How are you powerting the board?
USB or DC?
If DC, is the power supply a switcher?
What is the processor frrequency you are running at?
If you hold the reset button down, what happens to the level?
What all is connected to the board?
How are you measuring the 144MHZ?
Gerald
Thx for your reply but I think that all interference comes from poor grounding on my breadboard and all the long cables.
I’ll give it a new try when I get the components for my CoolRunner-II cape. It is S9+++ om my ham radio 
Best,
Andreas
2012/9/10 Gerald Coley <gerald@beagleboard.org>
Understood!
Gerald
So, which pins did I not connect?
Gerald
I did not design the board for ultra low noise environments. It is designed to be sold as a $45 board. If you are working in this type of an application, my expectation would be that this would have been obvious, but maybe not.
You could design a cape that terminates the unused pins and adds a connector with a ground pair. The use whatever connections you need. You could then also put it in a shielded case.
Gerald