Herbert, If you find my original post and also look at the HP5065B info on leapsecond. com you will find that the pre/post performance is closer to that listed below. I belive Luciano missread the plots! Cheers, Corby Dawson Typical ADEV improvement Seconds Before After 1 1.4x10-12 4x10-13 10 4.0x10-13 2.1x10-13 100 1.2x10-13 6.0x10-14 Note: C.Dawson measurements