How to identify Ferrite Mix

[OA4AJP]

Dear All:

I have bought 8 ferrites toroids 4x FT240-43 and 4x FT240-31.

Is there a way to identify from which mix is each one?

Can I use an Inductance meter to identify the Ferrite Mix (31 or 43)?

Regards.
Alfredo Mendiola Loyola
Lima, Peru
OA4AJP

[NW2K]

You might consider weighing them. #31, in that size, weighs approximately 112g-116g.

[KD8DEY]

Are the ends color coded?
http://sharon.esrac.ele.tue.nl/~on9c...#kleurcodering

[G3TXQ]

I just weighed three FT240-31 toroids and three FT240-43 toroids: each of the FT240-31s weighed 114gms and each of the FT240-43s weighed 122gms.

If you have an analyser, checking the "crossover frequency" (where R=X) can also be a useful indicator.

The first thing I do now when I buy them is mark them with the mix type - I learned the hard way! Mind you I have had situations where the supplier got them wrong

73,
Steve G3TXQ

[KU3X]

Yes, you can check them with an inductance meter. Put about 5 or 6 turns of wire through the
core to be tested. Take the same reading on both cores. The 31 mix will have more inductance.

Barry, KU3X

[OA4AJP]

Dear All:

My toroids have no colors, they are gray.

I will test them with an inductance meter.

Thank you for your help

Regards.
Alfredo Mendiola Loyola
Lima, Peru
OA4AJP

[G3TXQ]

I will test them with an inductance meter.

Make sure you do it at a low frequency - well below the SRF of the winding; otherwise you can get misleading results.

Steve G3TXQ

[OA4AJP]

Results:

Ferrite 43:
5 turns
0.022 mH
22uH

Ferrite 31:
5 turns
0.052 mH
52 uH

Frequency 100Khz

Regards.
Alfredo Mendiola Loyola
Lima Peru
OA4AJP

[OA4AJP]

I have tested my balun using a FT240-43 with 17 turns of RG-58, the RFI in my shack has gone and the SWR has not changed.

Regard.
Alfredo Mendiola Loyola
OA4AJP

[KM1H]

Thats the good news.

Now see what the minimum turns are required for both mixes; spread the turns to cover most of the core. Excessive turns could cause other problems that would require a VNA to see.

Carl