[Repeater-Builder] Antenna Question

[Christopher Hodgdon]

We are looking at setting up a basic (I know there is no such thing)
repeater.  What I need to know, if you do not have a duplexer to run
your antenna through, but have two antennas, with one on the TX and
one on the RX how far apart do they have to be to be able to correctly
operate?