[Amps] problem with pll lock with modulation

[tzikas tzik]

hi. i have a transmitter 500w. When i give modulation to the pll i have
problems with pll's lock. i believe that the problem is from modulation's
coaxial audio cable. I think that it works like an antenna and receive R.F
from the inverted-L antenna and causes this problem. What do you propose to
do to resolve this problem. A choke in series with modulation cable it will
helps? Or something else? Here you can see a schematic from transmitter's
installation.
http://tzitzikas.site90.net/files/installation.JPG
Thank you very much!

callsign: sv1bln
Athens