Hi That's what I used to do for the FMT stuff. I just used a simple divider to get a 1 KHz tone.
Bob On Mar 22, 2011, at 9:12 PM, paul swed wrote: > Thanks Bob > > On Tue, Mar 22, 2011 at 9:09 PM, Bob Camp <[email protected]> wrote: > >> Hi >> >> If you have a stereo sound card, you could digitize both the synthesizer >> output and the BFO. Mix them both down digitally. Do the angle conversion >> and compare the phase records. The sound card clock should pretty much drop >> out that way. >> >> Bob >> >> On Mar 22, 2011, at 9:05 PM, paul swed 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. >> >> >> _______________________________________________ >> 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.
