[4gotunameagain]

This does not magically increase the power radiated by an ethernet cable or somehow change the base frequency of the interference. Furthermore, the power levels are very low. If you check the link at the bottom, he is using a directional (Moxon) antenna to receive this faint signal. If this could somehow pose an issue with anything, it would have been caught in EMI testing of all network equipment sold

[avian]

As others have pointed out, EMC testing often only considers typical use and this is not one.

Another thing is that regulations don't only consider radiated power. Constant-level spurious transmissions are sometimes tolerated to a higher degree compared to modulated ones (e.g. in some bands maximum allowed interference is determined by quasy-peak level, not power). This is exactly because modulated interference (which is what this produces) is more harmful to communications systems.

[vvanders]

Part 15 is pretty clear that any harmful interference should be minimized[1]. Even though it's low power that doesn't mean that it still can't be picked up. Just because equipment is sold at retail doesn't give you a free pass on it.

Take powerline ethernet where the power levels are "low" but still can cause significant issues[2].

[1] http://www.arrl.org/part-15-radio-frequency-devices#Myths

[2] http://www.elmac.co.uk/RF_Emissions_of_Powerline_Ethernet_ad...

[jcims]

I think the issue is introducing a signal (particularly morse code) on a noise source that is typically steady state. I can pick it up pretty easily with just a bare UHF connector, no antenna.

Low risk overall but it's a good reminder.

[60Vhipx7b4JL]

It does not increase power. But it couples data instead of static noise into the communication which might be more annoying on the other end.

[JosephRedfern]

Does EMI testing consider "atypical" uses like this one? I'd assumed that they only tested normal use cases. I'd consider (wrongly, perhaps?) changing speed of a NIC several times per second to be an atypical use.

[londons_explore]

EMI testing only tests a product during typical use.

It's very possible to transmit illegal power levels with software mods, or even carefully crafted data packets in some cases.

[derefr]

> or even carefully crafted data packets

Unless you’ve made custom PHY hardware for those data packets to be pushed onto the line through, your data packets are going to be line-coded to ensure that the signal is self-clocking. Which basically precludes boosted harmonics.