[amsat-bb] re antenna seperation.

Hi all, perhaps what appears to be a simple question but how far apart do I need to space a 6 ele X yagi for 2mtrs (1 wavelength long) and a pair of 12 ele X for 70cms (horizontally spaced and 3 wavelengths long each). The antennas are all homebrew and I know that as far apart as possible is the best solution BUT this is not possible so just how far should I be looking for as a minimum? I am trying to make sure that the de-sensing of any other radio equipment is kept to a minimum (no fancy rigs here, an old FT817 for 70cms and a FT-480r with a 25 watt linear when needed). regards Gus M0IKB