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Microcasting Color TV By Abusing a Wi-Fi Chip (hackaday.com)
szczys writes: The NTSC standard has effectively been replaced by newer digital standards, but most televisions still work with these signals. This can be done through a composite video connection, but more fun is to broadcast video directly to your television's analog tuner. This is what cnlohr has been working on, using a lowly ESP8266 module to generate and transmit the color TV signal. This board is a $3 Wi-Fi module. But the chip itself has a number of other powerful peripheral features, including I2S and DMA. This hardware makes it possible to push the TV broadcast out using hardware, taking up only about 10% of processor time. Even more impressive, cnlohr didn't want to recompile and flash (which is a relatively slow process) during prototyping so he used a web worker to implement browser-based development through the chip's Wi-Fi connection.
Speaking of chip-abuse in the interest of hyperlocal signal propagation, reader fulldecent writes to point out a project on GitHub that "allows transmission of radio signals from a computer that is otherwise air gapped. Right now this could be useful for playing a quick tune or for pranks. But there are more nefarious uses as this could also be used to exfiltrate information from secure networks."
Agreed - cool hack.
There *should* be a big, huge warning, though - about violating FCC rules. The hack broadcasts on restricted frequencies; replicate at your own risk.
If you are relying on Part 15 FCC regulations, be sure to read them first. Using a device in a way not contemplated by the manufacturer can turn your "approved" device into a "home-built transmitter [that is] not for sale" which puts the onus entirely on you to comply with the rules.
Having said that, if nobody complains, then you almost certainly won't be hearing from the FCC, and even if you were to use a device "as intended" and it caused harmful interference, you are still required to cease using it.
https://www.fcc.gov/Bureaus/En... has an interesting item on page 7:
With the exception of intermittent and periodic transmissions, and biomedical telemetry devices, Part 15 transmitters are not permitted to operate in the TV broadcast bands.
I guess that means if you are only going to transmit "intermittently" or "periodically" then this is fine, but it's probably not okay to use this for your home-security system that runs 24/7.
Channel 3 is in the 54-70MHz band, which is okay but only at very low power, 100 microvolts/m measured at 3 m away ("quasi-peak").
It is almost certainly legally safe to use this over low-VHF channels over coax rather than "over the airwaves," and you'll probably get a stronger signal to boot. But it won't be as much fun.
There may be some opportunity to use this under other parts of the FCC rules, such as part 18 (industrial, scientific, and medical) and, on applicable frequencies, part 97 (amateur radio license-holders only, and only in ham bands, and even then NTSC is not an acceptable "mode" in many bands).
Knowledge is how to play a game, intelligence is how to win, wisdom is knowing what game to play.
your car's starter motor violates FCC rules when the brushes get old, so you too will join the others in the gulag for violating the rules
The phrase "intentional radiator" has a significance here. Google it if you are confused.
It would be a good question to research if this intentional radiator met the limits of a Part 15 device, like the unlicensed AM and FM broadcast transmitters that you can buy or build.
It would be a good question to research if this intentional radiator met the limits of a Part 15 device, like the unlicensed AM and FM broadcast transmitters that you can buy or build.
FCC OET Bulletin No. 63, October 1993:
With the exception of intermittent and periodic transmissions, and biomedical telemetry devices, Part 15 transmitters are not permitted to operate in the TV broadcast bands.