Magnus Danielson wrote:"I would let the low-frequency PPS act as start and the 10 MHz as stop, unless you want to measure the PPSes directly." I tried that too. Seemed to work perhaps a little better. I ended up using the 1 PPS from the Z3801 instead of the 10 MHz. I am going to have to dig out that Tbolt just to verify that the test set up is OK.