Topband: EY8 RFI Problem

[Ken Claerbout]

  I'm headed back to Tajikistan on the 23rd of this month.  Nodir EY8MM and I will be focusing on 160 during this time as announced in W3UR's Daily DX and posted on Nodir's web page http://www.ey8mm.com/index.php?page=lowbands  His lowband QTH is in a research center outside of Dushanbe.  Unfortunately he has been dealing with a nasty RFI problem involving some of the research equipment.  The problem looks to be narrowed down to a 30 meter long USB cable, which runs through a few "USB extenders" in order to drive the length of the cable.  I don't know if the cable is shielded.  Nodir has tried some ferrite beads with limited success.  I'm going to be taking more ferrite's with me but we were also considering a USB optical extender that would provide isolation.  I wonder if anyone has dealt with a similar problem or if there are other things we should try?  If anyone has a spare USB optical isolator pair lying around that I could take along and try, it would be greatly appreciated.  I'm a little reluctant to buy a pair, which are pricey, without knowing if they will work.  Resolving this RFI issue will go a long way towards ensuring Nodir can continue his lowband operation from this wonderful QTH.

Thanks
Ken K4ZW