Having analyzed the environment in a bunker and a chalk mine with the same concept, I decided to test the idea behind the experimental design further.
I placed a watch with a BT signal in an aluminum cylinder (diameter 10 cm, length app. 1 m) welded closed at one end and open at the other. The HackRF Antenna was placed horizontally into the cylinder pivot mounted outside the cylinder with a folded aluminum insulation sheet below, around, and above the experimental setup containing the antenna. A 3min test run with and without the BT watch was run without any further precautions inside a house with several wireless devices including PC notebook, wifi router, mobile phones, and other BT devices.
There is a clear detection of the signal at 2406 MHz, as seen from the contrast plot.
From the cumulative summation plot, we observe a bend at approximately 2400MHz, although less detectable to the eye.
Plot of experiment without BT watch
Plot of experiment with BT watch
Difference plot
Plot of cumulative differences
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