Although it's not an issue for the OP, I found that the Pi's i2c bus is very susceptible to RF. Note that at VHF or UHF frequencies, an i2c ribbon cable of an unfortunate length can be especially troublesome. Since there was no good solution using a ferrite, I bought some fine copper mesh on eBay to put the Pi and its i2c-connected devices inside a Faraday cage. This worked. The long-term solution, though, was to use USB-connected devices instead of i2c-connected devices. USB isn't impervious to RF either, but its natural noise immunity appears to exceed i2c's.?
73 Chuck K4RGN
Chuck K4RGN