No, if it's moving left to right the OCXO is low (I just had my coffee). Joe
-----Original Message----- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of J. L. Trantham Sent: Sunday, July 25, 2010 7:05 AM To: 'Discussion of precise time and frequency measurement' Subject: Re: [time-nuts] Basic question regarding comparing two frequencies The only problem with the lissajous approach is you can't tell if your OCXO is high or low relative to the reference figure. This is resolved by triggering the scope with the reference. If the trace is moving left to right, the OCXO is high, and vice versa, IIRC (I just woke up). Otherwise, it works fine for fine adjustments aligning an unknown oscillator to match a known reference. Joe -----Original Message----- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Geoffrey Smith Sent: Sunday, July 25, 2010 2:58 AM To: 'Discussion of precise time and frequency measurement' Subject: Re: [time-nuts] Basic question regarding comparing two frequencies Mark, I have been measuring the difference between a GPSDO and a HP 10811A TCXO. To avoid any triggering issues I put the CRO into XY mode. The resulting Lissajous curve figure flips at the rate of the frequency difference good old Wikipedia has the maths. Just sit and watch the Lissajous and you can adjust the TCXO to have the not flip and set accuracies in small fractions of a Hertz. Geoff -----Original Message----- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Mark Spencer Sent: Sunday, 25 July 2010 3:29 AM To: time-nuts@febo.com Subject: [time-nuts] Basic question regarding comparing two frequencies Hello: Just for grins I decided to compare the frquency from my GPSDO to the time base in my 5328A counter. I connected the 10 mhz time base from the counter to channel A of my 100 Mhz scope, fed the 10 mhz signal from my GPSDO into Channel B and with a T adaptor also fed this signal into the input of the counter. I scope to trigger from Channel B. The drift betwen the two signals on the scope seems to match the error in the displayed frquency on the counter. (ie. if the counter shows 9999.9998 it takes approx 5 seconds for the the wave form on channel A to slip a full cycle realitve to channel B.) Is this a reasonable approach or is there a better way to compare two frequencies using a scope ? Best regards Mark Spencer _______________________________________________ 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. _______________________________________________ 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.