This is a subject that I am sure will garner a lot of varied response... so here's my two cents worth. If it is possible to maintain a trace to trace spacing of at least 2 times the trace width routed over an intact ground (or power plane) then guard bands are not overly effective in preventing cross-talk. If your layout will not lend itself to that large of spacing then guard bands can be useful. Jeffrey A. McGlaughlin PCB Designer Battelle Memorial Institute Columbus Ohio [log in to unmask] -----Original Message----- From: Hawes, Adam [SMTP:[log in to unmask]] Sent: Tuesday, 27 July, 1999 04:08 To: [log in to unmask] Subject: [DC] Ground Shield Tracks I feel sure this is probably an issue for a lot of PCB designers...... 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. I was under the impression that ground tracks only served a useful purpose on 1or 2 layer boards and that on a multilayer they were essentially a waste of space as most of the capacitive coupling would be straight to the ground plane. I don't like to tell the engineers their jobs obviously so can anybody put forward their views so I have a more solid argument! Thanks all, Adam Hawes PCB Design Eng. GenRad Ltd. Tel: 0161 491 9290 Fax: 0161 491 9106