I'm planning to use a multiwave horizontal dipole oriented to work comms toward Alaska from Colorado. That ends up being awkwardly oriented to work east coast and Europe. If I placed a second identical dipole oriented more or less 90 degrees from the first one, how far apart would the antennas have to be to avoid perturbing radiation patterns between them? Obviously, only one would be in use at a time. I'm looking at an off center fed 7 band 135 ft dipole for this project if that makes a difference. The initial look at my property to mount them ends up creating a giant L with the ends being about 50 feet apart. I know if they are mounted more or less parallel to one another it will get interesting but I haven't seen anything about a perpendicular association. In a perfect world I would just put up a yagi or so but I don't have the ability to get that up and running.
Perpendicular dipoles don't interact at all, theoretically.
Of course in practice you won't be able to get them perfectly perpendicular, nor can you completely isolate common mode current on the feedline, but still the interaction is small enough to be negligible, especially considering a dipole isn't very directional to begin with.