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.
This hasn’t happened to me yet, but has to my Brother in law - mobile phone being the prime suspect.
It is perhaps more of a concern than ever, as many of us use a GPS device normally, and have the compass for backup. It may not be used for weeks, and then when you need it in poor visibility…
Probably a good idea to check it regularly, as well as keeping it away from magnets etc.
Curiously, I use mine most often to set a return bearing when I arrive on a summit. It is all too easy to go marching off in the wrong direction an hour or two later In this case where I only need a bearing relative to the summit, reverse polarity wouldn’t matter, unless it had reversed during the stay on the summit…
Well, its been three years since this topic was live. Maybe worth flagging up again. I just took the compass from my rucksack to check the azimuth of a dish for the OSCAR100 satellite, and found that the compass had reversed. Probably caused by earbuds (headphones) in the same storage pocket.
I should probably take Andy’s advice from higher up the thread:
Perhaps by now someone is making a compass with a permanently magnetised needle? A quick google didn’t find anything, but is there any reason why not…?