Wes Stewart, N7WS wrote:
"Do not no.."

6-ft seems sufficient separation at 2-meters or 70-cm to avoid tight
coupling.

First MW BC plant I worked in was in 1949. It had stations at 950 KHz
and 1320 KHz. Both stations used the same antenna tower. Pass / reject
filters kept them out of each other`s final amplifiers.

I think in the VHF / UHF range one might get lucky and select the right
length of coax between an individual antenna and the common feed point
where individual antennas are paralleled and make the antenna at that
point look like a high imprdance to the wrong transmitter. For practical
purposes the wrong antenna disappears, but the right antenna does not.
It matches the coax.

Best regards, Richard Harrison, KB5WZI