Hi,
thanks for all the replies. I have 2 planes (power and ground) and also like motorola adviced a seperate isle (using an inductor) for the PLL and a lot of decoupling capacitors. I have 2 SDRAMs.
@flatulent
I already did a measurement with our DSO (FFT capability) and an active probe with a short loop wire, formed to a ring, connected to it but I'm not sure if I do measure the radiated waves or only magnetic fields. I'm not very experieced with this, what do you think?
@wolf69
I've foreseen serial termniations for the most signals (and additionally parallel for the clocks) and did the pcb layer stackup accordingly (~50R impedancy), but which signal is the bad guy (-:
@GaAs FET
adding ferrites helps really to reduce the 50MHz emissions. I put it at the supply cable and everything was fine. But for all lines it's pretty expensive ... I'll do it if nothing else helps
@mr_ghz
good hint, I first thought it's the CPU/core current but it does not fit with the overtone. I'll concentrate on the SDRAMs.