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[TowerTalk] More Interference Pattern

To: "towertalk@contesting.com" <towertalk@contesting.com>
Subject: [TowerTalk] More Interference Pattern
From: David Gilbert via TowerTalk <towertalk@contesting.com>
Reply-to: David Gilbert <ab7echo@gmail.com>
Date: Tue, 14 Apr 2026 13:30:22 -0700
List-post: <mailto:towertalk@contesting.com>

I decided that the SVG version of the moving interference pattern I previously linked had some flaws.  The motion was at a constant rate and the direction of the motion of the combined diffraction pattern should have been in any direction.  Codex had difficulty resolving those problems within SVG so after many iterations I told it to switch to a Canvas implementation within JavaScript/HTML.  I think the result is much more accurate and is located here:

http://www.ab7e.com/Interference Pattern.html

Notice that the red and green arrival angle lines now shift in phase relative to each other in sync with the displayed phase shift ... which also now goes both positive and negative.

The interference pattern of the combined waves is now the much broader shaded light colored pattern and it now shifts in multiple directions.  The is a more accurate display compared to the SVG version ... which turned out to be more illustration than representation.

A really key point is the comment made by Gemini (another AI agent) that my good friend Bob, K7ZB used to analyze what is going on.  And that is:

What we really measure when we compare the phase of the signals from two antennas is the instantaneous GRADIENT of the interference pattern that results from multiple signal paths (both relative angle and relative phase) due to propagation and various local reflections (ground, nearby terrain, other structures).

Not sure if anyone else finds this stuff as interesting as I do, but at least it explains what I empirically found when trying to use my ArrivalAngle application.

73,
Dave   AB7E


p.s.  For reference:

(http://ww.ab7e.com/ArrivalAngle.html).
(https://youtu.be/MxRaYSRMPE4)








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