Home: https://ky8d.net/spiral
Series:
[1]
[2]
[3]
[4]
[5]
Why? Keeping the last round's chosen value for the spiral expansion factor (CLI arg '--tau 3.7'), here I proceed to iterate over a range of possible spoke counts (aka 'radii count', CLI arg '--div'). Thus will all spirals below exhibit the same degree of general tightness, but vary as to the aliasing of their curve resolution. Viewing the plots will inform me of how few I'll be able to get away with in simulating a spiral.
Color Key for Paragraph Text: White (greater contrast) presents information crucial to interpretation. Red presents a delving into various fiddly details about the surounding main text in white. Stuff which I feel some readers may find self-evident, uninteresting, or even beside-the-point. Tidbits I couldn't convince myself to simply delete.
Anomaly: Regarding the sharp upwards step present in the F/R and F/B traces at 22.034 MHz within the plot at top left of a 6-divison spiral, I discovered as follows. Firstly, no amount of zooming in to higher resolutions (even as small as 1kHz) provided a smoother transition. The step remained. A check of AGT at 22.034 MHz returned a perfect 1.00. Plotting the currents for 22.034 MHz, however, I discover a bend in the wire of 60° almost exactly bisecting a pair of mirrored high-current regions. See diagram below.
For clarity's sake, the current-plot above derives from a Nec2Go screenshot imported into Inkscape as a PNG, where I traced over curves manually, then deleted the PNG, saving as SVG.
Insofar as I have a particular interest in the WARC bands (refuge of sanity during contests), and 12m is still poorly served, even with 16 divisions, I must consider what is the issue. Could it be that portion of the spiral antenna's relation to ground? Maybe if I try out different attitueds of spiral 'spin', maybe I can balance that out.
And so, that's what I'll try next: Iterations on Spin.