A question of coil coupling

[pebe]

I have an omega coil that has not been nulled properly.

Assuming an undercoupled coil gives an Rx output with a certain polarity, does an overcoupled coil give the opposite polarity?

[simonbaker]

I have an omega coil that has not been nulled properly.

Assuming an undercoupled coil gives an Rx output with a certain polarity, does an overcoupled coil give the opposite polarity?

Depends on what you mean by "output" and "opposite". The null signal will be shifted to sort of opposite, not necessarily 180 deg, could be in between.

I think a target signal may not shift much at all, but that is a question I need to test myself.

-SB

[Carl-NC]

I have an omega coil that has not been nulled properly.

Assuming an undercoupled coil gives an Rx output with a certain polarity, does an overcoupled coil give the opposite polarity?

Generally, yes.

[pebe]

Thanks to you both. I thought that would be so. I cannot get at the coils without sawing open the case, and I dont want to do that. So I intend to null them electrically by means of a delayed sine-wave from the Tx coil injected into the preamp. I have done a circuit for my own Micronta but if the circuit was to be of any use to others, I thought I would need to allow for the non-nulled signal of either polarity.

[Altra]

The "Old Timers" use to renull the coils by glueing a coin to the top of
the coil. You move it around until you get the best null and tack it down on that spot. Try different sizes and metals.