CDX-007,
Well, I was right in what I said, but since I was 'looking' at the wrong coil (didn't actually look, "assumed" I knew which one I/we were talking about) what I said was wrong. In the pictures, the coil inside of the base tube does go to ground. It, along with the 'loop' attached to the vertical radiating element forms an inductive impedance matching circuit for the 5/8 wave antenna.
In one of the earlier posts, 'M.C.' said that because of the added coil, the length of the antenna had to be changed to 'make up' for the inductance of the added coil. And that is the reason for the difference in antenna length.
But, it doesn't have to be done that way if you are willing to adjust the respective sizes of the small added coil and the 'loop' till you have the correct relationship between the two. Being practical, that's a lot harder to do than just adjusting the vertical element's length (and that's what most manufacturors are after, quick and easy changes... otherwise it just costs too much, right?).
The over all affect is the same, sort of, speaking of 'resonance', of the whole antenna, not just the length of the vertical element. The difference in length just isn't all that much so the difference in performance (because of that length change) just isn't that much either. Some, but not much, and certainly not enough to be readily noticable due only to the length change.
- 'Doc
PS - If I'd pay more attention I wouldn't make 'assinine' mistakes, huh?
