Ray Yeap, like I said, in not too few words, it is sort of an idea. Experimental. I am seeing that the suppression of the LO IN, which then is modulated by the signal from the antenna, will unsuppress the LO IN and mix with it. And the spur I think would have to mix with something coming in on its frequency to appear in the display. Which is theoretical too and uncertain. It might be seen though even suppressed. But this may never work in any degree also.
It seems to me at the momement that it is possible to modulate the spur as I mentioned. But it still is going to be a spur. I am hoping it however might be possible to get the modulation to be heard over the spur better. So it is not an elimination of the spur but hopefully a dB wise increase of the modulation over the spur. 6 dB might be enough to bring up the modulation loudness if that can be obtained? Spurs that are wider in nature than those that look like single cw tones are more like what I think might be modulated over top of. Single tone like spurs (spike like or cw like tones) these I would think would act like single tones and intermodulate and be heard as a cw tone. Hence remain like a cw carrier in the spectrum and not be effected by this idea. So those sorts of spurs would remain no matter what. Anything CW like will be passed and has to be passed for use on CW. Such tones can not be eliminated. Dan --- In [email protected], "WB6TPU" <[EMAIL PROTECTED]> wrote: > > Dan- > > When they discuss the 'suppression' of spurious responses with the > Gilbert cell mixer topology I'm fairly certain they are referring to > the reduction of LO radiation out of the antenna port due to the > balanced nature of the mixer. > > DDS spurs are an entirely different topic and are primarily generated > due to the following mechanisms: clock spur feedthru, numerical > truncation errors in the phase accumulator, angle to amplitude mapping > errors and imperfections in the DAC. Over the past 5 years or so > things have improved by leaps and bounds as evidenced by some of the > latest offerings from Analog Devices as compared to earlier generation > devices. While I never say never, I don't think that balanced mixers, > Gilbert Cell or otherwise, are going to do much to reduce DDS spurs. > > Just my 2 cents worth.(I'd really like to be proved wrong). > > > -Ray WB6TPU > > > > > --- In [email protected], "Daniel Jackson" <wavelengths@> > wrote: > > ... > ... > ... > > So it has a double balanced mixer. > > > > But.... > > > > "...prevents the influence of spurious radiation..." Maybe we can > > learn and borrow something from this idea for the suppression of > > spurious radiation? > > > > Let me take a crack at how I think we might be able to use a balanced > > mixer to rid us of some of them pesky DDS spurs. > > > > ... > ... > .... >
