There is a strictly experimental specialty within ham radio called "VHF/UHF DX'ing". Or, translated: point-to-point communications over long distances at radio frequencies not normally capable of this. It's sort of like trying to pick-up an FM radio station from a town 200-300 miles away, 'cept these guys are doing it in multiple frequency bands, from near TV Channel 2 (50 MHz) to microwaves (10 GHz) and higher.
Several times a year they have "contests", which is basically an excuse to get everybody on the air during a designated period. The object is to collect as many confirmed 2-way communications as they can, on as many frequency bands as they can, between as many locations as they can. It's very challenging, both logistically and technically.
Most of the time they do this from home-based stations, but guys like the one with that Subaru operate "rovers". Their task is to drive to places where there is nobody else with a home station so the "grid square" - a coordinated map square, basically - can be added to the contest participants' scores. The Subaru is a popular platform for this because rover work usually involves off-roading to mountain tops on very poor access roads.
Looking at the picture, this guy is covering what we euphemistically call "DC to daylight" - a very broad range of frequencies. I see at least 7 different bands not including the dish, and it is probably setup to handle at least three bands up to 24 GHz.
FWIW, noting the tag, California has more hams per capita than any other state.