Ferrite for baluns

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KC0LWN, Feb 8, 2015.

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  1. KC0LWN

    KC0LWN Ham Member QRZ Page

    Hello I am planning on winding my own baluns but not sure what material to use.

    I already own some ferrites in mix 31 mix J Mix K
    Which should i use for a 4:1 balun for 80-10 meters?

    Thank you.
  2. W5DXP

    W5DXP Ham Member QRZ Page

  3. WA7DU

    WA7DU Ham Member QRZ Page

    Just when I was getting comfortable thinking and talking about ferrite mixes designated with a two character numeric (mix 31, mix 43, mix 61, and so forth), up pops Cecil talking about "type K." What does "type K" mean?

    A quick perusal of the G3TXQ link didn't reveal any reference to "type K."

    Cecil, the ball is in your court, but I'll welcome anyone who can answer the question.
  4. G3TXQ

    G3TXQ Ham Member QRZ Page

    Type K is an older mix that is no longer manufactured - I think Cecil had a number in his "parts box"! The newer #52 mix is very similar in its characteristics, and can be very effective in the mid-to-upper HF region. The 11th line on my chart shows an example.

    Steve G3TXQ
  5. KU3X

    KU3X Ham Member QRZ Page

    You can fine tune a balun with a lot of different mixes, but you'll find that #31 is one of your best choices. You can also use 43 since you are not going to use 160 meters.

    Reference: http://audiosystemsgroup.com/RFI-Ham.pdf

    This is the best information I ever found on the internet, "BAR NONE !"

    W2FMI set the ground work for baluns and Jim Brown took it from there.

    I made a 4 to 1 Guanella Current balun using #43 cores and was able to keep the return loss better than 20 DB. This equates to a balun that is 99 % efficient from 10 to 160
    meters. Refering to K9YC's information, the choking reactance is over 1000 ohms on the HF bands.

    You can use your K material if you like, it will do a great job, but #31 is a better choice.

    Last edited: Feb 8, 2015
  6. KM1H

    KM1H Ham Member QRZ Page

    While the 52 mix shows some benefits it is not available in the 2.4" toroid such as the very common 31 and 43 mixes. For your needs the 43 mix from Mouser is the best bang for the buck.
    Part 2643803802 at $4 with low shipping cost if you specify USPS First Class for up to 13 Oz. Arrow has them at $3.43 but last I looked they had minimums and higher shipping.

    I completely agree and always recommend it be read.

    While his basics were sound, unfortunately Sevick never got it right as all his book Revisions had errors especially where it got away from small signal lab testing to assumptions made for power handling.

    Last edited: Feb 8, 2015
  7. G3TXQ

    G3TXQ Ham Member QRZ Page

    The 52 mix is readily available as a 2.4" toroid: Fair-Rite part 5952003801; Mouser stock 623-5952003801. But it's immaterial because the OP says he already has Type 31 and Type K ferrites available.

    In addition to thinking about the ferrite mix, he might want to consider the design of balun. If it's a 4:1 current balun he needs there are better options than a 4:1 Guanella.

    Steve G3TXQ
  8. KM1H

    KM1H Ham Member QRZ Page

    Thanks for that info, I was mistakenly searching the wrong category but with a permeability of 250 it offers little over a 43 mix at more cost.
    I'll get a few with my next order and see how they perform.

  9. G3TXQ

    G3TXQ Ham Member QRZ Page


    The lower permeability enables you to increase the number of turns without getting the low SRF that the extra inter-winding capacitance gives you with a higher permeability core. It's not as widely useful as #31 or #43 but it does make a particularly effective choke in the range 10MHz - 30MHz:


    That's 9 turns on three stacked FT240-52 cores. And this is 11 turns on two stacked FT240-52 cores:


    I've never achieved anything quite that good in the mid-upper HF range with #31 or #43.

    Yes - the cores are a little more expensive, but seeing what folk pay for radios and antennas these days it's down "in the noise". I was surprised to find them readily available through Mouser UK.

    Steve G3TXQ
  10. KM1H

    KM1H Ham Member QRZ Page

    And this is the Fair-Rite results using less turns on a single core.


    For ham use there is minimal difference when feeding a 50-75 Ohm antenna at legal power.

    How do the two compare when there is considerable +/- reactance such as trying to cover all of 10M with a trap yagi?

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