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.


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



  • 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
    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.
    Within 2 days of publication, the Roxburgh RES5-F15 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 many more 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.


22 thoughts on “Clean Up Your Shack – 2019

  1. Peter

    Good day

    I attended the RSGB Convention and was pleased to be able to see your presentation on cleaning up the shack. I learnt a lot, and will be implementing many of your suggestions.

    Recently I had decided to renew my coax feeders, and bought some Messi and Paolini Ultraflex 7 to do this with. From the data sheet, the minimum advised curvature in multiple bends is 68mm, giving coax loop diameters of 136mm, which might be acceptable at the antenna feed-point, but would be somewhat cumbersome at the point where the feeder leaves the radio. I intend to use 2 stacked FT240-31 toroids for the choke formers. I wondered therefore if RG58 which can be encouraged to a smaller diameter would be suitable for the choke construction, or perhaps you would suggest I should invest in some of the thin Teflon coax. In either case, the choke for use at the radio end would have to have connectors at each end in order to ‘splice’ it into the feed line. I have always tried to avoid unnecessary connectors in the feedline as I understood they would be sources of potential problems. Is the benefit likely to outweigh any issues that an additional 2 connectors in the feedline might provoke? (Maximum feedline length is 45m)

    I usually work at 10W, with ocasional forays to 100w, and only rarely 400W. My location is semi-rural, and although I am not as plagued with nose as some of the recent correspondents to RadCom have indicated, anything to help seems to be a good idea. As I am making a change to my feeders, I would like to do the job just once, but properly.

    Thank you for your talk, and the links to the other aspects of the topic.



    1. GM3SEK Post author

      Hello Peter

      Glad that you enjoyed the talk, and I’m sorry it wasn’t possible to be there in person.

      At the power levels you normally use, I would be inclined to wind the chokes with RG58. It will allow you to wind more compact chokes and will also handle 400W for occasional use. Don’t worry too much about connectors – good connectors, correctly fitted and well waterproofed, should never be a problem.

      73 from Ian GM3SEK


  2. Alison

    Hi, I’m presently buying the components to make your mains filter, I understand why you’ve used a 31 and a pair 43’s however what about the lower frequencies? For complete coverage surely you should have a mix 75 / J in there somewhere as well? (I’m an avid LW / MW listener as well as the Ham bands). What do you think about half a dozen or so turns around a type 75 ring (or two of them, stacked) immediately after the twin 43’s? Thanks, Ali.


    1. GM3SEK Post author

      Hello Ali

      Thanks for your comments. The filter that I showed was optimized for 1.8-30MHz, and I have not considered any lower frequencies. However, from the mention of #75 mix I guess that you have already read K9YC’s paper on ‘Chokes and Isolation Transformers For Receiving Antennas’ [1], where Jim shows some common-mode chokes for MF antenna feedlines that can easily be wound on small #75 toroids using twisted pairs from CAT5 cable.


      The difficulty for a MF mains choke is the much larger wire diameter (three heavy wires twisted together) and the much smaller size of the available #75 cores – particularly the internal diameter through which the multiple turns of twisted wires must pass. On the positive side, extremely high choking impedances are probably not necessary for a mains choke because the prevailing system impedance is quite low. A possible candidate may be the 0475176451 snap-on core: if you reduce the size of the mains wire to 1.5mm^2 it may be possible to fit 4 or 5 turns through, which would give a useful choking impedance below 1MHz.

      Obviously haven’t tried this myself but would be interested in any results.

      73 from Ian GM3SEK


  3. Bernard

    Hello Ian
    Thanks for all the work you do make our hobby more rewarding. This may be a blindingly obvious question but where does the earth (green/yellow) wire go after it exits the large snap on? I can see that the live and neutral from the snap-on go to the commercial mains filter and also that all three wires from the mains go to the commercial filter. Many thanks, Bernard.


    1. GM3SEK Post author

      Hello Bernard,
      The earth wire from the unfiltered mains input and the earth wire going to the RF chokes both connect to the “E” tag on the metal body of the mains filter.


    1. Bernard

      Having now built the filter exactly as described I can report a huge improvement in noise levels (S7/8 to S3 on 40m and 80m). These lower bands were off limits to me in the past as far as SSB went and now they’re not. Couldn’t be happier! Many thanks Ian for the work you have put in to offer RFI/EMC solutions to the Amateur Radio community.


  4. Mike Naylor


    I wonder if it is acceptable to install the filters as part of a permanent installation? I am reluctant to ask my electrician to do this unless there is a precedent.. The reason for doing this is that more sockets could be protected by one filter.

    73 Mike G4CDF


    1. GM3SEK Post author


      I do not know the regulatory situation for a permanent installation, but it’s sure to be more restrictive than for a 13A extension.

      If you only need more sockets than the 6-way board shown in the photographs, double-row boards are available up to 10 ways – always provided that the total load does not exceed 13A. However, there are also several other factors that limit the current capacity of this mains filter to 13A, including the 3-core flex, the number of turns that can be passed through the centre of the ferrite cores, and the current rating of the packaged mains filter.

      Sorry that I can’t be more helpful.

      73 from Ian GM3SEK


      1. Mike G4CDF

        Ian, many thanks. I will follow your proven design as it is more flexible.
        I have also seen your slides on VHF/UHF baluns. Apart form the baluns at the antennas do you recommend any filters on the rigs or supplies?

        73 Mike G4CDF


      2. GM3SEK Post author

        Additional filters on commercial rigs should not normally be needed. ALL switchmode power supplies need filters on both input and output, but that topic is well covered elsewhere.

        73 from Ian GM3SEK


  5. davek0974

    Hi, i’ll be building the filter and have the parts on the way, thanks for all the research work here.

    I’ll also be bonding my equipment as outlined in the clean-up-your-shack video, but i’m unsure if the bonding plate/braid should be connected to the filtered mains earth point or not??

    Dave (awaiting callsign)


  6. GM3SEK Post author

    Yes, the mains earth connection on the shack side of the filter should be connected to the equipment bonding strip. That was mentioned in the 2015 talk, but I should have included it in the 2019 update as well.


  7. Pingback: Clean up your shack – Part 2 – M6RUG

  8. John

    Hi Ian
    Well thanks for all the info. I have just placed the order with Farrnell and CPC so hope to have the filter all built by weekend. I also ordered up the kit to build the CM Chokes as well. I dropped an email to your old blog posts if you can check thanks



  9. Dave M6RUG

    Hi Ian

    Quite simply, thank you!

    Your filter design is working a treat on 20m and above with 3-4 S points of noise gone! 40/30 just 1 S point.

    I did not manage to twist the wires together successfully and still get 7 turns so ended up with them flat.


    Dave (M6RUG


  10. John

    Hi Ian,

    Looking forward to building one of these. Any differences when dealing with 110VAC as opposed to 220?




    1. GM3SEK Post author

      Hi John,

      Two differences that I can think of, compared with 220/230V:

      1. All AC supply currents will be multiplied by about 2. The practical limitation will be the current/temperature ratings of the twisted wires that you use for winding the chokes.

      2. Also be careful about the ratings of the packaged mains filter (sorry, I have no experience about 110V AC).

      73 from Ian GM3SEK



Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s