Why is the subject of choke baluns such a complex and involved one?

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by VK4FUQ, May 4, 2021 at 9:32 AM.

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  1. VK4FUQ

    VK4FUQ Ham Member QRZ Page

    G'day all, yes I know that this subject has been 'done to death', as it were yet the more that I read (on the internet mainly), the more confused that I sometimes get! Yes I know that the subject is constantly evolving, however quite a bit that I read (on the 'net), is essentially wrong in the technical sense.

    For example I still see powdered iron core material recommended for simple 1:1 choke baluns when it is inherently very low permeability severely limits its low frequency performance. Ferrites are 'always' better!

    Speaking of 'ferrites', I am endlessly baffled by the many different 'mixes' that seem to be the 'flavours' of the month! My favourite 'balun' book is Sevick's 'Transmission Line Transformers' 3rd edition, and although somewhat dated now, has all the required reference material that I need, and regarding ferrites per se, the 61 material (ui 125) is recommended for many of his designs (including the lowest loss) and many of my own DIY designs are modelled on Sevick's designs, and in many cases, and are wound on 125 ui ferrite rods and work perfectly.

    So why is the present balun state of the art so seemingly complex and involved when it doesn't apparently need to be? Regards, Felix vk4fuq.
    Last edited: May 4, 2021 at 9:44 AM
  2. WA4SIX

    WA4SIX Ham Member QRZ Page

  3. KD9VV

    KD9VV Ham Member QRZ Page

    "So why is the present balun state of the art so seemingly complex and involved when it doesn't apparently need to be?"

    Your question begs the question. "Why sweat it?"

    There are many hams; some are ok with a wet noodle to tx and rx.
    Then there are those who rival professional physicists. LOL

    The Balun question can and does get very complex when one considers the variables of so many different antennas, radiation patterns, coax type, coax length.

    Personally; I am one who refuses to be pulled in with analysis paralysis.

    Currently I am replacing my coax to a 5ele 6M LFA antenna.

    I've been actively involved in multiple discussions..choke or balun...air wound or ferrite?

    It is amazing the number of opinions out there based largely on voodoo; and this is a problem.

    So; I will be using ferrite, (Mix 31) at my feed point. Will it work to mitigate CM noise? Who knows?
    Technically it should.
    W/o test equip I won't know how effective it is.

    How will I know if it works?..HELLO CQ?
    VK4FUQ, PU2OZT and K0UO like this.
  4. KK4NSF

    KK4NSF Ham Member QRZ Page

    not being a choke balun guru, or even a casual user.... I don't get it either. what i do know is that there are a few folks who think they are a must-have item, while others disagree completely. The two groups look to be totally polarized....with one side tossing out all sorts of data, papers, and complexities, and the other side always saying "oh bullshit". Personally, I think both sides are muddying up the waters on this topic.

    So...what's the deal with 'em? I don't know, but my antennas seem to work without them. Would they work better with them? Maybe.
    KD9VV likes this.
  5. WA7ARK

    WA7ARK Ham Member QRZ Page

    Yep, especially while receiving.

    ...and don't screw with ugly coax chokes.
  6. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    It's unlawful to own ferrets here in California.

    And that's no choke.
    SM0GLD, KN6KDT, K1LKP and 5 others like this.
  7. KK4NSF

    KK4NSF Ham Member QRZ Page

    well there we have it: a straightforward answer. thanks.

    that does however bring up a new question: my receive antennas all use small impedance matching transformers. in that case, would a choke balun do aything that is not already being done by the transformer?
  8. KK4NSF

    KK4NSF Ham Member QRZ Page

    I heard they taste just like chicken.
  9. WA7ARK

    WA7ARK Ham Member QRZ Page

    A proper isolated-winding RF transformer also has very high Common Mode Impedance, usually better than a choke. Unfortunately, they have an insertion loss that is too high to be placed in the transmit path...
    Last edited: May 4, 2021 at 2:46 PM
    KK4NSF likes this.
  10. G3YRO

    G3YRO Ham Member QRZ Page

    The bottom line is to try it yourself . . .

    Put up a Dipole with the wires soldered direct to the coax . . .

    Then put a choke balun (coax wound through a Ferrite Ring) at the feedpoint, and see if it makes ANY difference to the Resonant Frequency or the received noise level.

    If it DOESN'T (or makes very little difference), then you know you had no Common Mode Current worth worrying about.

    Whether Common Mode is a problem depends on lots of things, mainly the length of the coax feeder on the band you're working on. In my 50 years of HF experience, it's rarely a problem !

    Roger G3YRO

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