Compass effect

[Mike(Mont)]

I don't know much about this and was hoping someone could enlighten me.

I was working with a coil and noticed when i moved to a north/south direction the coil produced a strong signal. No amplifier just connected to a multimeter. I assume this is what some call the compass effect. the coil needs to be moving through the flux lines for this to occur. The same principle how a generator works--move a conductor through a magnetic field to produce electricity.

[WM6]

If coil is part of working oscillator, oscillation act as movement substitute in Earth magnetic field.

In case of bare coil in Earth magnetic field, it is important, if coil is placed along or transversely to Earth magnetic field lines. If placed along even small movements are enough to sense some inductive response at coil ends (if coil is proper wound: enough L and high Q).

[Mike(Mont)]

So you need to overpower this effect? Or how do you eliminate this?

[Geo]

If the coil is at input of receiver then the low gain is a solution. If it is part of oscillator then it is big story!!!.
If the coil is on a ferrite then the material of ferrite has the first place.....

[Mike(Mont)]

Okay, thank you. Big coil seems to be the problem. 55 cm square loop 140 turns 26 AWG magnet wire tuned to about 36.75kHz. No amplifier. Huge compass effect. I was reading AC amps. Maybe I am picking up a VLF station in Iceland NRK. (My tuning might be off a bit.)

[Mike(Mont)]

Think I need to do a little work on this. Something is happening but it is not very consistent. My observations are not set in stone. Not even sure about the compass effect or not. Pretty much total confusion at this point.

I recall airplane compass have some sort of variations when turning. Can't recall but when you turn towards north, the compass needle speeds up or slows down depending on which direction you are coming from. I suspect the same thing happening here.