This is the method I use for my 5110. There are two 10 mhz outputs on the osc - you can unplug one of the plugs and use a 10x probe there. My unit will hold a couple of parts in 10-8 for months.
73, Bill, WA2DVU Cape May, NJ -----Original Message----- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of J. L. Trantham Sent: Tuesday, May 07, 2013 11:52 PM To: 'Discussion of precise time and frequency measurement' Subject: Re: [time-nuts] OCXO Adjustment Question Fred, What I do is to apply the GPSDO to the trigger input of a scope and the output of the OCXO to be adjusted to the vertical input of the scope. Set the time base to something line 100 nSec or faster and watch the output of the OCXO after it has warmed up for 30 minutes or so. This is an option only if you have an output from the OCXO you can watch. If no output, try a x10 probe attached to a 10 MHz connection from the OCXO inside the monitor. However, be careful that the probe does not 'load' the OCXO and shift the frequency. Adjust the OCXO for a stable display, not drifting left or right. If the sine wave (or square wave) is moving to the left, the OCXO is high in frequency. If it is moving to the right, the OCXO is low in frequency. If stable, it is matched to the GPSDO. This is useful as long as the OCXO and GPSDO are within a few Hz of each other. The amount of time it takes for the display to shift 1 cycle tells you how close the OCXO is to the GPSDO. For instance, if it takes 10 seconds for the display to shift one cycle, 100,000,000 +/- 1 cycles went by in that 10 seconds or 1 part in 10E9 if I have my math correct. Joe -----Original Message----- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Frederick Bray Sent: Tuesday, May 07, 2013 9:25 PM To: Discussion of precise time and frequency measurement Subject: [time-nuts] OCXO Adjustment Question This might be slightly off-topic, but probably there is a time-nut who knows the answer. I am trying to adjust the 10 MHz OCXO in a Cushman 5110 service monitor. I am using a frequency counter driven by a GPSDO. Perhaps someone can educate me about a couple problems I am encountering. I tried making small incremental adjustments but after I am done, the frequency drifts several Hz and then re-stabilizes at a new value. When I make further adjustments, I notice strange behavior. For example, if I initially turned the adjustment clockwise to increase the frequency, it will now decrease if I turn it clockwise and increase if I turn it counter-clockwise. On the next adjustment, it will reverse again. Is there some correct procedure to adjust an OCXO? Many thanks for any suggestions. Fred Bray _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
