Because most of the CMC has already been radiated off the resonant 1/4 wave cone, very little happens if we take the time to insulate the base and add the coax choke. I've been able to measure virtually no change in impedance and the slightest drop in gain when doing this. That is due to the fact that any remaining CMC on the mast and coax would be in a constructive phase closest to the feedpoint connector.
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Question on the Vector
- Thread starter The DB
- Start date
Because most of the CMC has already been radiated off the resonant 1/4 wave cone, very little happens if we take the time to insulate the base and add the coax choke. I've been able to measure virtually no change in impedance and the slightest drop in gain when doing this. That is due to the fact that any remaining CMC on the mast and coax would be in a constructive phase closest to the feedpoint connector.
i stated from day 1 over 10 years ago that the 4 radial vector shortend outperforms the 3 radial avanti and the old style vector eddie, not that i don't see anything with the avanti,
i have said a dozen or more times what the problem is with your testing,
im not saying my way is perfect far from it but we eliminate as best we can 4 variables you include in your tests,
eddie,
how does your one set of currents jive with this ?
in the open sleeve antenna as you bring the sleeve element spacing closer to the monopole the input impedance of the antenna drops and current increases,
what causes that eddie?
it is claimed that sleeve spacing has little effect on Za ( monopole antenna mode impedance ) so we can't blame the sleeve for causing a drop in Za as been the cause of the lower impedance and increased current,
you have not changed the physical length of the monopole or radials to change Za,
it is claimed that Za may even rise a little as sleeve spacing decreases
why do we see impedance drop and current increase eddie ?
i have said a dozen or more times what the problem is with your testing,
im not saying my way is perfect far from it but we eliminate as best we can 4 variables you include in your tests,
eddie,
how does your one set of currents jive with this ?
in the open sleeve antenna as you bring the sleeve element spacing closer to the monopole the input impedance of the antenna drops and current increases,
what causes that eddie?
it is claimed that sleeve spacing has little effect on Za ( monopole antenna mode impedance ) so we can't blame the sleeve for causing a drop in Za as been the cause of the lower impedance and increased current,
you have not changed the physical length of the monopole or radials to change Za,
it is claimed that Za may even rise a little as sleeve spacing decreases
why do we see impedance drop and current increase eddie ?
I agree Bob, you have told us this for a long time.
However, my models do not support that idea if I compare my S4 model to my New Vector 4K model. At best however, the difference was not much, and what this looks like to me using the models as a reference...is the difference was so small I don't think anyone could determine a notable difference just using a radio. I also see video of other's comparing signals an often they are talking needles width differences.
Do you really think, because I see something different here...that I'm calling you a liar?
I know modeling is not perfect, but neither is looking in the air at your antenna work, listening to your radio, and/or recording signals, propagation being what it is.
In all my experience fooling with my real antennas I have seen occasions when one antenna seemed better than another, but when I compared them, signal for signal over some period of time with some of my regular contacts, and then later compiled this data into a recap...I just didn't see anything near an S-unit of difference like many claim. But I don't consider them as liars.
I know there are issues with the testing I have done, but I did what I could and I was surprised to find that all my antenna performed about the same when I tried to get the current maximums at or near the same height. Maybe this lack of difference I see is because most mount their antennas all on the same height mast, regardless of where the current max is.
Regarding my modeling, I think I've added extra length to both S4/NV4K models that you and Donald have reported to have added to your antennas before. I don't remember specifically what effect this had, but maybe I'll check that out and report back.
Bob, this is bull crap. I could complain about your testing too, but I don't. I figure you did what you thought best, and reported what you saw.
Toward the end of my testing days I went to a lot of extra trouble to mount most of my antennas on the same mount with everything in the setup the same. I recorded the same guys signals I always did, sometimes for a day or two and sometimes for a week to a month. I recapped those reports too, and surprisingly these guys signals were very consistent with the testing reports I got earlier...and this was with two antennas mounted 36' feet apart on an antenna switch.
Every where you look in the world of communications antennas you see installations of multiple antennas mount much closer together than mine.
Donald makes similar claims, but on his Website he shows his Dominator mounted with a score of other antennas right there in the same area.
Maybe I'll post on the rest latter, I'll have to restudy the rest.
Bob, could I ask you if a 3/4 wave monopole model with 4 radials and no hoop on the top work for you in the rest of my response to the ARRL ideas if I decide to add a model to help explain what I see? The hoop on top of the radials is a lot to deal with making changes to the model easily.
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no need to mess with hoops eddie,
a 3/4wave mono-pole fed at the base with two or more 1/4wave sleeve elements spaced a couple of feet from the monopole and another spaced about 6-8" from the monopole should do it,
the antenna is ground mounted.
a 3/4wave mono-pole fed at the base with two or more 1/4wave sleeve elements spaced a couple of feet from the monopole and another spaced about 6-8" from the monopole should do it,
the antenna is ground mounted.
Lets be clear on this one Marconi. While some clients are forced to share tower space in close proximity to other antennas, I would not be attempting to run gain tests or confirm the pattern while other antennas are present and could interfere with the results. All of my tests were conducted with no other antennas around for many wavelengths and done in the FM mode. The Sigma design produces the exact same signal as a 1/2 wave dipole when the Sigma has a 2db attenuator inline with it. Not measured in needle widths on a signal meter but with the accuracy of digital instruments.
eddie,
please show me a test you did on the same pole within a couple of minutes, with willing participants who are ensuring steady transmitter output using unmodulated carriers and no skip or multipath flutter screwing your test up,
thanks.
please show me a test you did on the same pole within a couple of minutes, with willing participants who are ensuring steady transmitter output using unmodulated carriers and no skip or multipath flutter screwing your test up,
thanks.
I was never able to work fast enough doing my testing on a single pole to do such a test Bob. The only way I could compare signals on these antennas that quickly I had to use a antenna switch box and have two antennas up at the same time.
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I know Donald, I have to share my space for antennas with stuff on the ground and above it too...that is too close as well. If I was able and going to do real testing of my antennas I would do it differently too, but no matter what I did...I'm sure someone would question the results. And that is alright by me, because sometimes I learn something I didn't know in the process of considering the experiences of others.
I wasn't intending to complain about your install, I was just trying to show something to Bob about how the real world out there really is.
I wasn't intending to complain about your install, I was just trying to show something to Bob about how the real world out there really is.
Bob, are we discussing the Open Sleeve antenna or the Skeleton Sleeve antenna? For some reason I think we were talking about the Open Sleeve antenna earlier, but after some checking I see where I might have misunderstood you when you mentioned such an antenna. My model of the Open Sleeve is a model that came with Eznec software. I did no make it.
I've been looking for my model of the Open Sleeve antenna and it is just a horizontal dipole with a 1/4 wave sleeve over the center portion, similar to a regular dipole.
I've already asked if this is the Skeleton Sleeve antanna rather than the Open Sleeve, but to be sure I did not know it was ground mounted. The picture in the article does not look like it is ground mounted.
At any rate, Eznec does not claim to work well if mounted on the ground.
http://www.worldwidedx.com/threads/the-skeleton-sleeve-fed-monopole.151071/
Bob, here is a link to a post I made that talks about my model of the SSFM article.
Bob, here is a link to a post I made that talks about my model of the SSFM article.
Bob, sorry about that, I wasn't prepared to answer right then. Here is the question you asked me in the older thread that I posted over a year ago about "The Skeleton Sleeve Antenna" model I made.
First off this antenna in the "Open Sleeve Antenna" article is not similar to the S4/NV4K designs. It is a 1/2 wave radiator in the middle of some 1/4 wave elements noted to be a sleeve. I'm not sure about the relevance to a monopole antenna that is as long as 3/4 wave, but the ideas presented could apply to either length monopole, so I will respond further.
The simple answer to your question is noted right at the start of the article...the closer the spacing the lower the impedance and the higher the frequency of the monopole. This is exactly what I find using the Eznec idea I asked you about with out the cone attached. However, I see there is not much drop in impedance unless you possibly start the model with the sleeve elements a 1/4 wavelength away from the base of the monopole...like I read the description for this ground mounted antenna in the Open Sleeve Antenna article.
The wires in my model are all the same size, and are far closer together like the S4/NV4K, and the model in the "Skeleton Sleeve Fed Monopole." Bob, have you noted that this title suggest that the sleeve is feeding the monopole? Words have meaning.
To be fair, I also note in the other article, "The Open Sleeve Antenna," suggests the following:
The article "does" also claim the results reported are determined by the characteristic impedance, end impedance, the length of the 3-wire transmission line formed by the central monopole and the two sleeve elements, and the D/d ratio.
I remember you asking this question below in another post above, and saying the following. I highlight the words below in your post that I question...where you may have misspoken. If true Bob, this is not a problem, because I think I understand your point.
So that I'm not confused which is right, currents increasing or higher frequency?
You know Bob, I agree with the description in the comments from the Open Sleeve article noted above. The difference is how I see what is said...compared to what you see is said.
What if the Za and Zt business only has to do with how this antenna might be tuned if we use a 3/4 wave monopole rather than a 1/2 wave radiator, and/or a reduction in the spacing distance from the base of the monopole. Do you remember that Homer and Booty Monster both talked about problems with tuning their Vectors, and I told them both that the hub distance the radials were from the base of their radiator was important to get right?
Transmisson lines theory says coax line does not radiate...except when specific conditions exist at the load end that are not resistive. I see the cone showing transmission line currents also, just like the article suggests. There are two currents that are very nearly equal magnitude and opposite current phase, thus we have no radiation into the far field just like coax works and this is due to cancellation.
You see the issue as though there are CMC's flowing on the outside of the radials, but that would only happen if there was a significant difference between the combined currents on the radials vs. the currents on the out of phase monopole, and I don't believe the cone is coaxial. This is not what my Eznec models show either, and I don't believe CST is showing that either. Again if you check the current inside the top of the cone you will see there is a bit of difference in the red and blue currents.
My models shows these out of phase currents inside of the cone are about equal in magnitude, and the very small difference is all that will possibly radiate due to cancellation, and that radiation could be either constructive or destructive...depending on antenna construction.
BTW, the 3/4 wave wave monopole I modeled with slanted up radials like the NV4K, but without the hoop attached, shows what I am suggesting here. You and Donald cannot show any evidence that the currents on the outside of the Vector cone are CMC. The pattern looks wrong for a 1/4 wave radiating element too.
I say it again, due to transmission line currents inside the cone...we have cancellation and thus little to no RF into the far field. Thus the cone helps block most of the detrimental out of phase current in the cone area and does not ill-effect the tune of the antenna much and the bad effects that cause a 3/4 wave radiator to make a high maximum angle of radiation.
Donald might could prove this one way or another if he could produce some real details for the CST currents data. I don't know anybody else that has a connection with Sirio in such matters like he does.