[Leica] Rare hard disc problems

[lrzeitlin at gmail.com (Lawrence Zeitlin)]

Henning,
I grant that hard disc drives are safe against normally encountered magnetic
fields but in rare instances they can be influenced by external
electromagnetic fields. Years ago my firm was prime contractor on a highly
computerized weather reconnaissance system to be installed on a Boeing KC
135. While we were adjusting the system on the ground we noticed that it was
generating errors which seemed to increase over time. After a couple of
hours of operation it was producing nothing but garbage. It took hours of
head scratching analysis to find out that we were being periodically
illuminated by a radar being tested in an adjoining hanger. The radar pulses
were writing random bits into memory which accumulated over time. Even the
hard disc was affected if the pulses hit during a write cycle. The radar was
several hundred yards away and the computer was well shielded. The pulses
were entering through the peripheral and power cables. A laptop in a plastic
case a few feet from a radar antenna would be much more vulnerable. The
moral is "Don't put your laptop in front of a radar or in a microwave oven."
Larry Z