OK, I'm puzzled. Can someone with a good knowledge of OCXOs explain my observation. This is my HP 106B double ovened quartz oscillator, but I'm sure the theory applies generally.
It's easiest to show these observations as made-up but approximate numbers an hour apart. Say the device is set to 5.000 000 000 MHz and then measurements are done on a 5370B with a GPSDO as an external reference. (Note that the 5370B has more jitter than shown below when measuring frequency, but by following it for a minute or so you can see what numbers it hovers around.) Connect an HP rubidium (to prove it's not a measurement error): Hour 0 1 2 3 4 5 5.000 000 000 5.000 000 000 5.000 000 000 5.000 000 000 5.000 000 000 5.000 000 000 My 106B as it currently is running: 5.000 000 000 5.000 000 001 5.000 000 002 5.000 000 003 5.000 000 004 5.000 000 005 If I turn the inner oven control in one direction (presumably the hotter way) a fraction of a turn and then sit back and watch: 5.000 000 000 5.000 000 003 5.000 000 006 5.000 000 009 5.000 000 012 5.000 000 015 If I turn the inner oven control the other way (a bit further past the original point): 5.000 000 000 4.999 999 995 4.999 999 990 4.999 999 985 4.999 999 980 4.999 999 975 What I don't understand is why changing the oven temperature cause the frequency to continually increase or decrease. If you look at Quartz temperature curves (and I'm presuming this is an AC cut since SC wasn't invented until 1976) they show a frequency offset dependent on temperature. But I'm not getting an offset, I'm getting a steady increase - all the time. Sure I can find my sweet spot where it moves minimally (as it is now) but that is hard to improve and seems to be sitting on a knife edge. The only other thing to note is that my power supply rail is a few volts too high (see previous post). Could this be the cause? If what I'm seeing is normal I'd love to have it explained to me! Regards, Jim _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
