Hi It's certainly got all the blocks you would need to do the processing. Linking it to a decent interface looks like a bit of a chore. I plead "LAZY" when it comes to doing this from scratch.
I keep thinking there's got to be something out there that does all this .... Bob On Feb 18, 2010, at 8:27 PM, John Ackermann N8UR wrote: > You could also consider whether Gnuradio (http://www.gnuradio.org) could do > what you need. It has interfaces to the Linux sound system. > > John > ---- > > Bob Camp said the following on 02/18/2010 08:10 PM: >> 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. > > _______________________________________________ > 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.
