I'm assuming he also didn't account for harmonics. It'd be interesting to see how dirty his transmissions made the spectrum.

Given that he took out 315MHz in a pretty wide area, I'm wagering he was using a specific 315MHz module and was just transmitting a near-constant signal. (A duty cycle issue rather than a harmonics issue.)

Something like this: https://www.aliexpress.com/item/NEW315mhz-rf-Transmitter-and...

Also don't rule out an incredibly poorly made 315Mhz transmitter. Chinese companies will see lots of bad reviews on their 315Mhz breakout board like, "Terrible product! Only works from within like 3 feet from the transmitter."

So management gets mad at the engineer (who likely has no formal training or knowledge of FCC regulations) and says, "fix it!"

"OK OK I'll just crank up the power!"

Version 1.1 of the board is released on AliExpress a week later ("New version of board. We fixed weak signal!").

End users start getting the new board and like magic they can pick up a signal from like a mile away!

Then the FCC comes knocking?

FCC can’t really do anything about a Chinese person selling from China

They can if someone is importing it.

Most hobbyst (at least where I live) order directly from China on ebay or aliexpress. It's cheapest this way.

Customs services worldwide probably won't even come close to inspecting even 1% of that unending stream of tiny plastic envelopes containing some sort of electronics heading for thousands of local hobbyists. It's a logistical impossibility.

They could blacklist everything and only pass-through stuff sent by trusted exporters I guess. Check 1% of the packages, if some exporter lied revoke his trusted status.

But I highly doubt they will do it :)

That's what I do it almost all my equipment (not US, though)

They can send a BOLO to CBP and have the devices seized on import.

HAHAHahahahaa.

An entire bucket of Chinese electronic components in my living room begs to disagree.

Modules and components do not need FCC certification to be imported. CBP isn't going to do anything.

Finished goods need FCC certification to be sold.

Why do you assume there was a microprocessor involved at all? Most PIR sensors come as modules that operate either with a normally open or normally closed trigger pin and a couple of pots for adjusting sensitivity and trigger duration.

It would be easy to build a transmitter to blast out a constant high pulse and then just cut it off using a transistor or mosfet hooked up to the trigger on the PIR.

Simple circuit with no microprocessor or coding required.

Like all the best projects.