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Comment by d136o | Hacker News Reader

Would love to know if anyone monitors their home or office RF spectrum for unexpected guests, or just for fun.

I’ve played around with hackRF and it seems like that type of scanning is something you might do in highly sensitive environments.

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I use https://github.com/merbanan/rtl_433 on the tire pressure monitoring system (TPMS) band used by my car (315 Mhz) to trigger home automation like turning on the lights as we're pulling up. (rtl_433 publishes to MQTT, which triggers actions in Home Assistant for certain serial numbers.)

Side effect is that it also logs the tire serial numbers of most (but not all) cars pulling into my driveway.

This is awesome! Makes for a nice little holiday project!

In order to get the TPMS to transmit on demand--at least on cars sold here in the United States--you have to send a 125 kHz signal out. The car does this periodically when it takes a reading, but unless you send this signal yourself, you won't reliably get a read as you're pulling up.

https://www.brakeandfrontend.com/decoding-tpms-wireless-sign...

The car (a Volvo) seems to ping the sensors at least once per minute when in motion, meaning there's pretty much always at least one ping once we're within range of home. It works perfectly for the home automation use case.

Not all cars can be triggered on 125khz and some cars transmit RF only when the car is not parked.

London underground does this with wifi, https://www.wired.co.uk/article/london-underground-wifi-trac...

I do! I ingress into a time series DB.

But because I actually have a bunch of RF-emitting sensors (the Wi-Fi stack pulls too much power and ZigBee/Z-Wave licensing is too much $$, although my data is not authenticated).

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