Thanks,
I did manage to sample two real channels at 25 MHz! I set the NCO to 0 and the mux to "A:AB". I don't know why I didn't think of this trick earlier.
Now the real part is channel 0 and and imaginary part channel 1. I will next try to do the fpga mod. Can you point me to the correct file in the fpga? I'd like to take a stab at this.
The reason why I'm doing this, is I'm exploring the possibility of using the N200 as a phase comparator. We are looking for picosecond scale phase variations, and I'm trying to do all the calculations in double precision floating point to avoid phase inaccuracies caused by integer arithmetic.
juha