[hpsdr] PA3AKE Project update - DDS

[Giancarlo Moda]

Hi all,

I have tried to send the following message to the list but had error messages. Some of you may have seen this information in other groups.

I have been talking to Colin Horrabin, G3SBI, and we spoke about the good work Meirtein Bakker, PA3AKE, is doing on his high performance analog front-end receiver using the H-Mode Mixer. 
Martein is a very good research engineer and amateur radio. With his knowledge, determination and attention, using homemade test equipment and a W&G spectrum analyzer he has identified a design problem in the AD9910 which will probably also affect the AD9912 and other recent DDS chips by ADI. Colin was able to talk to Analog Device high speed DDS group in North Carolina. There was a great deal of reluctance to accept Martein's findings. Eventually they were able to duplicate his results and they were very grateful to Martein because the same mistake will not be made in their new designs. We have a very low phase noise with ADI 9910-12 DDS but we are discovering AM noise !!!! a problem not present with the AD9951.
As Colin stated, the remarkable thing is that it has taken an amateur radio state of the art receiver project to identify this and it has not been found by Analog Devices big customers with all their high tech test equipment. 
The bad news is that it is unlikely there will be a chip revision, even though the fix is simple unless there is pressure from a major customer. Maybe this is a good pressure some of our colleagues could apply to ADI from their engineering key positions.
Analog Devices is a company we all have a lot of respect for. The high speed DDS chips are a major technical achievement and are useful to our hobby as Martein will show. During chip development the design team probably paid too much attention to results from their high tech measuring equipment when by design it rejected a device parameter they should also have been looking for.
Martein has just published an update to report on the evaluation of the AD9910 DDS chip to be used as the DDS-Local Oscillator that complements the Down Conversion Frontend. The research regarding the AD9910 and especially its noise characteristics is finished. Those interested can visit his web page:

http://www.xs4all.nl/~martein/pa3ake/hmode/index.html

73 and with the occasion Season’s Greetings

Gian
I7SWX