Hi Janne, Building a DDS with AD9951/4 is easier than you think. I had copied the design by DL5MGD and it was pretty easy and it works fine even though I used only a 400 MHz clock (80 x5). His web page is: http://www.dl5mgd.de/dds/AD9951.htm , since it was so easy I built two of them, one for use as a standalone/LPT control SG, the other is part of a Vector Network Analyzer designed by IW3HEV, I simply replaced the AD9851 with an 9951. I would give the I0CG 500 MHz clock a try when I have more free time. I used the DDS SG currently for my SDR setup, it works pretty good although I did notice some birdies.
73 de D.J. Wang / NM3R ----- Original Message ---- From: iami78 <[EMAIL PROTECTED]> To: [email protected] Sent: Tuesday, March 13, 2007 3:14:47 AM Subject: [soft_radio] Re: Single AD9954 with counter or dual AD9954 to form IQ VFO. > Hello Janne, > > welcome to the group which, I am sure, will benefit from any >contribution you will give. > >The AD9954 should have the same core of the AD9951. This latter has >been used by Giuliano I0CG in his SDR-X receiver, with a clock of 500 >MHz. The SDR-X can receive up to the 6m band, so the DDS must be able >to generate at least up to 51 * 4 = 204 MHz, and actually it is. >At that frequency there are much more spurs than at lower >frequencies, >but in any case the spurs level is lower than in the much celebrated >SDR-1000. >Giuliano told me that it tested the AD9951 even at 600 MHz clock >frequency, and it continued to work, though it is spec'ed only up to >400 MHz. > >Good luck with your project. > >73 Alberto I2PHD > Hi Alberto! Thanks for the reply. So, it would be possible then. It might be wise to make pcb with just one AD9954 and test it with, lets say 550 MHz clock signal. If it doesn't work well enough, just put another PCB back to back and make it IQ pair. The thing is, that here in Finland 6 meters go as high as 51.990, which is the output section for repeaters. So, I need 208 MHz to cover that up. Best choise of course would be to use pair of AD9954, but I'm a bit afraid of the complexity, because I haven't done anything with DDS before. Also the synchronization, 90 degree phase shift for a first DDS project, including the register stuff, sounds too complicated :-/ But I'm also afraid that going the easy way might bring as much problems, hihi. 73 de Janne, OH1GTF ____________________________________________________________________________________ Sucker-punch spam with award-winning protection. Try the free Yahoo! Mail Beta. http://advision.webevents.yahoo.com/mailbeta/features_spam.html [Non-text portions of this message have been removed]
