As invisible as radio signals then.

adrian_b 3 hours ago | parent | next [-]

In general, it is very easy to detect that radio signals are present.

A better comparison is with radio signals for which a method of spread-spectrum modulation has been used, chosen such as to have a bandwidth so wide that the averaged signal falls below the thermal noise level.

Such radio signals will also not be detectable without special detectors.

WiFi and Bluetooth use spread-spectrum modulation methods but they have relatively low bandwidths, so they can be easily distinguished from thermal noise. Much wider bandwidths are required to prevent detection.

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Hobadee 14 hours ago | parent | prev [-]

Now now... Let's be fair...

Radio broadcasts to everyone.

Light you can block off to a single direction.

Oh wait, directional radio antennas exist. Nevermind, yes. Exactly like radio waves.

	▲	TeMPOraL 13 hours ago \| parent [-]
		> Light you can block off in a single direction. Sorta, kinda. You're really only just attenuating things a lot. It's tricky to actually block it off fully. Same with radio waves, as light is literally the same phenomena as radio waves, it's just shaking faster.