problem in improving return loss of dipole antenna

hi all,
i m working on yagi uda antena.so first i have to make a dipole for this. but i m facing a problem in its retun loss .my measured RL is -9db but one of my friends told me that it should be -30 to -35db. plz help me
how to improve it?

How did you feed the dipole? with a balun?

you have to do it with the reflector and directors elements. because they are also part of
the antenna, with the coupling between them.