Merc Vapor create a single spike per 120hz and stay on longer. This can be seen by using win media player in the Bars & Wave: Scope mode. Although this shows you a view of the noise about 4 times more than needed for 60hz. Michael C Martin RFI Services 6469 Old Solomons Island RD Tracys Landing, MD 20779 240-508-3760 mike at rfiservices.com www.rfiservices.com