This has come up before, I found an “old reflector” article from 2011. But seeing the article referenced below made me think this was worth repeating as it’s probably an issue that needs pointing out every so often.
I’ve been using Silva compasses for almost 40 years and never saw this problem until the last few years.
In the last 3 or 4 years I’ve now had 3 different Silva Type 4 compasses have issues with complete or partial polarity reverses.
The article specifically mentions.
- Speaker magnets in Mobile phones
- Speaker magnets in Hand Mics on radios
- Magnets on rucksacks, for instance on Osprey bags which have drinks tubes and magnetic holders on the chest straps.
I suspect my own personal issues have been caused by storing amateur radio kit in the lid of my rucksack, next to my compass.