This is a spectogram of the indication from a local TV station:
Walking between the receiver and TV position causes a minor disturbance to the signal, but it's nothing to compose residence about:
For this capture, I moved the antenna a few centimeters:
This is selective fading: The straightforward indication is being canceled out by a powerful reflection. Because the phase of the consideration depends on frequency, this consequence is not uniform complete the entire signal. Apart from being annoying if you're trying to observe TV, this province is extremely delicate to any nearby movement.
Here's what happened to the indication whenever I got up from my chair:
... and here's me strolling about in a neighboring room:
The gaps between the stripes happen whenever my consideration absolutely cancels out the residual signal, which happens all period the way dimension changes by one wavelength. Let's use this to fig out how accelerated I was walking:
The gap between all stripe is about 70 pixels, and the waterfall has an update charge of 150 Hz...
70 pixels * 1 second/150 pixels = 0.47 seconds = 2.1 Hz speed of ray / 490 MHz * 2.1 Hz = 1.3 m/s = 4.6 km/h
I was strolling perpendicular to the straightforward indication path, so the speed can be used as is, without any adjustments for geometry.
So, a uncomplicated broadcast reciever is capable to detect motion and provision an estimated speed — and it's not fair TV that plant for this: any wideband broadcast indication akin WiFi or LTE can be used in much the identical way. Those create worse demonstrations since they have a messy waterfall, but it's imaginable extract the same data alongside a bit of work.
Happy paranoia!
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