If the software implements acquisition of cross power spectra Then one could implement a near state of the art cross correlation PN test set based on this. With a suitable preamp the sound card could also be used for power supply and reference noise measurement.
Bruce On Thursday, March 24, 2016 04:54:47 PM Bob Camp wrote: > Hi > > The board is pretty non-critical. It’s 90% audio. The biggest hassle is a > power supply. You would *like* a fairly high voltage, at least if you are > driving a spectrum analyzer. That may not be quite the case with a sound > card. It depends a *lot* which one you are running. Something like a QA401: > > https://www.quantasylum.com/content/Products/QA401.aspx > > Would make a good target device. It’s based on the AKM 5397 So might some > Janus boards. They are based on the earlier(?) AKM 5394. The QA401 has the > advantage of a nice box and full USB isolation (ground loops are a pain). > It also has drivers and all the OS hooks. The Janus is a bit more “DIY” > with no drivers or interface (let alone isolation). The Janus is < 1/4 the > price. > > The high voltage (+/- 18V linear regulated) supply approach makes a lot of > sense with the QA401. It probably does not make as much sense with the > Janus. Switching regulators of any sort are something I would strongly > recommend against in a system like this that is trying to measure noise > floor at audio …. > > The schematic changes a bit depending on what the target is. I can draw it > up if there is a consensus on the target. One example: If the “sound card” > is DC coupled, you can use it to indicate (and check) quadrature. If it’s > an AC device, you need some sort of isolated output for another indicator. > > Bob > > > On Mar 24, 2016, at 1:31 PM, John Ackermann N8UR <[email protected]> wrote: > > > > I'd be willing to assist with board layout if someone wanted to make this > > into a real project (e.g., fully developed schematic). TAPR might be > > talked into supplying at least bare boards; we'd have to get a sense of > > demand before committing to a full kit or assembled unit. > > > > John > > ---- > > > > On 3/24/2016 9:04 AM, jimlux wrote: > >> More like $40 in parts, without a board, etc. > >> The RPD-1 is $20.70 > >> LT1678/LT1679 is a nice low noise opamp that does rail to rail and is > >> about $5 > >> etc > >> > >> On 3/24/16 4:42 AM, Bob Camp wrote: > >>> Hi > >>> > >>> Pretty simple: > >>> > >>> Double balanced mixer, RPD-1 is one option, there are others. > >>> > >>> Fairly simple L/C lowpass between the mixer and an op-amp. > >>> > >>> 20 db positive (non-inverting) op-amp amplifier string after the mixer > >>> > >>> Output of the string goes to the sound card. Use a good (dual / quad) > >>> audio op amp > >>> > >>> Quadrature amp picks off the output of the first op amp stage, switch > >>> and resistors to set gain, pot to set op point. > >>> > >>> ==== > >>> > >>> So what you have is an old style quadrature phase noise amp and “PLL”. > >>> More or less a very junior version > >>> of the 3048 test box. Like any setup of this sort, you check two > >>> similar oscillators. They run in quadrature and > >>> you do a few “measure this with switch in position A” sort of things > >>> to set things up each time. > >>> > >>> Nothing exotic. > >>> > >>> Bob > >>> > >>>> Any documentation on this $40 phase noise test set? > >>>> > >>>> Rick N6RK > >> > >> _______________________________________________ > >> 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.
