down the page and see Maxwell's account of Ballantine's work on why the .64 did not perform has hoped, and what how he described worded his discription of the difference of 1.03 db difference between the .625 / .64 wavelengths.
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i agree with eddie,
it should be noted that these old tests that the 5/8wave bandcampers talk about are ground mounted over an extensive radial system @ low frequencies with the dominant lobe been the lower lobe, not elevated a short distance above ground with 4 x 1/4wave radials @ 11mtrs + mast/feedline and the dominant lobe been the higher angle lobe,
i don't know where the idea for the equivalent length of a hat came from but there is more to it than adding the length of one hat spoke to the element,
if you remove the hat from a i-10k and retune you will end up over .6346wave as eddie claims,
something else to think about,
Method of Moment Proofs
"The moment method proof, however, is not applicable in all cases or array designs. For instance, arrays utilizing top-loading, sectionalized elements, or folded unipoles (i.e. skirted towers) must go the traditional route. In addition, shunt-fed elements also preclude the use of the method of moments. Therefore, the use of this process is more or less limited to the run of the mill "traditional" designs."
from wiki
NEC versions
There are at least four versions of NEC, with NEC-2 emerging in 1981 and NEC-4 appearing in 1992. NEC-2 is the highest version of the code within the public domain without license. NEC-4 remains proprietary with the Lawrence Livermore National Laboratory and the University of California.
NEC-4 currently requires a separate license for use. The licensing details are available from Lawrence Livermore National Laboratory here.
MININEC was a version first written in BASIC for home computers. It first emerged in 1982 on the Apple II computer. MININEC computational engines are now written in FORTRAN to improve speed. MININEC is an independent implementation of the method of moments. The basic algorithms are based upon the advice of Professor Wilton at the University of Mississippi (now with the University of Houston).
MININEC suffers from some known flaws compared to NEC, the best known being that resonant frequencies may be slightly in error. However, MININEC handles different wire diameters better than NEC2 and probably NEC4[1]; this includes different diameter parallel wires, different diameter wires joined at an angle, and tapered diameter antenna elements. Placing sources at an intersection of two wires is a problem for NEC2 but not MININEC[2]. MININEC converges more slowly (requires more segments) when wires join at an angle, when wire segments of significantly different length are adjacent, and has a weaker ground model[3].
[edit] NEC in the field
Although antennas can be simple structures, the modeling of these systems does require a certain level of understanding of the electrical characteristics of antennas.
As a starter for any modeler, 4nec2 or EZnec can be used. See their respective home pages for further information on their purchase and/or installation.
[edit] Limitations
Does EZNEC v. 5.0 use NEC-4 for calculations?
Of the five EZNEC v. 5.0 program types (demo, standard EZNEC, EZNEC+, EZNEC Pro/2, and EZNEC Pro/4) only EZNEC Pro/4 uses NEC-4. NEC-2 is the calculating engine used by the other EZNEC programs. See the next item, below, for more information.
There are two professional (EZNEC Pro) programs, EZNEC Pro/2 and EZNEC Pro/4. They are identical except that EZNEC Pro/4 can use NEC-4 for calculations as well as the NEC-2 used by the other EZNEC program types.
The primary advantages of NEC-4 are that buried conductors can be modeled, and NEC-4 is relatively free of the small error produced by NEC-2 when analyzing connected wires of different diameters.
it should be noted that these old tests that the 5/8wave bandcampers talk about are ground mounted over an extensive radial system @ low frequencies with the dominant lobe been the lower lobe, not elevated a short distance above ground with 4 x 1/4wave radials @ 11mtrs + mast/feedline and the dominant lobe been the higher angle lobe,
i don't know where the idea for the equivalent length of a hat came from but there is more to it than adding the length of one hat spoke to the element,
if you remove the hat from a i-10k and retune you will end up over .6346wave as eddie claims,
something else to think about,
Method of Moment Proofs
"The moment method proof, however, is not applicable in all cases or array designs. For instance, arrays utilizing top-loading, sectionalized elements, or folded unipoles (i.e. skirted towers) must go the traditional route. In addition, shunt-fed elements also preclude the use of the method of moments. Therefore, the use of this process is more or less limited to the run of the mill "traditional" designs."
from wiki
NEC versions
There are at least four versions of NEC, with NEC-2 emerging in 1981 and NEC-4 appearing in 1992. NEC-2 is the highest version of the code within the public domain without license. NEC-4 remains proprietary with the Lawrence Livermore National Laboratory and the University of California.
NEC-4 currently requires a separate license for use. The licensing details are available from Lawrence Livermore National Laboratory here.
MININEC was a version first written in BASIC for home computers. It first emerged in 1982 on the Apple II computer. MININEC computational engines are now written in FORTRAN to improve speed. MININEC is an independent implementation of the method of moments. The basic algorithms are based upon the advice of Professor Wilton at the University of Mississippi (now with the University of Houston).
MININEC suffers from some known flaws compared to NEC, the best known being that resonant frequencies may be slightly in error. However, MININEC handles different wire diameters better than NEC2 and probably NEC4[1]; this includes different diameter parallel wires, different diameter wires joined at an angle, and tapered diameter antenna elements. Placing sources at an intersection of two wires is a problem for NEC2 but not MININEC[2]. MININEC converges more slowly (requires more segments) when wires join at an angle, when wire segments of significantly different length are adjacent, and has a weaker ground model[3].
[edit] NEC in the field
Although antennas can be simple structures, the modeling of these systems does require a certain level of understanding of the electrical characteristics of antennas.
As a starter for any modeler, 4nec2 or EZnec can be used. See their respective home pages for further information on their purchase and/or installation.
[edit] Limitations
- NEC-2 does not model tapered elements such as those made of telescoping aluminum.
- NEC-2 does not model buried radials or ground stakes.
Does EZNEC v. 5.0 use NEC-4 for calculations?
Of the five EZNEC v. 5.0 program types (demo, standard EZNEC, EZNEC+, EZNEC Pro/2, and EZNEC Pro/4) only EZNEC Pro/4 uses NEC-4. NEC-2 is the calculating engine used by the other EZNEC programs. See the next item, below, for more information.
There are two professional (EZNEC Pro) programs, EZNEC Pro/2 and EZNEC Pro/4. They are identical except that EZNEC Pro/4 can use NEC-4 for calculations as well as the NEC-2 used by the other EZNEC program types.
The primary advantages of NEC-4 are that buried conductors can be modeled, and NEC-4 is relatively free of the small error produced by NEC-2 when analyzing connected wires of different diameters.
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I got out of that page that when he went to the shortened .528 version he lost 1.03db but eliminated the cancellation at 35 degrees.
And the 5/8 thing, well .625 is real close to .6346 so I can see why they would give it the nickname of a 5/8. I just wonder if there is much of a difference at greater distances using the .6346 versus a .625 aside from the models, in the real world.
Maybe I can build a home made version of it so I can test different lengths.
Still it seems kind of like a moot point now with the Sirio Gainmaster on the market.