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Actually there are rules, at least in Germany, and I assume the same is true for the US. You can use a microwave heating gun, i.e., a device that shoots a beam of microwave energy to serve similar to a leaf-blower sized hair dryer, in the ISM band(s), which might be able to saturate the LNA in 2.4 GHz radios (depending on where it is placed relative to the band-pass), but you are not allowed to use a broad-band, not-caring-about-others telecommunications radio on the same frequency. For some lower frequencies I could use them to transmit power via a resonant, one-wire transmission line to a quadrocopter to save on the weight of insulation, possibly by using aluminium-clad single mode fibers to get data capacity at the same time, so I can reduce the weight of the tether reducing overall power usage, weight and size, but if I were to use the same frequency for a direct-sequence-spread-spectrum (GPS-style) radio-location-beacon network, that would not be allowed, or only within certain restrictions usually based on both EIRP/PEP/PA-in power and techniques that allow for friendly coexistence between users of the same spectrum, i.e. with CSMA/CA or restrictions to send only 1% of the time, averaged over e.g. 24h or so.

Yup, just because it's an unlicensed band doesn't mean there aren't other restrictions on it.

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