4Mbps hack wiring & 48 MHz spurs

Just fyi, here's how I did the 4msps wiring hack : http://i.imgur.com/TODkU.png Basically use resistors (I used 270R which is a bit high ,between 20 and 10R would bwe better) on the back side on the PCB. I initially started with wire jumpers on the pins, then moved to resisors on the top but that created a huge loop area with the ground return (there is no gnd on those connection) which was heavily radiating. Mounting on the back like that dropped it significantely for me (especially on baseband), but you still clearly see it. I think the FPGA drive strength on the data pins is still way too high and should be reduced. Maybe using spread spectrum on the MCI would be another idea ? Cheers, Sylvain