Ferrite cores, or even removing the IR Blasters entirely, has no effect on my MRF100A V1.0. With no wires attached except power, it acts very much like an electronics-detector; status light illuminating near any A/V device. Removing antenna (or holding it) helps a bit, but not enough. Only distance from all electronics seems to help. Having the blaster wires with lots of other wires doesn't appear to have much impact. (And I have a doozy of a bundle going through a conduit for about 8 metres, connecting the A/V electronics to the monitor, speakers, powered subs, ButtKickers, CAT5, etc.)