Donald are you saying that the J-Pole does not have a reputation for having CMC problems? W8JI was suggesting CMC problems with the J-Pole/Vector in Booty Monster's thread on eHam too.
Of course not. I built my first J-pole decades ago and found it was a decent coax radiator. I'm aware of CMC with the J-pole. The better question is do you think the end fed Sigma wouldn't have CMC had these currents not been radiated from the cone? When W4OP and W8JI can fit a 1/2 wave current shape over a 1/4 wave radiator into their explanations, we can begin to consider them and why the 90 degree collinear experiment works.
Try reading what Cebik writes at the bottom of page 3, in one of Bob's regular references, "Some J-Poles That I Have Known." This page is posted below, but I doubt you will bother to read it, because it shows you have your head in the sand.
Nothing shows one's head in the sand like their denial to accept what works in the real world in favor of a flawed model year after year after year. No reason to read about J-Poles. Nothing there can explain the 90 degree phase shift taking place in the "non apparent collinear " antenna.
The only problem with the J-Pole IMO is a result of its being out of balance at the feed point a bit, no matter what you do. I use to believe much of this crap about our vertical CB antennas being out of balance, and thus CMC's being a hugh problem that basically rendered our antennas usless...but I now say horse hockey in most cases. CMC's may be a much bigger problem with ham multiband antennas, but not the commercial CB antennas we have available...including most of the EF Solarcon antennas.
I think CMC's currents can produce problems if their magnitude is worst case, but if these currents are minimal and within reason...this idea is mostly BS we hear about the operations of our CB radios. The only thing I see being a problem is interfering with other nearby electronics. If you eliminated all CMC's in your antenna I suspect you could see no operational differences in performance with our commercial line of CB antennas. This dose not mean there are not differences that can be measured using high tech devices...it means you are not likely to see differences using your radio because the differences are so subtle.
I've also seen a few installations where an Antron 99 had little RFI problems and was able to work surprising skywave propagation. Just a few blocks away someone with the same antenna is never heard in DX and has a good deal of RFI problems. These same situations have been noted in many installations. The difference is mast and coax length used and the phase of the CMC that freely radiated without choke or resonant path to bleed the currents off.
Do not underestimate the damage CMC can do to an antennas pattern if the CMC is not effectively addressed at the antenna. When the CMC is allowed to radiate in a destructive phase, it causes high angle lobes to take power away from the horizon as well as causing RFI.
I don't understand this at all.
It's simple. W8JI expects there to be significant CMC still present on the coax. He also anticipates this CMC will be radiating in a deconstructive phase in order for the "pattern to fall apart once the coax and mast are added". I added them and the gain dropped a few tenths of a db with virtually no change in the perfect match. I bent them up and the missing gain returned.
Some of the productive CMC current on the cone is forced to divide between the cone and the horizontal radials. The diverted currents on the new radials is essentially wasted since it's in the horizontal plane. Leave the end fed CMC currents exactly where Herb placed them. On the resonant cone where they benefit gain while reducing RFI.
I've posted about this here on WWDX, but nobody responed or else, like you suggest, nobody noticed or understood what I was describing. I also posted this idea on eham, and one other member that I remember agreed with me.
One member agreed with you on what point? That the shape of the 1/4 wave pattern was odd? Was any other point made or conclusion drawn? Pointing something out falls short of explaining what we see in a manner that fits sound RF theory and the results which can be repeated in the field.
I agree with the first part of your observation, but I do not think it possible to phase shift a 1/4 wave element like I think you are trying to suggest. Maybe this is what DB was asking about in his short post above.
Donald IMO this is another anomoly that I think you see, and are trying by some words or silly idea to justify. The Sigma 4 antenna is a very good antenna for a lot of reasons, but there is nothing magic about it.
Why am I not surprised? How about this, I agree, you can't see the phase shift I'm talking about. Now can we please move onto why this is the case and stop accepting data from a model that will not produce a model that resembles the 90 degree phase offset we can clearly see in the field?
You don't see this offset in phase using EZNEC because it has only been able to accurately predict one of the two currents required to place a 1/2 wave shaped current on a 1/4 wavelength radiator. When you only see one current correctly, it is not possible to form a current like this. You only get the maximum current at the base like your EZNEC models continue to misrepresent.
Your humble opinion once again borders being insulting as I watch you use it as an excuse to stand behind your idea in favor of what works. I'd like to hear your "idea" about how that pattern is formed at the 1/4 wave base of the Sigma??? If you can make it fit what works in the field along with what we see in CST like I did, that would be the icing on the cake.
You're just guessing here, but that is alright with me.
Guessing is what one does when they do not have the ability or time to test their own ideas for themselves and has to endlessly wait for others they consider unbiased to test the idea for them. In the meantime, they are forced with no other option but to guess. Sound familiar?
This is vastly different from someone who suspected the typical models have misidentified a 1/4 wavelength of radiation current and then comes up with a way to prove the 90 degree phase discrepancy with the collinear field tests. Who is really guessing Marconi?
