Sorry Dave, I missed the "Direct" conversion in your post. You mean direct A/D without QSD like Phil Covington's Quicksilver QS1R. That's a bit over my head at the moment. Right now I'm looking at a GPS stabilized DDS and bypassing the sound card using ADC/DAC's with a QSD. Direct method may be the next project.
--- In [email protected], "drmail377" <[EMAIL PROTECTED]> wrote: > > Hi Dave, > > Sorry for the late reply... Yes, I address the ADC/DAC from/to PC via > USB interfacing: > > http://groups.yahoo.com/group/soft_radio/message/3336 > > I'm just starting to look into the application software part of it though. > > Thanks, David > > --- In [email protected], "Dave Wade" <g4ugm@> wrote: > > > > David, > > > > If you are a real purist why not sample at RF? I know the cost is > about 4x > > the cost of the Elektor kit but the result must be worth it. When I > looked > > at recent reviews in RadCom the direct sampling boards came out > realy well. > > > > Dave > > > > > > > > -----Original Message----- > > From: [email protected] [mailto:[EMAIL PROTECTED] On > > Behalf Of drmail377 > > Sent: 03 April 2008 16:47 > > To: [email protected] > > Subject: [soft_radio] Re: Elector Boards > > > > > > > > > > Hi Dave G4UGM, > > > > OK, this is top-down typing, please correct any obvious (and likely) > > glaring mistakes. I'm short on time... > > > > You raise excellent questions. You are right, theoretically the divide > > by 4 for the quadrature LO will reduce phase noise by 20*log(4) or 12 > > dB, but not really. Even at room temperature, and depending on the > > sequential quad-divide part thresholds, power supply noise, etc, we > > might want to at-least halve that. I'm looking into this further, > > especially considering the Silicon Labs Si570 20ppm LVDS part and > > Si571 voltage controlled ref input part (wrap the 571 around another > > PLL loop that is GPS disciplined perhaps?) > > > > Let's stick with 12 dB for now. I feel -135dBc/Hz at 10kHz is > > reasonable for a relatively high performance HF VFO. Let's work back > > from the example extrapolated from the Elektor's jitter to PN in my > > previous post assuming a -20 db difference from 1kHz to 10kHz, the > > center of interest for a 24 kHz BW. -135-12-20=-103 dBc/Hz at 1kHz, > > 18dB better than the extrapolated Elektor PN from the Cypress jitter > spec. > > > > Granted, there is a lot of "slop" in this analysis, but one might > > argue that an error margin of 20dB is not likely methinks. Also, the > > Cypress part may preform better at certain "select" frequencies and > > lower frequencies as well (Cypress doesn't disclose), yes it is a PLL > > device, and as such can trade close-in vs. outer "hump" phase noise > > performance vs. loop BW. But we're interested in close-in performance > > for HF reception. > > > > BTW my Peppermint "replacement" for the "Blueberry" now seemingly > > discontinued demo board for the device used in the Elektor LO is not > > performing anywhere near these numbers. A different animal entirely > > and seemingly no non EEPROM register to write to in order to set the > > frequency (EEPROM wear-out problem). > > > > But I am feeling better about the Elektor board after you raised these > > questions Dave. Given that the Si570/671 from Silicon Labs wasn't > > available at the time the Elektor board was designed, the Cypress part > > may have been the best choice. > > > > I'm sure the Elektor board is doing fine by most if not all users. > > However, I'm somewhat of a purist and the options for parts are > > changing rapidly. I just wish the Elektor board was more affordable. > > I'm a victim of the declining USD. > > > > 73''s David > > > > --- In [EMAIL PROTECTED] <mailto:soft_radio%40yahoogroups.com> > ups.com, > > "Dave Wade" <g4ugm@> wrote: > > > > > > 1) Whats the phase jitter on a typical PC sound card? > > > > > > 2) Doesn't the divide by 4 reduce jitter. The chip is not used to > > > generate the IQ directly . > > > > > > 3) The ready built price to the UK is only marginally more > > than I can > > > buy the bits for. I can't find a ready built general coverage board in > > > Europe for anything like the price. > > > > > > > > > > > > -----Original Message----- > > > From: [EMAIL PROTECTED] <mailto:soft_radio%40yahoogroups.com> > ups.com > > [mailto:[EMAIL PROTECTED] <mailto:soft_radio%40yahoogroups.com> > ups.com] > > On > > > Behalf Of drmail377 > > > Sent: 28 March 2008 04:53 > > > To: [EMAIL PROTECTED] <mailto:soft_radio%40yahoogroups.com> ups.com > > > Subject: [soft_radio] Re: Elector Boards > > > > > > > > > > > > Hi Jack, > > > > > > You might want to rethink building that Elektor board, at least the > > > way it is "out of the box". I took a good look at it and found that it > > > uses a Cypress Semiconductor CY27EE16 PLL Clock Generator as a > > > synthesized local oscillator. The CY27EE16 has a typical jitter > > > specification of 250ps rms. This is pretty bad. By comparison, a good > > > crystal oscillator should present less than 1ps rms jitter. To give > > > you an idea how this translates to phase noise: > > > > > > 0.4psrms jitter (Isotemp OCXO134-10 10MHz VC-OCXO): > > > 10Hz = -105 dBc/Hz > > > 100Hz = -125 dBc/Hz > > > 1000Hz = -140 dBc/Hz > > > > > > 230psrms jitter (for comparison): > > > 10Hz = -50 dBc/Hz > > > 100Hz = -70 dBc/Hz > > > 1000Hz = -85 dBc/Hz > > > > > > Not only that, I get the feeling that the CY27EE16ZE may be set for > > > deprecation. At least the Blueberry demo board for the part has been > > > discontinued and replaced with a Peppermint demo board. The Peppermint > > > demo board uses a CY22393 three PLL clock synthesizer part. The > > > CY22393 has even worse specified jitter, a whopping 400psrms! But > > > there are allusions in the data sheet that the jitter may be > > > significantly less for some "settings", but it doesn't elaborate. I've > > > just received a couple of Peppermint boards to test. > > > > > > Anyway, the seemingly poor choice of L.O. on the Elektor radio, along > > > with the outrageously high price put me off. If you do build one of > > > these, you might want to replace the CY27EE16ZE with an Si570. The > > > Si570's jitter is specified at around 0.35psrms. Mike, KF4BQ has > > > measured the phase noise of the CMOS version of Si570 to be -130dBc/Hz > > > at 3-7kHz offset. His report is in the Files section. > > > > > > If you do replace the CY27EE16ZE with an Si570 (or something else), > > > remember the G8JCF SDR software that accompanies the Elektor radio > > > most likely will not be able to control the L.O. frequency. There's a > > > group here for the G8JCF software with some discussion on the Elektor > > > board as well - but not a lot of activity: > > > > > > http://groups. <http://groups. > <http://groups.yahoo.com/group/G8JCFSDR/> > > yahoo.com/group/G8JCFSDR/> > > > yahoo.com/group/G8JCFSDR/ > > > > > > 73's David (WB4ONA) > > > > > > --- In [EMAIL PROTECTED] <mailto:soft_radio%40yahoogroups.com> > > ups.com, > > > "artus1947" <artus@> wrote: > > > > > > > > Hi folks, > > > > > > > > I wonder if anyone knows of any other sources for the Elector > > Boards -- > > > > the shipping to the States (25 euros) is horrible. I tried etching > > the > > > > boards myself, but I can't get a good registration between layers. > > > > Thanks. > > > > > > > > 73, > > > > Jack (W0FNQ) > > > > > > > > > >
