I believe you will have band edge to edge issues only with the softrocks that use a phase shift network. Using a srv5 and a 9851 dds I have to recalibrate if I change the frequency significantly. Using a srv6 and the same DDS I don't. Using a circuit based on the Software Defined Radio for the Masses Pt 4 article, I can go to any frequency and not recalibrate. Using Winrad with the calibration set to 0, I can tune in an extremely strong sw broadcast station 10 khz up and cannot detect the image 10 khz down. Barry KK4VT
--- In [email protected], "n3hkn" <[EMAIL PROTECTED]> wrote: > > Since the DDS is only used as a clock source the spurious stuff I > see may be due to some other mixing events within the "system". I > have powered the DDS and the SoftRock V5 from separate gel cells so > the power source is not an issue. I have not seen any improvement > with clamp-on ferrites on the power, antenna, and the 12 inches of > RG-174 feeding the DDS to the V5. Most of the spurious stuff is > 10db, or less, above my noise level. Thus stronger signals come > through quite well and I can enjoy the good fidelity of the DC > receiver when listening to some of the shortwave broadcasts. For Ham > use the presence of low level spurs makes tuning across a band > looking for a weak signal very difficult. > > From all of the comments I have seen on DDS's as VFO's the 10bit DAC > is probably producing the best I can expect. With the need for a > tracking/adaptive wide-band phase/amplitude suppression system the > xtal based IF application, or a 96khz band slice, may be best. Now, > I did have an SDR-1000 and I admit that I never did any real tests > Ham band edge to edge on image rejection. So, how does the SDR-1000 > fare in maintaining Ham band image rejection balance with only 1 > phase/amplitude setting???? > > Dick N3HKN > > > > > --- In [email protected], "wavelengths@" > <wavelengths@> wrote: > > > > Dick N3HKN: > > > > There is that question about the square wave verses the sine > wave. The idea of using the DDS sort of board for the lower i.f. in > a receiver makes sense in light of the spurious reponce you > mentioned. In a narrower i.f. portion of the chain where the > extended band is cut off some. > > > > Someone was telling me that the Soft Rock 40 circuit however may > prove to be ideal in the long run, I am wondering how a sine wave > will operate in broadbanded terms to 96 Khz? I seem to think the > later would be more ideal in getting rid of spurs. I guess there is > no ideal circuit from all of the discussion going on so far. > > > > Time will tell more as more ideas are built and tested. > > > > Dan > > > > > > > _____________________________________________________________________ > > Call Anyone, Anytime, Anywhere in the World - FREE! > > Free Internet calling from NetZero Voice > > Visit http://www.netzerovoice.com today! > > > Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/soft_radio/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
