I would power your VFD from a RFI filter such as this one http://www.ebay.co.uk/itm/RASMI-14A-...YAAOSw~OVWyKNV and put ferrites on your PP cable at each end - like these http://www.ebay.co.uk/itm/20-Pcs-Gra...oAAOSwCypWpz6J but you won't need 20 of them and you have to get ones that fit the cable.

Anyway - general question - Anybody know ? - do the better quality VFDs have RFI on the mains input ? and do the Chinese ones not have it ?

Hope this helps,

Cheers,

Rob