ad: dxeng

Identifying Toroidal Cores

Discussion in 'Homebrew and Kit Projects' started by KE7AQL, Jul 15, 2008.

Thread Status:
Not open for further replies.
ad: L-HROutlet
ad: l-assoc
ad: l-innov
ad: l-Waters
ad: Subscribe
ad: L-rfparts
ad: l-rl
ad: l-gcopper
  1. KE7AQL

    KE7AQL Ham Member QRZ Page

    I need to wind some toroids for a project that I'm working on and have a few cores laying around.
    Is there any way to identify what the ferrite mix is (ie. 43, 63, etc)?
  2. KB2YYR

    KB2YYR Ham Member QRZ Page

    Not easily, no. About the best you can do is wind a known number of turns on it and accurately measure the inductance. That will get you in the ballpark. If you can measure the inductance across a range of excitation frequencies, so much the better.
  3. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    ::Cores are often color coded to help you identify the mix; unfortunately, many aren't and even with those that are, you'd have to know the manufacturer of the core to trace back exactly what the color means.

    When I "buy" cores (thankfully, they're pretty cheap!) I buy them according to the mix, diameter and thickness and once I get them I always "color code" them myself to remind me later what the heck I have. I use small dots of colored paint. Mix 43 would be yellow-orange, two dots side by side. Mix 75 would be violet-green, two dots side by side, etc. That way, even many years later, I know what I have.

  4. KR2D

    KR2D Ham Member QRZ Page

    A few years ago, I read a web page that explained how to the identify ferrite mix with a MFJ antenna analyzer. Of course I didn't bookmark it. When I bought an analyzer, I wanted to ID the ferrites in my junk box, and now I can't find the web site.

    Not helpful, I know. But maybe someone out there knows of that web page and can provide a link.
  5. AB8RO

    AB8RO Ham Member QRZ Page

    Here ya go, from my old stomping grounds.
  6. M0DSZ

    M0DSZ Ham Member QRZ Page

    Have a look at this site. It is important to distinguish between iron-dust and ferrite cores, if you're using any kind of power the ferrite will probably saturate easily, produce non-linearity and harmonics, become hot and even disintegrate.

    Typical manufacturers are Amidon, Ferroxcube, Fair Rite and Micrometals. Amidon use colour codes for their dust toroids and the same code is emulated by some lesser manufacturers. In the case of unmarked, colourless toroids, as contributors have already said, try a few turns at various frequencies and see what happens. Bear in mind that some materials are deliberately lossy and designed for EMC reduction, still quite useful though on power leads for that purpose.
  7. WB2UAQ

    WB2UAQ Ham Member QRZ Page

    Once you get a core of known mix, use the MFJ unit, measure it and record what found for future reference. The color coding is good too.

    I have had good results ID'ng cores by measuring their physical dimensions with a caliper and then using a low freq LC bridge (the common 1 kHz types, not sure if the cheap multimeter types would be of any use) with some turns applied to the core, measure the inductance and calculate the AsubL (inductance factor) (from the number of turns and inductance measured). Then go to the catalogs and match the AsubL you calculated against the core size you measured. The initial perms are determined at low freqs so using 1 KHz works very well.

  8. KE5FRY

    KE5FRY Ham Member QRZ Page

    Am I correct in assuming that the ones i have that are magnetic are powdered iron and the non-magnetic ones ferrite?
  9. ZL3GSL

    ZL3GSL Ham Member QRZ Page

    non magnetic toroids

    No. ;)

    Ferrites, and iron powder are both ferromagnetic.

    Non-magnetic toroids might be "grade 0", made of phenolic, to be used as a former when you need a toroidal coil with a core mu of 0. :cool:
  10. KB1KIX

    KB1KIX Ham Member QRZ Page

    I've been looking through things before I throw them away and taking the cores and a few other odd parts here and there and storing them.

    I have a whole bin full of 'em that I really want to identify.

    Of course, purchasing them from Diz (The Toroid King) also works.....

    I also picked up the little kit from "QRPMe". Rex sells a plastic handle that is wicked nice for when you have to wind them small suckers. If I ever lose or break this thing.... it will be a sad day. Makes winding them a whole lot easier.

  11. PD7MAA

    PD7MAA Ham Member QRZ Page

    any toroid..

    From my club president PA0EJH:
    If you need to find out if a toroid is ok for your project:
    put 3 turns of wire on the unknown ring and attach them to a signal generator .Then wind 3 turns on the other side and attach these to your scope. The sinus of the signal schould be the same on each side .If not the toroid is not designed for your frequency.
    This is the best way to identify rings of unknown origine.
    73s John
    Last edited: Sep 14, 2008
  12. PD7MAA

    PD7MAA Ham Member QRZ Page

    How to calculate the AL of a onknown toroid

    1 Wind 3 turns of wire on the unknown toroid
    2 measure the induction in uH
    3 Multiply the outcome by 1000
    4 devide the outcome by the square of the windings ( 9 )

    73s John
  13. K9FV

    K9FV Ham Member QRZ Page

    John, I really hate to show my lack of knowledge here, but what does the answer give you? the mix - i.e. 43, 61, etc? Or a number to allow you to look up the mix?

    on edit: Should this be at a special freq? 2 mhz? 1 khz? My inductance meter is at 1 khz (I think), but the MFJ259B can be at much higher freqs.

    73 de Ken H.
  14. PD7MAA

    PD7MAA Ham Member QRZ Page

    Hello Ken
    Amidon mix numbers explaine the AL
    My intention is to help OM's with unknown toroids. By knowing the AL the OM can choose the perfect match for a certain frequency or , as you mentioned , find out the mix. Products of Amidon can normaly easy be recognized by size and coulor...
    To check the inductance i use a AADE inductance meter.
    73s John
  15. K9FV

    K9FV Ham Member QRZ Page

    Awww, dummy me - now I see what you are doing John. take the reading in microhenry, multiply 1000 to get the reading in henrys, then devide by the turns squared to get the value in henrys for a single turn of wire.

    Shucks, sometimes I can't see the forest for the trees.

    That AADE sure is nice. I just build my meter last week. Sure does give a LOT better readings for capacitance and inductance than the MFJ-259B. Just too hard to cancel out the lead inductance/capacitance in the MFJ.

    edit: BTW John, using the AADE meter, why put 3 turns of wire thru, then calculate? Why not just pass a single turn of wire thru and measure that - would that be less accurate?

    73 de Ken H.
    Last edited: Sep 22, 2008
  16. KL7AJ

    KL7AJ Ham Member QRZ Page

    Actually, this method will get you not only in the ballpark, but to first base. The variation in permeability between cores of the same material is often greater than the error in this calculation. :)

  17. PD7MAA

    PD7MAA Ham Member QRZ Page

  18. K9FV

    K9FV Ham Member QRZ Page

    That is perhaps the best program I've seen for torids John, that's a good one. has some pretty good info also.

    I also downloaded the beacon program - simple and neat!

    Ken H>
  19. W8JI

    W8JI Ham Member QRZ Page

    Measuring the slope of reactance or impedance doesn't work to sort most ferrite cores.

    What you have to do is wind a few turns on the core, enough to get a releiable reading for the measurement device you are using, and then sweep frequency until X=R. Reactance equals resistance.

    What you will find is various cores have X=R at certain frequencies, this is where the loss tangent and reactance cross, or the Q=1 frequency.

    For example 73 Material X and R cross at around 2 MHz. 43 materials cross up in VHF.

    If you are using an MFJ-259 try to do this with enough turns so that the R is 50-100 ohms at the crossing frequency. Keep the core RIGHT AT the connector!!!!

    If you are looking at low mu powdered iron cores, then you can just measure inductance. Using just a few turns, maybe a half-dozen, look at the value of inductance and the slope of inductance with frequency. The Q will probably be too high to use reliably unless you have a professional instrument. You can calculate AL and try to match it to a core, but this is not very reliable because several different types have similar AL's.

    Actually a very low ui core is difficult to sort out. High ui mixes are pretty easy.

    73 Tom

    (Only LIDS mix politics, religion, and radio.)
    Last edited: Sep 27, 2008
  20. K9FV

    K9FV Ham Member QRZ Page

    Thank you for the info Tom - I will be playing with your suggestions over the next few days and see if I can make it work.

    This is just one of the areas where I'm always interested in learning something new.

    73 de Ken H>
Thread Status:
Not open for further replies.

Share This Page

ad: M2Ant-1