"Hi Nick,
I'm getting similar reading variations from the 2 DIY Drone HMC5843 REV1.1 boards I purchased in NOV 2010.
Below is the response from Chris Anderson followed by my e-mail to him after seeing his response to your posting here.
I purchased 2 of the new DIY Drones Rev 1.1HMC5843 boards back in late NOV.The data I'm get from them seems to have way too much "jitter". With the magnetometers stationary and flat and level:unit 1's readings vary by 54 count in X, 57 counts in…