[Repeater-Builder] Antenna Spacing

[georgiaskywarn]

How close can these antennas be placed in the same horizontal plane?  These 
antennas would be placed at the top of a tower on one leg.  


A) db224 on 2mtrs and db224 on 220mhz

or

B) db224 on 2mtrs and db420 on 440mhz

Thanks,
Robert