[Repeater-Builder] 450-460mhz Repeater Co-Channel Interference

[ptt_pupil]

Can anyone tell me if there are ANY fixes for co-channel interference? 
What is the use of a PL tone if it isn't able to block out the co-
channel users? Is it because the co-channel user is transmitting with 
more power and is able to break the PL tone? What are the expectations 
of a PL tone? When does it work and when does it not work? Are there 
other devices that can help all? Thanks in advance!