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.
