VHF-UHF Baluns

This is the talk that I presented at the RSGB Convention in October 2018.

RSGB will eventually release a video of the talk, but in the interest of publishing the technical content as soon as possible, you’re very welcome to download and click through the slideshow.

Even without the voiceover, the important points are clear:

  • Today, “baluns” are about controlling interference, reducing noise
  • Choke baluns are best for doing this.

So we should aim to:

  • Minimize common-mode RF currents on the outside of the coax
    and along the boom.
  • Don’t upset the good feedpoint balance that VHF-UHF Yagis already have.

Comments and discussion, please!  This is new information for VHF-UHF, and certainly not the last words to be said about it. It’s still very much ‘work in progress’.
Leave a reply

 

Technical slide content © 2018 Ian White, GM3SEK
Slide template © 2018 RSGB
Images as attributed (except where that would be embarrassing).

2 thoughts on “VHF-UHF Baluns

  1. Conrad Farlow

    Hello Ian, this is very interesting indeed and very timely. I am building quite a few systems at the moment and I was going to just put a string of ferrite cylinders on the coax. On my dual band 4m and 6m antenna I used ferrite without shorting to the boom. However on my new 2m and 70cms antennas I will do exactly what you have described.

    It is a minefield of misinformation! Thanks very much for taking this to on.

    Regards

    Conrad PA5Y

    Liked by 1 person

    Reply
  2. Jim Brown

    Kudos on your excellent piece on VHF chokes. Another good solution for 2M is a string of #31 solid or 0.5-in i.d. clamp-ons. Each is good for about 280 ohms Rs. For 6M, each multiple 2-turn choke through the 1-in i.d. solid or clamp-on core provides about 900 ohms Rs. Smaller diameter cores can be used if RG400 is used for the length of line needed for the choke.

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