Because without that no-encryption rule, the ham bands would quickly turn into a commercialized free-for-all. The required openness prevents that particular class of abuse without ambiguity.
I'm a little puzzled by this argument, honestly. It's clearly an illegal commercialized free-for-all, so
- how would a viable white market develop? It would be patently obvious that the handy communications devices you're buying are using ham frequencies.
- on the grey/black market, why do we think that banning encryption is sufficient to dissuade illegal use but allowing it and banning commercial use would not be? It's already the case that FCC enforcement is very weak and there are a ton of newfangled digital modes. You could get by for a very long time sending encrypted transmissions on ham bands without anyone being able to stop you.
The amateur radio community already has a significant problem with unlicensed users on UHF and VHF, because cheap Chinese handhelds are widely marketed on Amazon and eBay with no mention of the fact that they're amateur-band equipment and require a license to use. If you search for "two-way radio" or "walkie talkie", most of the product listings make no distinction between FRS, MURS, GMRS and amateur band equipment. With wideband SDR devices falling rapidly in price, there is an impending threat to all licensed frequencies - it isn't illegal to buy or sell a HackRF One, but you can do a lot of illegal things with it if you're ignorant of or indifferent to the regulations.
FCC enforcement is light-touch and they don't have infinite investigative capacity, but they are more than willing to throw down a hefty fine if you're a flagrant violator. The encryption ban is essential in allowing amateur radio operators to monitor their own service; a large proportion of FCC enforcement actions are initiated in response to a complaint from another service user.
I get that some bands are legally restricted but it seems like the HackRF or other SDRs are not going to be a significant problem for widespread spectrum congestion any time soon. Why mention them?
There are protocols and sequences that mush be respected if you don't want to say "DDoS" a repeater frequency or diverge from band plans.
It's really common to have split frequency inputs on repeaters(+/- 600Hz or so on VHF) so even if a channel sounds clear you could be stomping on everything in a 40 mile radius. PL tones mitigate this somewhat but given the sparse, shared aspect of frequency allocations you want people who are properly educated.
I don't believe random numbers (certainly long strings of random numbers) would be an authorized transmission. They would serve no purpose allowed by Part 97.
