One of the more interesting scientific studies I have seen on this subject was published in the proceedings of the PCB Design Conference, and I have never seen it reprinted anywhere else. The author built boards with every different configuration of pairs of parallel traces separated by grounds and open spaces, and then drove them at different frequencies to measure crosstalk. For example: G=ground, o=open space, tested at 100KHz -++- -65 -+o+- -75 -+G+- -89 -+oo+- -80 +-+- -65 +-o+- -75 +-G+- -89 so adding a space between the pairs resulted in 10db reduction in crosstalk, but making it a ground reduced an additional 14db I can't reproduce all of the tables here, and I only saved the "results" pages so I don't know which year it was (sorry), but if you seriously want to find it I can tell you it was on page 146, course number 105 called Analog Design and it was NOT in 1993, 1995, 1996 or 1999 Good Luck Jack -----Original Message----- From: Hawes, Adam Recently, I have come across an increasing number of engineers who wish to have certain tracks on multilayer PCB's shielded by ground traces running adjacently. It seems to be a case of jumping on the bandwagon to me because we never used to do this until about 12 months ago. Adam Hawes PCB Design Eng. GenRad Ltd. Tel: 0161 491 9290 Fax: 0161 491 9106