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Discussion Forum - The Bothy - Compass mystery-reverse polarity


Posted: Thu 7th Oct 2010, 22:40
Joined: 1972
I had a problem with a new Silva compass that had become de-magnetised. Of course Sod's Law kicked in when I first took it out to follow a bearing on the Continental Divide Trail in Wyoming. So a useless device and miles from anywhere but at least the sun was shining sufficiently to give me an approximate direction.

I pondered the problem and concluded that, as I had the compass in my jacket pocket when I passed through airport security, the metal detector arch must have de-guasseed the needle.

Back in the UK I returned the dam thing to the Black's branch where I bought it and I congratulate them on customer service. They directed me to select another of the same model. Returning it to the cash desk they swiped it over the counter to de-activate the security tag on the packet.

Aha! Could the security system use an A/C electomagnetic field to de--activate the tag? If so needle would be de-magnetised. The cashier thought just so and sent me off to get another compass. This time he cut off the packaging, swiped it over the security system and handed me the now unpacked compass. I wondered if the security arches on the store exit would do the foul deed again but outside the compass needle pointed as it should. So next time you buy a compass be advised to check that it is still functioning after you leave the shop'spremises.
Posted: Mon 29th Mar 2010, 11:50
Joined: 2010
Your compass will also be attracted by iron. In my old days in the Army we were told to move away from vehicles and keep it away from the rifle, binoculars, radio etc. Even a chunky iron fence will deflect the compass by a ew degrees if you stand close enough, so don't lean on a wire fence while setting a bearing.
Author: W. Paul Tremere
Posted: Sat 25th Jul 2009, 21:50
Joined: 1989
Local Group: East Yorkshire
In the olden days before digital technology and satellite navigation I had the bright idea of recording night-time route descriptions on a hand-held tape recorder. This avoided scrabbling around in the dark attempting to read the route description with a head torch. Although the machine was surprisingly heavy and I often had to rewind bits, the system worked quite well, enabling me to plod allong through the night listening to my own directions. Until ......... I had to walk on a compass bearing. With compass in my right hand and tape recorder in my left, strange things began to happen. It took me some time to realise that the tape recorder relied on magnetic tape and contained a magnet. From then on the recorder and compass were kept well apart.
I guess that this will not happen with today's technology, but the moral is clearly, that compasses and magnets don't mix!
Author: Eileen Greenwood
Posted: Mon 13th Jul 2009, 17:11
Joined: 2002
Local Group: Yorkshire Coast
Oh just what i like- a couple of totally useless suggestions! (just joking).

Actually I have solved the problem with my compasses. The answer is my Nalgene hydration system.

The head of the tube has a magnet on it( I discovered this by accident when it stuck to the fridge door!). The magnet is supposed to be a useful device for attaching the mouthpiece to the the clip of the rucsac. However most clips on rucsacs are made of plastic anyway so it isn't of any use and reverses the polarity of compasses as they hang from your neck!!

I have reversed both back to the correct polarity now using the same magnet! And yes Alan- you don't get these problems with GPS! I have 1 but don't know how to use the way marking bit!
Author: Alan Greenwood
Posted: Sun 12th Jul 2009, 21:22
Joined: 1998
Local Group: Calderdale
Buy a GPS and then you will never be lost unless the batteries go flat.
Author: Tony Deall
Posted: Sun 12th Jul 2009, 20:32
Joined: 1985
Local Group: Cumbria
Or you could try walking backwards, Eileen
Author: Eileen Greenwood
Posted: Sun 12th Jul 2009, 19:48
Joined: 2002
Local Group: Yorkshire Coast
I have had 2 compasses reverse polarity on me in 2 successive years! I had a Silva compass for years then used it on a reccy of a route on the North Yorks Moors a few times last year. It reversed polarity. I got another one and again used it on the same route reccy (those heather footpaths are a nightmare!) and lo and behold it reversed polarity again damn it!!

Now I ask- what would make 2 compasses reverse polarity when it is supposed to be a rare event I think? Has anyone else had this problem? It is not my house as I had the old one years until the reccy of the moors. And the new one was OK until I used it again on this section. Could it be electric pylons that I have to go under a few times? Or the rocks on the moors? My gut feelings are the pylons.

Any ideas!! In any event I am not going to buy another one! I shall just use it (or the old one) and remember it has reveresed its polarity! Maybe if I go over the route again it/they may reverse back again!

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