Category Archives: Antennas, Baluns and EMC

Clean Up Your Shack – 2019

The online follow-up to my talk for the 2019 RSGB Convention.

3 chokes

What’s new since 2015

  • Choke Chart and RadCom Plus article by Steve Hunt G3TXQ (SK)see separate blog entry below
  • Revised Choke Cookbook by Jim Brown K9YC
  • Large Fair-Rite #31 core
    These are a game changer!  
    See ordering details below.

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  • Constant changes in the prices of ferrite cores (but still the same Best Buy supplier)
  • Updated Whole-Shack Mains Filter

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Downloads

  • Extended slide pack (PowerPoint) includes more slides showing how to build the updated Whole-Shack Mains Filter.
  • View ‘Clean Up Your Shack 2015’ (YouTube) for more detailed background.
  • Slides from my 2010 talk about chokes and baluns  to drill deeper into that subject.

Fair-Rite 0431177081 snap-on core

Not cheap, but well worth it. If RF noise threatens to take your hobby away, then surely it’s worth something to get it back?

  • Manufacturer’s data  Ignore the photograph – this biggest bead doesn’t look like that.
  • Current Best Buy supplier – and always near the top of the list –  is www.mouser.co.uk
    Again, ignore the photograph, trust the part number.
    Notice the big price break at quantity 10. This makes an ideal club purchase.
    UK prices are in GB£ but do not include VAT. However, that is all you have to pay. Three-day FedEx shipping from the USA is streamlined and free for orders over £50+VAT.

Parts list for the Whole-Shack Mains Filter

  • Packaged 15A or 16A mains filter, single phase, 250VAC rated.
    UPDATED Within 2 days of publication, the Roxburgh RES5-15 filter from Farnell was sold out! The specific type of mains filter is not critical, so instead let’s try the Schaffner FN2030-16-06 (also from Farnell, but currently over 3000 in stock).
  • Large Fair-Rite core 0431177081: Mouser (see above) or Farnell
  • Qty 2, Fair-Rite oval core 2643167851: Mouser or Farnell
  • Plastic box CE-TEK GR17012 to fit the above parts: CPC  EN84544
  • Qty 2, plastic cable glands, 5-10mm size: CPC CBBR7352
  • At least 3m of 3-core 2.5mm² mains flex, 90ºC rated: eBay, eg here
  • 13A socket strips to meet your requirements
  • 13A plugThe maximum total current supplied to all sockets is 13A, limited by this plug.

 

Steve Hunt, G3TXQ – In Memoriam

New Year’s Morning, 2019

G3TXQ was well known and respected throughout the technical world of Amateur Radio, through his website and countless postings to a wide range of groups and mailing lists. Always meticulous and deep-thinking, Steve was a fount of good information – and also a very nice guy.

Steve passed away peacefully on 30th December 2018 after a long battle with cancer, which he also recorded in that same meticulous manner.

G3TXQ is known particularly for his optimized versions of the Cobweb and Hexbeam antennas, and for his work on common-mode chokes. His website karinya.net is already archived at https://web.archive.org/web/20180428131952/http://karinya.net/
and if you haven’t already visited, I strongly recommend it. Take the tour, and you will meet the man he was.

Common Mode RF Chokes

G3TXQ-X

In addition to the material on his website about common-mode chokes, in 2015 Steve wrote a stand-alone article for RSGB’s online technical magazine RadCom Plus.  That article is in danger of falling into obscurity, taking with it some new information that has not been published anywhere else, so I am archiving it here in memory of Steve:

Common Mode Chokes: G3TXQ 2015

The article included a new version of Steve’s famous graphic to help in selecting broadband ferrite chokes to cover various HF amateur bands. The best chokes are the ones that cover the required band(s) with both the dark green shading and the black underline. Orange and red shading are to be avoided – the choke may do some good, but may also have problems. (For clarity, I have added a large ‘X‘ across the three chokes at the bottom. As Steve explains, those were included as particularly BAD examples, NOT to be copied.)

Writing this is not the way I had hoped to begin a New Year.
RIP, Steve.

 

VHF-UHF Baluns

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

Update: RSGB have now released the video at https://thersgb.org/members/resources/?id=5762 (member login required; it will probably be several more months before the video is transferred to YouTube).

I always cringe to hear myself talking, but the sound track does add some context to the previously released slide pack ( still available here ).

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