Has someone already done the work and plotted TDEV or phase Dev for a run of the mill GPSDO. Particularly for a GPSDO with a non-exotic oscillator.. Or, perhaps the USRP flavor? There's a fair number of Modified ADEV plots out there from time-nuts and others, so I can calculate it, but hey, if someone has done the work for me, I'm lazy. http://www.leapsecond.com/museum/manyadev.gif for instance, tells me that at 1000 seconds, a TCXO has MDEV of around 1E-9, so TDEV of about 0.6 microseconds, and a Z3801 (MDEV 0.5E-11) has a TDEV of 3ns.