Hi Jack, Do have a look at Dave WB6HDW's fine DDS SDR and filter kits. I see he already posted a reply to you. If you want general coverage, then you want to use a DDS (see detail below). Plus, you need to use differential amplifiers on the QSD output instead of op-amps to reduce the affect of antenna impedance changes. A purist might also want to put a preamplifier/preselector on the front end of the radio to further isolate the affects of changing antenna impedance on performance. But many will argue that a preamp is not necessary and may actually be harmful as the dynamic range of the QSD is compromised. I don't believe the WB6HDW SDR has a preamp, but I think it does use differential amplifiers.
Using DDS for the VFO is optimal at the moment. Yes there are spurs, but the phase noise is good and you can tune them as often as you want without worrying about wearing out limited flash memory in parts like the Si570 which is so popular with the Softrock SDR's. Perhaps this flash memory issue is one reason why the designer of the Elektor board compromised with the Cypress Semi part. I think the CY27EE16ZE part used in the Elektor board may have a volatile (non-flash) register for tuning. The part I'm testing now, the CY22393 is, as suspected, seemingly rather pretty poor in the area of phase noise performance. And, it has no non-flash register to tune with either. There are five selectable non-volatile registers for only one of the three PLL's in the CY22393, the remaining two have only one dedicated register. This would allow for a "5-band" SDR without having to start writing to the flash memory again. Maybe 7 bands if you tie together the remaining two PLLs, each PLL can be individually enabled or disabled. Best Regards, 73's David --- In [email protected], "artus1947" <[EMAIL PROTECTED]> wrote: > > David, > > Thanks for the information. The Elector seems like a poor path for > me to follow. I will look into the other group but will continue my > quest for a more general coverage SDR. I am using an RXTX6.2 and > really enjoy the aspects of SDR. > > 73, > > Jack > --- In [email protected], "drmail377" <drmail377@> wrote: > > > > 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.yahoo.com/group/G8JCFSDR/ > > > > 73's David (WB4ONA) > > > > --- In [email protected], "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) > > > > > >
