[Repeater-Builder] newbie question: in and out problem

[Jay]

i am trying to build a simple repeater setup here in the philippines. i 
already have a home made C.O.R. receiver and transmitter and two 
antennas but 3 ft close to each other. the thing is when it receives a 
weak signal it goes in and out in transmitting it. can anyone give me 
an advice on how to fix this problem?