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New tool - toroidal ferrite core inductor calculator

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by SP3L, Jun 14, 2021.

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  1. AC6LA

    AC6LA Ham Member QRZ Page

    Jacek is probably in bed now so I'll take a shot at this.

    Here's a comparison for 10 turns on a single core for Fair-Rite #31, Fair-Rite #43, and Amidon #43.


    At 7 MHz the Fair-Rite #31 and #43 results are very similar. The Amidon #43 is noticeably different. Amidon has changed suppliers and their #43 material is now not the same as Fair-Rite #43.

    Here's a comparison sweep from 1 to 50 MHz.


    Of course ferrite cores are not precision parts. Results ±20% are to be expected. And the method of winding the turns along with any influence of nearby metallic objects also is not taken into account by the TFCI Calculator.

    Dan, AC6LA
  2. SP3L

    SP3L Ham Member QRZ Page


    I checked those two cores with 12 turns. And the results are identical.


    We have something wrong.
  3. SP3L

    SP3L Ham Member QRZ Page

    I can not recreate it now any more.
    It seems to me that in order to recreate the problem, you need to start changing the setting in the calculate sheet before agreeing to enable macros.
    Once the macros are enabled everything works correctly.
  4. AC6LA

    AC6LA Ham Member QRZ Page

    I must admit that it never occurred to me that anyone would attempt to use the calculator without enabling macros. Every drop-down, every button, every checkbox invokes a macro. And when any of the Option A/B/C drop-downs are changed there is usually a cascade of macros that must be run in the proper sequence.

    Not enabling macros is similar to removing all the cell formulas from a standard workbook, such as "=B1+B2" in the A1 cell, and then wondering why the workbook seems to be broken.

    With newer versions of Excel (2010 and newer) once the "Enable Content" or "Enable Macros" button is clicked that setting should be remembered for that workbook name in that folder. The exception would be if "Disable all macros without notification" was chosen after clicking File > Options > Trust Center > Trust Center Settings > Macro Settings.


    But even with that choice I believe a warning will still be shown. I just now created a copy of the TFCI Calculator with a different name, opened that new workbook, ignored the "Enable Content" button, then clicked one of the drop-downs. That resulted in this warning:


    Dan, AC6LA
  5. SP3L

    SP3L Ham Member QRZ Page

    The error occurs when you:
    1) open the workbook for the first time ever and ignore the warning about edition enabling displayed at the top of the workspace
    2) switch to the Calculate sheet
    3) enable the editing in response to the warning message displayed at the top of the workspace
    4) ignore the second warning displayed at the top of the workspace about enabling macros
    5) change the material in the option A
    6) click OK on the error message window that pops up
    7) enable the macros in response to the warning displayed at the top of the window

    If you do everything in this order, the calculator seems to work, but the option A shows 31 material but use the 43 material data (default setting right after opening the file). If you close the workbook and reopen it, Excel remembers that macros are enabled for this file and everything works OK.

    So, this is not the error in the calculator itself but the unexpected reaction of the user for the Excel warnings.
  6. VK2TIL

    VK2TIL Ham Member QRZ Page

    Dan; you said ... At 7 MHz the Fair-Rite #31 and #43 results are very similar. The Amidon #43 is noticeably different. Amidon has changed suppliers and their #43 material is now not the same as Fair-Rite #43. ... .

    Fair-Rite has tinkered with the #43 mix over the years; they have published four different sets of u'/u" data to my knowledge, the fourth appearing as recently as Nov 2020.

    Perhaps Amidon have not changed suppliers; perhaps they have just not changed the data on their website which shows the older #43 with ui of 850 (the later mixes have ui of 800).

    My guess is that Amidon are selling the later (ui = 800) #43 material but providing data for the earlier (ui = 850) #43 material on their website.

    Confused? I certainly am!

  7. SP3L

    SP3L Ham Member QRZ Page

    Indeed, we are all confused.
    It seems that Amidon have change supplier from Fair-Rite to National Magnetics Group, Inc. but they kept the old material designators from Fair-Rite.
    NMG uses quite different material designators but if you compare the datasheets on the Amidon website and NMG website, they are identical.
  8. AC6LA

    AC6LA Ham Member QRZ Page

    Here's a comparison of "old/original" (pre February 2020) Fair-Rite #43 vs the latest (Feb 2020) $43.


    Owen Duffy did a nice blog post on the subject. Apparently the change in the u'/u'' curves was partly due to a change in the material composition and partly due to more precise measurements.

    Here is an extract from the Amidon datasheet for their #43 ferrite.


    And here is an extract from the National Magnetics Group datasheet for their type "H" ferrite.


    And finally, a comparison of the NMG "H" u'/u'' curves and similar curves from the Fair-Rite datasheet for their #43 (Feb 2020) ferrite.


    Edit to add: I see Jacek already answered the question while I was busy creating all sorts of fancy illustrations. :confused:

    Dan, AC6LA
  9. AC6LA

    AC6LA Ham Member QRZ Page

    Yes, "Enable Editing" is not the same as "Enable Content". The "Enable Editing" prompt can be avoided by right-clicking on the downloaded zip file, selecting "Properties", then clicking the "Unblock" button.


    In addition to avoiding the confusion about "Didn't I click that already?", doing the Unblock will also preserve the original date of the workbook (and the Help file) rather than assigning the date of the download.

    Dan, AC6LA
    SM0GLD likes this.
  10. SM0GLD

    SM0GLD Ham Member QRZ Page

    I get an Excel warning saying:
    "It is not possible to draw negative values or zero values in logarithmic diagrams. Only positive values can be interpreted on a logarithmic scale"
    Shall I ignore this, will displayed values still be correct?

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