Hi Sounds very normal to me.
The EFC voltage can be converted directly to a frequency change. There are enough variants of the 10811 that checking what you have is probably the best idea. A good guess is that it tunes 0.2 ppm over the full EFC range. To check the OCXO - break the loop, hook up a counter and take the EFC to each end of it's range. Lastly, ground the EFC. The three readings should give you a good idea of the gross sensitivity of the 10811 you have. For a more accurate number, step off the voltage in 1 volt steps and measure the frequency at each step. Yes, you need a counter to do the measurement. It does not have to be anything super fancy. It does need to be able to "see" 1x10^-8 at 10 MHz. With a computing counter not to hard. With a conventional counter, you need a gate time of 10 seconds or more. Bob -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Chris Howard Sent: Monday, November 05, 2012 9:49 AM To: Time Nuts Subject: [time-nuts] getting a grip on 10811 drift (beginner-ish question) I built a GPSDO using my own power supply, a VE2ZAZ board, a Trimble Resolution T GPS and a surplus HP 10811 oscillator. I'm having a bit of trouble with it. I have it set up and it locks ok and stays in lock so far. But the recommended long-term integration setting is not working for me. I think it is about 3 hours. At the end of every cycle it does a control voltage adjustment, always in one direction. If I understand it right, the oscillator is slowing and needs an incremental bump downward of control voltage every time. That seems like it is more than just long term drift. But I don't have my head around the quantities I'm looking at. I can measure the control voltage change over time. Can I convert that into a frequency drift? Or do I need to stop the voltage adjustments and allow the drift to occur then do a measurement of that directly somehow? Is this type of behavior an indication of dire problems with my 10811 oscillator? Chris Howard w0ep _______________________________________________ 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. _______________________________________________ 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.
