Is this author correct about using a λ/2 of wire for a coil to get the proper delay on a λ/2 collinear antenna?

Improving the Super-J August 5, 2012 by John S. Huggins

I agree with him that there has to be a 180 degree current delay between λ/2 collinear elements, but if winding the phasing wire into an inductor (Figure 1D in his article) of a certain minimum value, couldn't that produce 90 degrees of current delay anyway, necessitating only λ/4 of electrical length to get to the other 90 degrees of current delay?
I agree that λ/2 of wire is needed if the design uses a hairpin stub, but if you're going to make a coil, I would have thought that would have produced some calculatable current delay anyway.

Secondly, does anyone else think that the separation he proposes as best (~16" on the 2M band) between λ/2 radiators, is actually not correct? Intuitively I would have thought that keeping them as close together as possible would actually be preferred to achieve a flatter main lobe and less prominent ancillary lobes?

Thirdly, I would think that if the coil he makes doesn't have sufficiently high impedance, it will be as if both elements are too long, or worse, that they are acting as one element.

  • $\begingroup$ He seems to acknowledge your separation point in his article, especially around figure 3. He's micro-optimizing gain at the expense of side lobes. The "curved stub" in that graph, to your point, seems to show what you and I agree is "best" but he is clearly aiming at a different "best" target. $\endgroup$
    – webmarc
    Jul 26, 2021 at 11:22
  • 1
    $\begingroup$ I find his coil impossibly low in inductive reactance. When I run the calculation, his coil appears to be 0.404uH and 370 ohms at 145Mhz, which seems like it would be way too low. He also has no VSWR data on the actual antenna as built. $\endgroup$ Jul 26, 2021 at 16:19


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