As such, what you're suggesting is illegal in the US, unfortunately.
To clarify, not illegal to posess but illegal to use.
Like clockwork, I get this boilerplate line every time something like this is brought up. However, there are a couple counterpoints:
-> Many FCC rules are outdated or aren't enforced. For example, many junky cheapo Chinese gadgets have little to no protection from creating RF interference, yet are sold by the truckload on sites like Amazon. However, this creates a bit of a problem. If they exceed designated levels of interference creation, are the standards too low or are the gadgets incompliant?
-> If the mythical black vans come by and spy on your RF activity, then that could be inadmissible/illegal by a certain amendment(s) in the US constitution.
-> If used properly, incompliant RF gadgets are undetectable with respect to a normal operating environment. If you blasted TDWR-range WiFi in a concrete room, nobody would ever know except for the devices located within it.
-> Due to the coronavirus pandemic, many places are still in a lockdown phase and I bet there's no RF spying happening here.
-> If the FCC requires certain code to be put into RF devices to prevent certain frequencies from being used, this is a violation of another amendment in the US constitution, so we'll always be able to use the hardware to its fullest potential if needed, unless hardware-level restriction are created.
Until we fix the RF regulatory landscape, Superchannel is the new Superman.