By looking at AD9850 DDS or other similar parts made by Analog Devices Company it is obvious that the output signal amplitude changes by frequency. This can be shown as x= pi* fout / fClock and amplitude changes by Sin[x]/x. By using this formula we should see an amplitude drop less that 20% between 1Hz to 50 MHz but this is not the case that happens. As I am driving this part, I see the amplitude is around 1 volt pk-pk at 10Hz and 10mV at 50 MHz. Is anything I am missing in these calculations?