UV is a bit higher than 10Mhz, so I stand corrected. But it didn't use an antenna as we are discussing, so, I dunno. I've got a bunch of secret squirrel stories but I would have people at my door if I told you.
A neighbor of mine who worked on secret squirrel "laser beam" stuff said his lab was working on UV vertical optical communications reflecting from cloud formations and atmospheric water vapor. There was an Australian hammy who built a pirate station using modulated mercury vapor lights to go quite a distance.