Hi Janne, I have built two boards, one with AD9951 and another with AD9954, since they have the same pinouts, I used an identical PCB design. The most difficult part is line up all 48 pins and solder them, there wasn't that many external parts to solder after that. I agree that using the internal multiplier is not a good idea as it generates a lot of spurious signals but I was just trying to get it working as quickly as I can. DL5MGD published the PIC hex code and a VB prgram so you can control it with an 16F877 or thru printer port. That make thing a lot easier. I would have to rewrite it if I change the reference clock frequecy and multiplication factor. Later, I did write some AD9951 control code when I get more familiar with teh DDS chips and modify IW3HEV's VNA program to drive my AD9954, it turns out it was not as difficult as I original thought. DL5MGD's design is pretty good and you certainly can improve the spurs by using an external 500-550 MHZ clock. I0CG's design uses a XTAL OSC at 100 MHz or so and filter out unwanted harmonis. Spur improvement probably depends on how clean the 100MHz osc you will be using. 73 de DJ/NM3R
----- Original Message ---- From: iami78 <[EMAIL PROTECTED]> To: [email protected] Sent: Tuesday, March 13, 2007 3:23:27 PM Subject: [soft_radio] Re: Single AD9954 with counter or dual AD9954 to form IQ VFO. --- In [EMAIL PROTECTED] ups.com, "D. J. Wang" <[EMAIL PROTECTED] > wrote: > > 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 Thanks for the reply Wang! Yeah, it shouldn't be too hard! I've actually visited dl5mgd's sites before, but now I understood it much better :) I just started to draw circuit board with Eagle. I have the old version 4.01 and just noticed that it doesn't have TQFP 48 on the library and couldn't find it from the internet, so I had to make it manually, pheeewww. Just a question about your reply. Did you mean with "Building a DDS with AD9951/4 is easier..." same as "Building a DDS with AD9951 / AD9954 is easier..." or "Building a DDS with AD9951 frq/4 is easier...". Is it acceptable to use the multiplication of the clock frequency? I've heard that it may result some phase noise problems? It would be quite easy to use just the same multiply -method like you, instead of building direct 400..500MHz oscillator. Reading the AD9954 datasheet about 20 times gives somekind of idea how to access the AD9954 tuning words & stuff, but I think it might be much easier to study someone's earlier work. Maybe I should go with the dl5mgd's design? 73 de Janne, OH1GTF ____________________________________________________________________________________ 8:00? 8:25? 8:40? Find a flick in no time with the Yahoo! Search movie showtime shortcut. http://tools.search.yahoo.com/shortcuts/#news [Non-text portions of this message have been removed]
