# Hobbyist estimates walking speed of 1.3 m/s from a local TV station signal using a simple radio receiver

- Published: 2026-11-10 14:20 UTC
- Section: Science › Instruments & experiments
- Tags: motion detection by radio signal, selective fading, TV signal spectrogram, WiFi sensing, LTE motion sensing, walking speed measurement, wideband radio signal, multipath reflection, radio receiver experiment
- URL: https://realtech.media/news/rt-d7515888fc0ce80603f9f20c_hobbyist_estimates_walking/

**In a home experiment, a simple receiver picked up a person's movement as fading stripes on a TV signal spectrogram. According to the author, WiFi and LTE work the same way.**

![Hobbyist estimates walking speed of 1.3 m/s from a local TV station signal using a simple radio receiver](https://ecosistemastartup.com/wp-content/uploads/2026/11/wifi-sensing-deteccion-movimiento-tv-1200x675.jpg)
*ecosistemastartup.com*

The author of the blog maurycyz.com recorded the signal of a local TV station with a simple radio receiver and showed that a person's movement can be seen in it and used to estimate walking speed [1]. The signal was displayed as a spectrogram (a waterfall) with an update rate of 150 Hz [1]. This is a home demonstration, not a finished device.

## Selective fading as a motion sensor

Walking between the receiver and the TV station caused only a slight disturbance of the signal [1]. After the author moved the antenna by a few centimeters, the picture changed: selective fading appeared, in which the direct signal is cancelled by a strong reflection [1]. The phase of the reflection depends on frequency, so the effect is not uniform across the whole signal [1].

In this state the signal is extremely sensitive to any nearby movement [1]. The author recorded the change when he got up from his chair, and then while walking around in a neighboring room. In both captures the spectrogram showed stripes with gaps between them [1].

## Speed from the stripe spacing

The gaps appear when the reflection from the body perfectly cancels the residual signal. This happens each time the path length changes by one wavelength [1]. The distance between stripes was about 70 pixels, and the waterfall updated at 150 Hz [1]. That gives an interval of about 0.47 s between gaps, or 2.1 Hz. Multiplying by the speed of light divided by the 490 MHz carrier frequency gives 1.3 m/s.

The author was walking perpendicular to the direct signal path, so the speed can be used as is, without a correction for geometry [1].

According to the author, a simple receiver can therefore detect motion and give an estimate of its speed. The method is not limited to TV: any wideband radio signal, including WiFi and LTE, can be used in much the same way [1]. Such signals make worse demonstrations because their waterfall is messy, but the same data can be extracted from them with some additional work [1].

## Sources

1. [maurycyz.com](https://maurycyz.com/projects/fading)
2. [ecosistemastartup.com](https://ecosistemastartup.com/tu-tv-detecta-movimiento-el-wifi-sensing-ya-es-real)

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Source: RealTech, realtech.media — https://realtech.media/news/rt-d7515888fc0ce80603f9f20c_hobbyist_estimates_walking/