Well Bob, I guessed wrong again on what you meant regarding the physical distance between the two elements. I was sure you meant the top of the radials elements in the 1/4 wave cage were curved back to the radiator and thus too close...the opposite of what we find in the cage for the Vector/Sigma4.
The Big Mac looks to be raised 4"-6" under the coil and for me that is plenty of space, so how much space would you think is enough in such a case? I would question this idea of reversing currents in a collinear in the Sigma4 before I would question it in the Big Mac just because there is an insulated space between the lower and upper elements. That said in either case, neither the Big Mac or the Vector/Sigma4 would work worth a hoot if this current reversing function did not take place at the top of the bottom 1/4 wave element. Else both antennas would show the results of an end fed 3/4 wave monopole or longer, and I don't believe either of us believes such an antenna will work very well to put RF on the horizon.
I think you're right again Bob, but when you suggested I read-up again on "Ia" & "It", I had the feeling of deja-vue all over again. I can't remember the details back then, but I probably had similar questions, right? At the very least I questioned your considering the 31' foot length you used and found around that length to be optimal for performance at a far distance. And you're also right, tapper and larger diameter will make both radiators appear longer, and for me that makes my question even more of an issue, not less.
Tell me if my thinking basically describes the significance of these two different currents. The transmission line mode "It", suggest currents that do not radiate due to cancellation like coax, whereas antenna mode currents "Ia" do radiate, like common mode currents, another current in the mix?
I guess I'm wrong again then, because if you're suggesting here is that there are transmission line mode currents in the bottom, and I'm right in my idea noted above, then there would be no RF coming from the bottom 1/4 wave due to cancellation. See how this subject flips one way then the other, while still evading my understanding. Seems like every time I get an idea about this subject...I always run into a conflict to that thinking, kind of like a road block or maybe a metal block.
I can't prove it Bob, but I tend to think the only reason that Sirio extended the length of the radials to 106" was to maintain 1/4 wave resonance to a workable radiator length ratio that worked about the same as the earlier model, with the main goal being to try and shorten, for durability sake, the length of their Vector antenna. You have often talked about this problem in your area, and I'm sure after looking at several Vectors here, they do not hold up well...even in milder climate areas. I have yet to see or hear any real reports on the New Vector 4000, other that they're alright and work pretty good, but based on my experience recently with two other Sirio antennas, I tend to believe that Sirio knows what they're talking about.
I agree, that is what the book says, but my point in raising the issue was to note that in order to get to this 4:1 point with this ratio idea in the ARRL, the antenna would have to be about 36' feet long and then you might see a very narrow spot close around such ratios listed, and little room for error or there would be little to no antenna currents to radiate. So see, here is my dilemma noted again, if my bold typed idea above is not right, tapered tubing and larger diameters or not. I know such factors need to be considered in antenna design, but I just can't get this current idea you raise...good in my mind's eye.
