Oooops 3 more decimal places to the right. On Tue, Mar 22, 2011 at 9:05 PM, paul swed <[email protected]> wrote:
> Welll I sort of went past this and have a reasonable answer. > All system locked to a rb ref. > A HP8660 as source gen and set to 3 MC. > The 3586 if is 15.625KC. > Set a HP 3335 to the IF frequency and on a scope the signals lined right up > and are stable. Bob I think you or someone else mentioned this fact and I > verified it. > > Then I went to the audio out on the 3586. That signal should be 1.850KC. > Set the 3335 to 1.85 KC and watched the drift rate for USB and LSB. > The answer is for 1 cycle drift rate is; > 2.68 seconds for lsb or 2.0X10-4 (This will bring responses) > 9.97 seconds for usb or 5.4X10-5 > > Have to say that drift is way below what my ears can hear these days. > So though I could change the DDS for FMT use and drive the decimal point at > least 3 more digits to the left. I really have to say good enough and a > success from just two weeks ago. > > Regards > Paul > WB8TSL > > > On Tue, Mar 22, 2011 at 8:45 PM, Bob Camp <[email protected]> wrote: > >> Hi >> >> My assumption is that to do any of this, some sort of calibrated clock on >> the sound card would be needed. Either a mod to the card, or some luck with >> the built in clock source. It's going to be needed weather you use an FFT or >> some other DSP process. For a "fully locked" system, mod the sound card for >> an external clock and whip up a phase locked loop to drive it. >> >> The mix down source would likely be purely digital. Inserted after you had >> the sample stream. My first choice would be to use a 2 KHz "stupid clock" (0 >> 1 0 -1) with an 8 KHz sample rate. Pretty simple math. >> >> Bob >> >> >> On Mar 22, 2011, at 6:23 PM, Alberto di Bene wrote: >> >> > On 3/22/2011 5:24 PM, Bob Camp wrote: >> >> The other approach would be to simply take the samples, do a mix down, >> and >> >> get the phase from an ATAN calculation on the I/Q results. That would >> give >> >> you pure phase and thus frequency. >> > How do you intend to generate the numeric LO stream to use for the mix >> down ? It must have a sampling rate >> > with a precision comparable to what you intend to measure... >> > >> > 73 Alberto I2PHD >> > >> > >> > _______________________________________________ >> > 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. >> > > _______________________________________________ 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.
