KBOO didn't purchase any spectrum, let alone double spectrum. They're a noncommercial station, which means they're not subject to application or regulatory fees

KBOO didn't purchase any spectrum, let alone double spectrum. They're a noncommercial station, which means they're not subject to application or regulatory fees. They have the rights to what every station on the FM dial has, except possibly FM translators/repeaters: 200 kHz analog signal centered on 90.7, and 100 kHz on each side of that for the HD signal, for a total of 400 kHz. So their signal starts at 90.50 MHz and ends at 90.90 MHz. The 90.5 MHz pirate was operating on top of the licensed 90.7 signal. (I should note that you're correct about the guard bands with calculations to avoid harmonics, intermodulation products, images, etc)