Possible ADS-B Reflection by Mt. Fuji β Part 4 π»
Possible ADS-B Reflection by Mt. Fuji
As shown in Parts 1β3, faint UHF ADS-B signals occasionally appeared from the unusual western direction.
Whether this is caused by reflection from Mount Fuji or by diffraction over surrounding mountain ridges remains unclear at this stage.
This blog began with a simple observation.
While listening to a conversation between amateur radio operators, I heard a comment that stayed in my mind:
βIf you point your antenna toward that local mountain, reflected signals travel surprisingly well.β
That small remark became the starting point of this experiment.
Then something even more puzzling occurred.
Abnormal signal propagation?
March 14, 2026.
While reviewing my receiver statistics, I noticed that ADS-B signals had appeared from a direction where reception should have been impossible.
Given the installation height and directional characteristics of my antenna, signals from the north-east (NE) and east(E) sector should normally be blocked by terrain and building.
However, the statistics showed reception at a distance of 232 nautical miles (about 430 km).
The dataset contained 124 hits beyond 150 nm, corresponding to that direction.
Based on the distance and geometry, the aircraft was likely flying along an international route over the Pacific Ocean off the coast of Miyagi Prefecture.
At first glance this seems like an ordinary long-distance reception.
But when the surrounding terrain and antenna orientation are considered, the geometry becomes difficult to ignore.
Signals appear in a direction that should be shadowed, almost opposite to Mount Fuji.
Whether this is related to reflection from Mount Fuji or diffraction across mountain ridges remains an open question.
Future experiments will attempt to verify this possibility.
For now, however, let us return to the original storyβ the replacement of the USB SDR dongle.
This blog series ends here.
What started as a small curiosity about ADS-B reception slowly turned into an exploration of radio propagation, mountains, and geometry.
Future updates, tools, and data will be shared on GitHub.
Project repository: https://github.com/catgpt-glitch/
https://catgpt-glitch.github.io/
Until the next signal appears somewhere unexpectedποΈ