Re: [time-nuts] FE5680 DDS plot
On 02/06/2012 02:56 AM, Bob Camp wrote: Hi I suspect it's a linear compensation of a temperature effect that's actually higher order. Depending on exactly where you are it could be a good thing or a very bad thing. I have seen examples of both … Indeed. If you sit tight the detectors resolution will be more of an issue than anything else. Cheers, Magnus ___ 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.
Re: [time-nuts] FE5680 DDS plot
Hi I suspect it's a linear compensation of a temperature effect that's actually higher order. Depending on exactly where you are it could be a good thing or a very bad thing. I have seen examples of both … Bob On Feb 5, 2012, at 9:02 AM, Magnus Danielson wrote: On 02/02/2012 06:15 AM, Scott Newell wrote: Javier Herrero's exciting DDS discovery led to this plot of the unit tweaking the frequency (cmd 0x22): http://n5tnl.com/time/fe-5680a/graphs/dds_autotuning.png It appears to make an adjustment even before lock! It is interesting how the DDS frequency compensates the temperature. Should mostly improve performance on start-up or unstable thermal situations, but be of fairly low improvement on static conditions. Cheers, Magnus ___ 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.
Re: [time-nuts] FE5680 DDS plot
Great plot :) I've a dump of the SPI transfers during a night taken with the logic analyzer... but have found no time yet to process the dump to extract the transfers. Of course it is easier to take it from the serial port data :) The adjustment looks quite closely related to the temperature. Regards, Javier El 02/02/2012 06:15, Scott Newell escribió: Javier Herrero's exciting DDS discovery led to this plot of the unit tweaking the frequency (cmd 0x22): http://n5tnl.com/time/fe-5680a/graphs/dds_autotuning.png It appears to make an adjustment even before lock! ___ 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.
Re: [time-nuts] FE5680 DDS plot
I forgot... have you had the opportunity to check if the difference between the two DDS programming words is the same in all cases? All my readings leds to 1400.00x Hz, I've not looked at it but probably the difference in DDS counts is constant. Regards, Javier El 02/02/2012 10:13, Javier Herrero escribió: Great plot :) I've a dump of the SPI transfers during a night taken with the logic analyzer... but have found no time yet to process the dump to extract the transfers. Of course it is easier to take it from the serial port data :) The adjustment looks quite closely related to the temperature. Regards, Javier El 02/02/2012 06:15, Scott Newell escribió: Javier Herrero's exciting DDS discovery led to this plot of the unit tweaking the frequency (cmd 0x22): http://n5tnl.com/time/fe-5680a/graphs/dds_autotuning.png It appears to make an adjustment even before lock! ___ 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. -- Javier Herrero Chief Technology Officer EMAIL: jherr...@hvsistemas.com HV Sistemas S.L. PHONE: +34 949 336 806 Los Charcones, 17 FAX: +34 949 336 792 19170 El Casar - Guadalajara - Spain WEB: http://www.hvsistemas.com ___ 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.
Re: [time-nuts] FE5680 DDS plot
At 03:20 AM 2/2/2012, Javier Herrero wrote: I forgot... have you had the opportunity to check if the difference between the two DDS programming words is the same in all cases? All my readings leds to 1400.00x Hz, I've not looked at it but probably the difference in DDS counts is constant. So far, it's been a constant 1400.001347 Hz. But I've not dialed in a range of offsets yet. According to cmd 0x22, my non-locking unit appears to startup with the DDS at 2.527819 and 18.755189 MHz. (!) -- newell N5TNL ___ 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] FE5680 DDS plot
Javier Herrero's exciting DDS discovery led to this plot of the unit tweaking the frequency (cmd 0x22): http://n5tnl.com/time/fe-5680a/graphs/dds_autotuning.png It appears to make an adjustment even before lock! -- newell N5TNL ___ 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.
