trevwhite, you state: “I am getting 9.9999996Mhz on the counter.” What I showed on my counter using the math function was
9,999,999.6 Mhz PM6666
10,000,000.00010 Mhz CNT-81
and the GPSDOs I’m using and my counter give me confidence in my readings. To get better resolution than your counter can display try triggering your scope on the REF 0 and set the timebase to around 10 or 2ns/div. Connect the 10Mhz output from your counter to the vertical channel and watch the waveform drift left or right. There isn’t an actual output on your counter but a cable from the REF in to your scope may have enough leakage to pick up the signal if the scope is set to some low MV range. The drift will be superimposed on a waveform that is mostly noise but will allow you to see the drift. The .4Hz low your counter is displaying should show a fairly fast drift to the right of the screen. If your counter has a reasonable timebase you can first adjust your 9,999,999.6 reading to as close to 10Mhz as possible then use the scope method to get it closer.
If you have connected the REF 0 the way it was in the article you referenced then the GPSDO you’ve created should be the more accurate of the two. If you use the Lady Heather software and connect a serial cable to the J8, DIAGNOSTIC jack on the front you can use RS-232 to create a graph similar to the one I created that will give you a lot of information on stability and accuracy of the Lucent unit. If you use the following connections you can use RS-232 instead of RS-422 and it seems to work o.k.. It’s also a good idea to leave the output level switch in the 17 position.
PC RFTG
DE-9S DE-9P
5 <----GND--->7
3 TXD -------->8
2 RXD <------- 9