Miura, I have a few questions. 1) how do you establish and maintain quadrature offset in phase between the two DDS chips? 2) are you aware that the "square wave" outputs have a much higher phase jitter than you would get by using a compatitor on the sine or triangluar outputs?
Cash Olsen KD5SSJ Kits to build Scotty's Spectrum Analyzer http://www.zianet.com/erg Scotty's Spectrum Analyzer website http://www.cpu-net.com/host/wsprowls Sam Wetterlin's website http://www.wetterlin.org/sam/ Yahoo Builders Group http://groups.yahoo.com/group/spectrumanalyzer/ -----Original Message----- From: soft_radio@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Miura Kazunori Sent: Saturday, February 09, 2008 5:04 AM To: soft_radio@yahoogroups.com Subject: Re: [soft_radio] Oscillator, why divide/4 Hello It is important for QSD/QSE to keep a phase difference of 90 degrees precisely.I made various phase shifter, CR and johnson counter,ICS672. But it is difficult to get correct phase shift for reject image signal. I am making quadrature DDS signal generator. http://www.eleki-jack.com/lab/9834x2.html If this quadrature DDS signal generator is good result, I will report here. JA7TDO Dave Wade ????????: > > > Why don't you go and have a look on Google, I stuck in "SDR For the > Masses" and got loads of hits. Very interesting info on how and why > things fit together the way they do. > > Having read these I was wondering why these folks use the "divide/4" > approach when there are now DDS chips available very cheaply, that > provide I/Q outputs like the AD9851. I am building the Elektor SDR > > http://www.elektor.com/magazines/2007/may/software-defined-radio.91527 > .lynkx > <http://www.elektor.com/magazines/2007/may/software-defined-radio.91527.lynk x> > > which uses the Cypress cy27ee16 and then a divide/4, and as an amateur > getting one of those was a complete pain. Wouldn't the AD9851 have been > a better choice, and as an amateur I can get samples of those free of > charge? > > Dave G4UGM > Illegitimi Non Carborundum > > > > ----- Original Message ----- > *From:* Adnan Yusuf <mailto:[EMAIL PROTECTED]> > *To:* soft_radio@yahoogroups.com <mailto:soft_radio@yahoogroups.com> > *Sent:* Saturday, February 09, 2008 6:26 AM > *Subject:* [soft_radio] Oscillator, what kind? > > Hi, > What kind of oscillator is used in the designs like SDR for the Masses > project? Do we use a clock oscillator or just any sine wave > oscillator? > > yours truly, > adnan yusuf > > Yahoo! Groups Links No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.5.516 / Virus Database: 269.19.21/1266 - Release Date: 2/8/2008 10:06 AM No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.5.516 / Virus Database: 269.20.0/1268 - Release Date: 2/9/2008 11:54 AM
