To Balun or not to Balun?

that is the question, for many ham radio operators. A simple, resonant, single band, plain-vanilla horizontal dipole, does really need a 1:1 balun… or not?

To investigate the differences between a dipole having a 1:1 balun and another one directly connected to the coaxial cable, I build a 40m band dipole with a remotely controlled switch that could bypass the balun on demand:

switched_balun

Then I conducted a few experiments that I have documented in a video.
I hope you’ll enjoy it!

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5 Comments

  1. Bonjour,un balun 1/1 ne peut étre en totalité imperméable de 3,5 à 30 mhz quelques soit ça conception (tore ou baton de férrite) à mon avis pour assurer un minimun de distorsion il est préférable d’utiliser un balun 1/1 pour seulement les dipoles et si possible en conception coaxiale.Pour une antenne multibande alimenté avec du cable coaxial il est conseillé de ne pas en utiliser car il peut compliquer le fonctionnement sur certaines fréquence.Pour une antenne multibande,utilisé plutôt une alimentation à ligne bifilaire (300-450-600).
    Un balun 1/1 de bonne conception en cable coaxial ne provoque aucun ros supplémentaire.

    • Hello Tom.

      Of course you can use this video on your live show!
      Let me know when you schedule it, so I can watch it. Are your live shows recorded and made available for offline viewing? 0100UTC is 03:00 AM here.

      Vy73 de Davide IZ2UUF

  2. I have watched your video and looked at the picture above and it seems that your switching changes the lengths of the dipole elements and therefore the balance of the dipole.

    It appears that the right hand side of the dipole is always connected to the inner of the coax and the left hand side of the dipole is switched to be connected directly to the outer of the coax or connected to both ends of the outer of the coax.

    I would suggest that this method of switching changes the antenna circuit as one leg of the dipole is always passing through the coaxial cable where as the other leg is switched in and out.

    While this may switch in and out the effect of the balun I think it also changes the antenna characteristics of the antenna which may also give the results you have observed.

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