Maybe there is a niche for "license free" radio communications as a hobby? It could operate at two levels. The first level is to operate completely inside the

Maybe there is a niche for "license free" radio communications as a hobby? It could operate at two levels. The first level is to operate completely inside the rules. The rules don't say that a device can't radiate, just that it has to be within very strict "unintentional radiator" limits which are judged to produce negligible interference. How far can communications be pushed within these limits? The second (more risky) level is to operate on the basis of living within the spirit of the law, but not the letter. The spirit of the law is that you shouldn't cause any interference. At this level, you transmit, but in such a manner that you never interfere with anyone else. How do you do it? That's why it would be an interesting hobby, as it would be truly state-of-the-art. (Think cognitive radio on steroids.) The fact that you don't get caught would be a metric of success: in the best case that your transmissions have never been detected, or in the worst that you haven't interfered with someone and prompted a complaint. Of course if you mess up you're in it big time.