testing ferrite cores

[p.larner]

i have about a dozen cores from a collins radio amplifier pcb,is there a way to check there suitability for hf baluns/chokes etc,i have a 50mhz scope a 0-450 mhz sig gen and a nanovna.

[Slh]

Measure the dimensions. Stick 10 turns on it and measure the impedance and inductance 50kHz to 1Mhz and 1Mhz to 100Mhz. Divide inductance at around 50kHz by 100 to get Al

Take all that info and have a rummage through the micrometals and fairite websites to find something similar.

[p.larner]

what am i best using to do those tests?.

[Roehrenonkel]

what am i best using to do those tests?.

...get a scope and generator that can do MHz. ;->

[Andy Chee]

Characterising an unknown ferrite toroid

https://owenduffy.net/blog/?p=5198

The ‘unknown' toroid is wound with a single turn and measured with a VNA.

The frequency where R=X or µ'=µ” is an interesting one, combined with µi it is a useful short signature that can be used to identify / classify common materials.

[coppercone2]

you have entered the ferrite sorting epoch

pretty soon filters and power supplies will begin to condense

[p.larner]

well i am homebrewing another atu,i have a homebrew t match that works fine,my latest project is an L match,i wanted to use the torroids for the directional coupler to feed the twin needle meter,was concerned over the linearatiy over freq,waiting on parts at the moment,on a slowboat from china,the twin needle meters run at about 30 pounds on ebay uk on aliexpress they are 11 so i can wait.,i could buy one( coupler) already made but want to build one from my junkbox bits! 73.

[A.Z.]

toRoids not toRRoids, those are mostly like hemoRRoids but not as efficient

[Smokey]

[Randy222]

The vid posted by Smokey is ok method, but I just make the dut an inline item between S11 & S21, sweep it, and find the dip.

I got a pack of unknown beads on wire from amzon, no real data, just "ferrite bead inductor".
I solder a bead between two sma connectors, and grounds connected, connect between S11 & S21, sweep it, and I find I have 100kHz ferrite beads, -40db @ 100kHz. I use LiteVNA64.
The vid makes point to 1st calibrate at the ends of the cables, which is good for more accuracy, but not really needed to find the dip where the ferrite is providing some attenuation.

I actually needed to test the beads I bought, I find they will not be correct for my PSU filtering project, I need an FR31 ferrite.

As for OP ferrite unknowns, wrap a few turns of magnet wire around your ferrite, sweep it with the VNA, S21 log graph should indicate where the impeadance peak notch it.