[amsat-bb] Tone interference

[Louis House, KD5GM]

I have discovered a pulsating tone (about 600 HZ) in my 910H receiver when I am tuned to 145.900 MHz (working the Linear birds VO-52 etc).  The tone stops when I power off the G-5500/LVB tracker.  All equipment is grounded and ferrite core filters are on all of the cables to solve this problem.  Aside from moving all equipment across the room from each other, what might I be missing?
Any help will be  appreciated
Thanks, 
LOUIS, KD5GM in EL29kq
CW, The original digital mode
AMSAT #37061: FIST #3606