If you check on ebay you will find a large number of sellers offering a AD9850 Module similar to the one shown in the photo to the left.
My guess is that this is a liquidation due to a design build error, since they are being sold for a price of about 1/2 the price of the DDS chip alone. The modules are assembled and tested. The design error I noticed is that the wrong output filter is used. These boards use the 9850 running at 125MHz. A 125MHz DDS should have a 50MHz LPF, but it seems that these modules have the 75MHz LPF the chip maker recommends for the AD9851 running at 180MHz. My guess is, someone just copied the wrong filter from the wrong data sheet, and it wasn't caught until they went into production.
But for amateur radio applications they work fine up to about 40MHz. You can push them to 50MHz by adding a correcting filter, which is included in my controller PCB, but the output level is low in the 40-50MHz range.
I have designed a controller board that allows ham to control two of
these modules with one controller. The modules (1 or 2) plug into the
controller mother board, and a standard LCD can be plugged into the
back, see picture below.
More views below:
When used with two DDS Modules, as shown above. One can have separate frequencies in each modules, or they can be the same frequency, but 90 degrees out of phase (i.e. Real and Imaginary data, or in-phase and quadrature data) to do so one must lock the two 125 MHZ clocks together by removing one clock can, and jumpering over the clock from the other unit. This method is described in the Analog devices data sheet for the AD9851 (figure 7 on page 11)
Above: Schematic of DDS Module, has some errors
Below: Schematic of My Controller/Motherboard, preliminary may have
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