Do you mean there is a difference in phase between one side of the vertical and the other? I understand phase as changing along the length of the radiator and not from one side to the other.
I must confess I don't totally understand how CMC affects the vertical element. I thought these currents flowed on the outside of transmission lines and not on the vertical radiator itself. I evidence in the CST model and from the engineer who built the model that CMC are in phase on the cone and transmission line. Since the cone is only 1/4 wavelength, most of the currents radiate there. That same phase continues along the first portion of the mast and coax. I'm not sure if I misspoke or made a mistake before but I'm not sure where the inconsistency is here.
The builder of the CST model explained that the small amount of current descending on the mast (or coax) would add another small benefit to the antennas gain. How does the phase shift taking place inside the cone complicate the any CMC current since it appears to be in the constructive phase. It appears the CMC current would start at the top of the cone since it has to fold over the outside of the "transmission line".
It looks like the path would be through the 1/4 wave radials and any residual CMC on the mast should follow this same constructive phase over the first 1/4 wavelength of mast and coax. That is a much better condition than having the first section of mast or coax bucking the phase of the antenna. Again, it seems the only thing responsible for making this change in phase is the fact the vertical has been phase delayed by 90 degrees. I see no change in phase of the radials in the cone or CMC currents, only in the main radiators phase.
I agree with your assessment based on the video CST produced. I was expecting to be able to find frames in the video that would show the inside surface of the cone to have the same phase as the outside, at least right up on these elements. It is not apparent there but I will elaborate more on this idea below.
That is what you we happening inside the cone. The phase change takes place starting right at the feedpoint and continues through the inside of the cone.
You may be onto something now. I've been assuming the source of the CMC had to be the top of the cone. Where this current begins is very important to determine its phase with respect to the rest of the antenna. Let's go one step further and forget about CMC and just look at the normal radials currents with this same thought in mind.
Suppose the electrical length of the cone is not just 1/4 wave and the currents have to travel up the inside surface and down the outside surface? There is another 90 degree offset in phase occurring here in that case. Is this offset in the right direction to correct the collinear problem? Another thought I had was could the 3/4 wavelength radiator have an affect on the phase of any currents going on at the base cone like it changes the phase at the base of the main vertical?
Now we are in the gray area a little because I can't see opposing currents inside the cone but at the same time this would have to be the case if part of the function is to act as a transmission line to the 1/2 wave. I can't be sure if that is due to the opposing fields having "pushed" the radiating currents to the outside as it would if the principles were simply magnetic or if the currents are truly that different on the two sides of the cone.
The engineer did comment that any currents descending on the first part of the mast would add a small gain as mentioned before. Currents on the mast would have to be CMC. Do you not agree? The only reason we don't have the J-pole CMC issues in this design is the cone. It's fairly logical to assume it must have a majority of those characteristic end fed currents radiated from the cone.
If you make enough error in the resonant length of the cone you'll get RF burns on your lip from your mic. Not to mention every change in coax length or movement of the cable can begin to affect the SWR. Properly tuned and drastic changes here make just about no change in the most sensitive measuring equipment. Going to the extent of removing the meter movement from the directional coupler and replacing it with a millivolt DVM.
As I recall Bob has also indicated CMC are responsible for some of the cones radiation. I think I'm guilty of putting too much emphisis on the CMC current as there is more than one current on the cone.
