PULSERs ONLY

[nong]

Thank you for video file.   

[hartiberlin]

Hi EMdevices,
surely this is strange !
Normally a ferrite core of a coil should be saturated in both
directions, so itshould not matter, if you put the south or
noth pole onto the ferrite core...

Hmm, the only thing this could
probably be like it was shown, if you have  a DC current flow already superimposed inside the coil
at the working point ,
so the ferrite is itsself already a magnet and you just change only its BH curve
magnetisation level by aproaching the magnet.

What happens, if you use a very strong neodym magnet ?
Still the same or does the sticking of either pole onto the ferrite core
give then always a higher frequency ?

[EMdevices]

Hi Stefan,

The earth magnetic field already saturates the ferites somewhat, when no magnet is present.Ã,  Much like a DC current will.Ã,  But there is no DC current in the coil.Ã,  It's only the earth's magnetic field that biases the ferite.

So the small magnet when it opposes the earth magnetic field, it cancels the flux around the ferite and "simulates" a condition free from magnetic fields.Ã,  Ã, 

In this ideal situation,Ã,  the ferrite is close to zero on the B-H curve and we get the most out of it in terms of magnetic domain flipping and the largest inductance.Ã,  Neodymium magnets have the same effect albeit more pronounced.Ã, Ã, 

Basically this is a qualitative experiment to realize the earth's magnetic field does affect circuits, it sets the bias point, but we don't always worry about it, or realy need to worry, I suppose. 

It is quite interesting though.  It took me by surprise as well.  The ferrite has AC in it only (from the coils), but also seems to have static fields from the magnet/earth's magnetic field, which sets the bias point.

EM

[EMdevices]

Ok, here's a video you will love.

NMR in action I suppose !!

EM

[hartiberlin]

Hi EMdevices,
hard to say what is going on, if we don?t know the circuit diagramm you are using...

Maybe you just hit with the ferrite stack better the resonance frequency
of the LC tank excitation and then shift the inductance to be rightregime, so
it gets in better resonance ?

2. In your first video, how was the ferrite core coil on breadboard being used ?
Was there no DC bias current through it ?