I measured the phase-noise of an Ettus OctoClock distribution amplifier. These plots compare it to earlier measurements on an SRS FS710 and a Symmetricom 6502 as well as my own TADD-1 inspired AD8055 prototype.
OctoClock schematic here: http://files.ettus.com/schematics/octoclock/octoclock.pdf
10 MHz clock-distribution chip: http://www.ti.com/lit/ds/symlink/cdce18005.pdf
For time-nuts kind of stuff (H-masers!) the 10 MHz phase-noise doesn't look that great, and there is something funky going on in the AM noise!? The box is powered by a +6 VDC wall-wart PSU which is probably the cause of all those spikes...
The PPS-channels are based on 7404 hex-inverters and look OK. 200ps of skew is equivalent to 4 cm of trace-length (?) - which seems like a lot if there was an effort to minimize it... For a 1 V/ns rise-time pulse 200ps is equivalent to 200mV of DC-offset in either the signal or the counter trigger-level which also seems like a lot?
