You cannot have 2 (or more) antennas that transmit simultaniously that close. If one recieves, or they are used at seperate times, you can mount them that close. Usually best to mount everything by itself, though.
1 AM/FM or scanner & 1 transciever is OK
2 different transcievers is OK (CB & HAM), but may not be ideal (or be used at the same time, either/or kind of deal)
and a scanner & AM would be fine
2 cophased antennas of nearly any band would not be OK
“Coming of age in a fascist police state will not be a barrel of fun for anybody, much less for people like me, who are not inclined to suffer Nazis gladly and feel only contempt for the cowardly flag-suckers who would gladly give up their outdated freedom to live for the mess of pottage they have been conned into believing will be freedom from fear.”