Hi Ok, A bit more info:
1) Quadrature PLL using an RPD-1 DBM and a home brew lock box. 2) Willingness to accept that I'm measuring a pair of oscillators 3) Plenty of sources at the appropriate frequencies 4) First took a shot at this in 1975 (I forget the Fluke app note number ...) been doing it ever since 5) Appropriate preamp between the RPD and sound card is a work in progress 6) Sound card is a 192 KHz / 24 bit / ~110 db snr class card 7) Sound card will get butchered for the application. 8) Should be able to hit -165 ish floor, -120 ish at 1 Hz Except for the 16 bit limitation, Baudline looks like it's got what I need. Bob On Feb 18, 2010, at 7:53 PM, John Miles wrote: > Unfortunately there's no way to build a sound-card application that can > measure phase noise in the general case without a lot of additional > hardware. Baseband PN analysis with an FFT presupposes that you have some > external means of downconverting the DUT signal to DC with a superior > reference at the same frequency, tuned with a quadrature PLL. There must be > a suitable high-pass filter and LNA to block any DC residuals and preamplify > the remaining part of the noise sideband. > > Further, it's often the case that noise close to the carrier is strong > enough to keep you from being able to use enough gain to see the broadband > floor, so you actually need more than one high-pass filter ahead of the > sound card in many cases. These switchable filters were mandatory with the > old 13-bit signal analyzers like the 3561A, and may still be needed today if > you want to look down to 1 Hz. If you restrict your offset range to (say) > 100 Hz to 20 kHz and require a 24-bit sound card, you can probably get away > without the switchable HPFs. > > It'd be helpful to know exactly what sorts of measurements you need to make, > and on what devices. PN measurement is a *lot* of work, on both the > software and hardware sides. Much of it goes into developing a suitable > calibration process. Take a look at the 3048A manuals sometime, realizing > that the 3048A hardware itself is not very complicated... > > -- john, KE5FX > >> -----Original Message----- >> From: [email protected] [mailto:[email protected]]on >> Behalf Of Bob Camp >> Sent: Thursday, February 18, 2010 4:18 PM >> To: Discussion of precise time and frequency measurement >> Subject: Re: [time-nuts] Sound Card Spectrum Analyzer >> >> >> Hi >> >> Both are very cool programs. Both are full of all sorts of neat >> features. As far as I can see, neither one has the features I'm after. >> >> More or less - I want it to run like a clunky HP audio analyzer >> rather than a very cool tool for ham radio. >> >> Bob >> >> On Feb 18, 2010, at 6:33 PM, Don Latham wrote: >> >>> You have looked at: >>> spectran and spectrum lab ? >>> Don >>> >>> Bob Camp >>>> Hi >>>> >>>> Assuming I have a decent sound card, and a computer, the next >> thing I need >>>> is software. If I want: >>>> >>>> Required: >>>> >>>> 1) non- commercial >>>> 2) 1 Hz normalization >>>> 3) good low frequency processing (decimation ahead of the fft) >>>> 4) low cost >>>> >>>> Much preferred: >>>> >>>> 5) a non-evil OS >>>> 6) Rational performance on a non-quad core system >>>> 7) free >>>> 8) rational calibration >>>> 9) scope view. >>>> 10) reasonable graphics >>>> 11) active support by the author >>>> >>>> The application is measuring phase noise. That what makes 2 & >> 3 pop up on >>>> the list. >>>> >>>> I've looked at a lot of programs and they all seem to be >> pretty slick. The >>>> ones I've looked at so far don't quite hit the mark for phase >> noise. I'm >>>> pretty sure that there are others on the list who have dug >> into this same >>>> issue already. >>>> >>>> Bob >>>> _______________________________________________ >>>> 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. >>>> >>> >>> >>> -- >>> Dr. Don Latham AJ7LL >>> Six Mile Systems LLP >>> 17850 Six Mile Road >>> POB 134 >>> Huson, MT, 59846 >>> VOX 406-626-4304 >>> www.lightningforensics.com >>> www.sixmilesystems.com >>> >>> >>> _______________________________________________ >>> 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.
