{"id":48313,"date":"2021-03-30T07:50:01","date_gmt":"2021-03-30T11:50:01","guid":{"rendered":"https:\/\/swling.com\/blog\/?p=48313"},"modified":"2021-03-30T07:50:01","modified_gmt":"2021-03-30T11:50:01","slug":"guest-post-indoor-noise-and-ferrites-part1","status":"publish","type":"post","link":"https:\/\/swling.com\/blog\/2021\/03\/guest-post-indoor-noise-and-ferrites-part1\/","title":{"rendered":"Guest Post: Indoor Noise and Ferrites, Part1"},"content":{"rendered":"

\"\"<\/a>Many thanks to SWLing Post<\/em> contributor, TomL<\/a>, who shares the following guest post:<\/strong><\/p>\n

\n

Indoor Noise and Ferrites, Part 1<\/h1>\n

by TomL<\/strong><\/p>\n

My magnet wire loop antenna<\/a> on the porch reminded me to revisit aspects about my noisy Condo that I still needed to understand.\u00a0 Some RF noise I could control if I could find the right kind of information that is understandable to a non-engineer like me.\u00a0 There is a lot written about the general problem of noise and radio listening, for instance this ARRL article with web links to research \u2013 www.arrl.org\/radio-frequency-interference-rfi<\/a>, but I needed to get more specific about my particular environment.<\/p>\n

I had tried some common clamp-on TDK ferrites I had obtained from eBay a long time ago but they only seemed to work a little bit.\u00a0 I have since found out these are probably the ones which are widely used on home stereo system connections used to reduce noise on those systems.\u00a0 There must be a better way.<\/p>\n

The more I researched topics, like a portable \u201cLoop on Ground\u201d antenna<\/a>, or, using RF chokes on the magnet wire loop, it dawned on my feeble, misguided brain that I was wrongly thinking about how to use ferrite material.\u00a0 For one thing, the material used to suppress RF noise is made with a certain \u201cmix\u201d of elements, like Manganese-Zinc, that electrically \u201cresists\u201d a specified frequency range.\u00a0 Fair-Rite has a useful Material Data Sheets web page<\/a> which lists the Types of ferrite material.\u00a0 For dealing with noise (at the Source causing the problem), I needed to use the right kind of \u201cSuppression\u201d materials and proper placement.\u00a0 So, it (partly) made sense why the TDK snap-on ferrites might not fully work to reduce certain noise coming from my computer screens, LED lights, USB devices, and cheap Chinese-made power adapters.<\/p>\n

A very good\u00a0 paper is by Jim Brown (K9YC) of Audio Systems Group entitled, \u201cUnderstanding How Ferrites Can Prevent and Eliminate RF Interference to Audio Systems [PDF]<\/a>\u201d.\u00a0 There is a longer paper speaking directly to Amateur Radio folks<\/a>, but the Audio version is simpler and it uses some of the same\u00a0 graphs and ideas.\u00a0 I was drawn to the very detailed Impedance measurements of many different \u201cTypes\u201d of ferrite material used for different noise mitigation.\u00a0 I remember the traumatic pain of my college experience trying mightily to understand the Van Vlack Materials Science text book to no avail.\u00a0 But Jim’s paper reminded me of the importance of using the correct type of ferrite material and in an optimal way that reacts favorably in the target frequency range to solve a particular noise problem.\u00a0 So, what are my problem areas?<\/p>\n

Shortwave Noise<\/b><\/h2>\n

Loop antennas have been what I have experimented with the most.\u00a0 They do not pick up as much man-made noise (QRM) and they have a space saving footprint.\u00a0 Fortunately, there is a wooden porch where these things have been tried.\u00a0 I had successfully built a broadband amplified \u201cferrite sleeve loop\u201d (FSL) in the past.\u00a0 It was useful for a while but it fell into disrepair and also the Condo building has steadily increased in noise output.\u00a0 The amplifier was just amplifying the noise after a while.\u00a0 I also tried phasing two antennas but found the ever increasing noise cloud was coming from all directions and I could not null it out.\u00a0 I even tried a \u201cmini-whip\u201d from eBay but that just produced a wall of noise.<\/p>\n

I recently tested AirSpy’s YouLoop written about before<\/a>, and the results were good.\u00a0 However, it seemed obvious to me that it was too small as a passive loop to capture shortwave signals strongly enough without resorting to another amplifier attached at the antenna and would not improve the signal\/noise ratio.\u00a0 My current solution is a unamplified stealth magnet wire loop about 32 feet in circumference.\u00a0 In that article<\/a>, I mention things like common mode RF chokes at both ends of the antenna connection, horizontal polarization, and basically accepting that only the stronger shortwave signals will be received in a predictable manner.\u00a0 I think for now, this is about all I can do for shortwave and mediumwave noise, as far as my own Condo-generated noise. Neighborhood noise is a different topic.<\/p>\n

VHF Noise<\/b><\/h2>\n

I then started to isolate which devices caused which kind of noise when listening to my outside amplified antennas for FM\/VHF and UHF-TV transmissions.\u00a0 Many consumer Power adapters make a lot of noise from VLF up into UHF ranges.\u00a0 One thing I did right was to try a 10 pack of these little miracle \u201cWall Wart\u201d toroids from Palomar Engineers<\/a>.\u00a0 One by one, I put one of these small toroids (19mm inside diameter) on my home AC adapters as shown in the pictures, and the noises started disappearing.\u00a0 It does not explicitly say, but I believe it is Type 75 material which suppresses the noise generating AC adapter (at very low frequencies) when wrapped 8 \u2013 12 times.<\/p>\n

\"\"<\/a><\/p>\n

Most egregious of these was my CCrane FM2 transmitter<\/a>.\u00a0 A strangled warbling sound kept emanating from the monitor closest to my laptop. Installing ferrites on the laptop and back of the monitor were not working.\u00a0 I moved the FM Transmitter and noticed a reduction in noise.\u00a0 So, I put one of these little toroids on the power input of the device and the noise disappeared.\u00a0 Apparently, it was picking up noise from the monitor (as well as its own power adapter) and rebroadcasting it to all my other radios!\u00a0 The strangled warbler is no more, I choked it (HaHa, sick bird joke).<\/p>\n

While looking for the monitor noise, I put the eBay TDK ferrites on all the USB ports and HDMI ports.\u00a0 This has helped greatly on VHF and confirms my suspicion that these cheap TDK ferrites are indeed a common type of ferrite material.\u00a0 Some informative graphs can be seen in Jim Brown’s Audio paper mentioned before.\u00a0 One example might be Figure 22, which shows the #61 Series Resistance which peaks around 100 MHz when using a toroid with three \u201cTurns\u201d.\u00a0 More confused, I could not find a definition of a \u201cTurn\u201d.\u00a0 Eventually, in his longer paper to Amateur Radio operators, he defines it, \u201c…is one more than the number of turns external to the cores\u201d.\u00a0 Somewhere else he describes using many single snap-on ferrites being electrically equal to just one toroidal ferrite with multiple Turns.\u00a0 And interestingly, more Turns shifts the peak impedance substantially lower in frequency.\u00a0 So, using the graphs he supplies, one can target a noisy frequency range to try to suppress.<\/p>\n

I then put 6 of the TDK ferrites on the VHF input to the AirSpy HF+.\u00a0 Some FM grunge was reduced and was thankful for that.\u00a0 The rest of the background noise truly seems to be coming from the outside picked up by the amplified antenna.<\/p>\n

Also, I juggled a couple of the amplifiers around and now have separate VHF\/FM and UHF\/TV amplifiers which cleaned up the FM reception a little bit more – https:\/\/www.youtube.com\/watch?v=zkDsy95et2w<\/a> .<\/p>\n

UHF TV Quality<\/b><\/h2>\n

On a whim, I put the balance of the TDK ferrites on the FM\/TV splitter input cable, 10 in all.\u00a0 The FM reception did not improve but the Over The Air UHF TV reception Quality improved noticeably.\u00a0 My weakest TV station now has a stable Signal level and the Quality is pegged at 100%.\u00a0 This is a nice surprise since it means that now all local TV stations on UHF will come in cleanly without dropouts and I can view all digital subchannels.\u00a0 I was even able to rescan and added two more low-power stations never seen before. ?<\/p>\n

\"\"<\/a><\/p>\n

\"\"<\/a><\/p>\n

LED lights<\/b><\/h2>\n

I have common LED lights hanging over a number of fish tanks and some grow lights over an indoor plant box and can hear this noise on upper shortwave and higher radio bands.\u00a0 In a future article, I will explore RF noise from lights as its own special topic. For instance, why do some LED lights generate RFI and how to know before buying (I am using BR30 spot bulbs from name brands)?\u00a0 Also, there is a new kind of LED \u201cfilament\u201d light out now that uses much smaller LED’s on both sides of an aluminum strip, greatly reducing electromagnetic noise output (or do they??).\u00a0 More questions than answers.<\/p>\n

I will explore creating my own customized AC power cord attached to the AC power strips of the LED lights.\u00a0 I will need to test this for safety and efficacy, so I will want to take some time to do this right.\u00a0 The hope is that, using Jim’s info, I will be able to create a broad spectrum RFI suppression AC power cord and cost less than $30 each cord.\u00a0 We’ll see.<\/p>\n

Finally, I will look at \u201cstacked\u201d toroids using different mixes of ferrite Types, creating a custom RF suppression better than using just one Type of ferrite material, using AC cords as the main examples. For instance, the best set of graphs in Jim’s paper, in my opinion, are Figures 21 and 24 compared to each other.\u00a0 Something I did not know before is that one can not only use multiple turns on a single toroid to get a lower, peaked frequency response, but also stack multiple toroids of the same Type to get a smoother frequency response.\u00a0 Then on top of this, combine that set with other Types to create a customized frequency response curve.<\/p>\n

Radios are quieter now.\u00a0 Those pesky grow lights are still a problem as well as the upstairs neighbor’s lights which seem to be on a timer, making FM reception noisy again after 5pm!<\/p>\n","protected":false},"excerpt":{"rendered":"

Many thanks to SWLing Post contributor, TomL, who shares the following guest post: Indoor Noise and Ferrites, Part 1 by TomL My magnet wire loop antenna on the porch reminded me to revisit aspects about my noisy Condo that I still needed to understand.\u00a0 Some RF noise I could control if I could find the […]<\/p>\n","protected":false},"author":15,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2}},"categories":[8,3194,545,627,3,196,43,1113],"tags":[9222,3324,4089,2651,1296,453,3841,5119],"class_list":["post-48313","post","type-post","status-publish","format-standard","hentry","category-articles","category-guest-posts","category-ham-radio","category-how-to","category-news","category-qrm","category-shortwave-radio","category-tutorials","tag-ferrite-chokes-rfi","tag-fighting-qrm","tag-qrm","tag-radio-frequency-interference","tag-rf-noise","tag-rfi","tag-switching-power-supply-noise","tag-toml"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_shortlink":"https:\/\/wp.me\/pn3uc-czf","jetpack-related-posts":[{"id":19251,"url":"https:\/\/swling.com\/blog\/2016\/06\/guest-post-my-evolving-morphing-sw-listening-station\/","url_meta":{"origin":48313,"position":0},"title":"Guest Post: My Evolving, Morphing, SW Listening Station","author":"Thomas","date":"June 5, 2016","format":false,"excerpt":"Many thanks to SWLing Post contributor, TomL, for the following guest post: My Evolving, Morphing, SW Listening Station by\u00a0TomL, May 26, 2016 My interest in radio listening has been rekindled after a long hiatus in parallel to my dwindling interest in Mainstream Media.\u00a0 It is now about 8 years without\u2026","rel":"","context":"In "AM"","block_context":{"text":"AM","link":"https:\/\/swling.com\/blog\/category\/am\/"},"img":{"alt_text":"Sony-2010","src":"https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2016\/05\/Sony-2010-1024x632.jpg?resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2016\/05\/Sony-2010-1024x632.jpg?resize=350%2C200 1x, https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2016\/05\/Sony-2010-1024x632.jpg?resize=525%2C300 1.5x"},"classes":[]},{"id":21870,"url":"https:\/\/swling.com\/blog\/2016\/10\/guest-post-more-anti-noise-ideas\/","url_meta":{"origin":48313,"position":1},"title":"Guest Post: More Anti-Noise Ideas","author":"Thomas","date":"October 24, 2016","format":false,"excerpt":"In a previous guest post, SWLing Post contributor TomL, shared his \"Evolving, Morphing, SW Listening Station\"\u00a0where he detailed the many ways he's trying to fight heavy radio interference at his listening post. The following post is TomL's update: More Anti-Noise Ideas (Continuing the hunt for better reception in a foul\u2026","rel":"","context":"In "AM"","block_context":{"text":"AM","link":"https:\/\/swling.com\/blog\/category\/am\/"},"img":{"alt_text":"toml-radios","src":"https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2016\/10\/TomL-Radios.jpg?resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2016\/10\/TomL-Radios.jpg?resize=350%2C200 1x, https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2016\/10\/TomL-Radios.jpg?resize=525%2C300 1.5x, https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2016\/10\/TomL-Radios.jpg?resize=700%2C400 2x"},"classes":[]},{"id":47496,"url":"https:\/\/swling.com\/blog\/2021\/01\/build-an-affordable-but-stealthy-magnet-wire-vertical-loop-antenna-to-mitigate-condo-qrm\/","url_meta":{"origin":48313,"position":2},"title":"Build an affordable (but stealthy) Magnet Wire Vertical Loop antenna to mitigate condo QRM","author":"Thomas","date":"January 28, 2021","format":false,"excerpt":"Many thanks to SWLing Post contributor,\u00a0TomL, who shares the following guest post: Magnet Wire Vertical Loop Antenna by TomL For those of you in a noisy condo like me, the environment does not give me many options.\u00a0 I was experimenting with a YouLoop on the wooden porch with somewhat acceptable\u2026","rel":"","context":"In "Antennas"","block_context":{"text":"Antennas","link":"https:\/\/swling.com\/blog\/category\/antennas\/"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2021\/01\/MagnetWireVerticalLoop.jpg?resize=350%2C200&ssl=1","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2021\/01\/MagnetWireVerticalLoop.jpg?resize=350%2C200&ssl=1 1x, https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2021\/01\/MagnetWireVerticalLoop.jpg?resize=525%2C300&ssl=1 1.5x, https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2021\/01\/MagnetWireVerticalLoop.jpg?resize=700%2C400&ssl=1 2x"},"classes":[]},{"id":30672,"url":"https:\/\/swling.com\/blog\/2018\/02\/indoor-shortwave-antenna-options-to-pair-with-a-new-sdr\/","url_meta":{"origin":48313,"position":3},"title":"Indoor shortwave antenna options to pair with a new SDR","author":"Thomas","date":"February 9, 2018","format":false,"excerpt":"Many thanks to SWLing Post contributor, Chris Freitas, who writes: \"I am thinking of the new RSP1A SDR. Would you know of a good indoor antenna that would work well with it?\" Your antenna question is simple, but the answer is complex! First off, I think the RSP1A is a\u2026","rel":"","context":"In "Antennas"","block_context":{"text":"Antennas","link":"https:\/\/swling.com\/blog\/category\/antennas\/"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2017\/11\/RSP1A1-1024x708.jpg?resize=350%2C200&ssl=1","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2017\/11\/RSP1A1-1024x708.jpg?resize=350%2C200&ssl=1 1x, https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2017\/11\/RSP1A1-1024x708.jpg?resize=525%2C300&ssl=1 1.5x, https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2017\/11\/RSP1A1-1024x708.jpg?resize=700%2C400&ssl=1 2x"},"classes":[]},{"id":45481,"url":"https:\/\/swling.com\/blog\/2020\/09\/post-storm-power-outage-leads-emilio-to-find-the-rfi-spewing-source-of-his-problems\/","url_meta":{"origin":48313,"position":4},"title":"Post-storm power outage leads Emilio to find the RFI-spewing source of his problems","author":"Thomas","date":"September 20, 2020","format":false,"excerpt":"Many thanks to SWling Post contributor, Emilio Ruiz, who shares the following guest post: Apprehending an RFI-generating monster! At the beginning of the year, I was sad because, at home, an awful RFI noise appeared. The next few months the noise increase until S9!!. Day and night my receivers and\u2026","rel":"","context":"In "Guest Posts"","block_context":{"text":"Guest Posts","link":"https:\/\/swling.com\/blog\/category\/guest-posts\/"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2020\/09\/rfi-mitzu-power-supply-3-scaled-e1600610634110.jpg?resize=350%2C200&ssl=1","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2020\/09\/rfi-mitzu-power-supply-3-scaled-e1600610634110.jpg?resize=350%2C200&ssl=1 1x, https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2020\/09\/rfi-mitzu-power-supply-3-scaled-e1600610634110.jpg?resize=525%2C300&ssl=1 1.5x, https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2020\/09\/rfi-mitzu-power-supply-3-scaled-e1600610634110.jpg?resize=700%2C400&ssl=1 2x"},"classes":[]},{"id":62311,"url":"https:\/\/swling.com\/blog\/2025\/03\/radio-world-nrsc-studies-rf-noise-on-various-roadway-types\/","url_meta":{"origin":48313,"position":5},"title":"Radio World: NRSC Studies RF Noise on Various Roadway Types","author":"Thomas","date":"March 9, 2025","format":false,"excerpt":"Many thanks to SWLing Post contributor, Dennis Dure, who shares the following item from Radio World: NRSC Studies RF Noise on Various Roadway Types (Radio World) Radio World asked Cris Alexander to read the report and comment The National Radio Systems Committee recently published the results of a study on\u2026","rel":"","context":"In "News"","block_context":{"text":"News","link":"https:\/\/swling.com\/blog\/category\/news\/"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2025\/03\/2025-03-09-at-07.14.04.png?resize=350%2C200&ssl=1","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2025\/03\/2025-03-09-at-07.14.04.png?resize=350%2C200&ssl=1 1x, https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2025\/03\/2025-03-09-at-07.14.04.png?resize=525%2C300&ssl=1 1.5x, https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2025\/03\/2025-03-09-at-07.14.04.png?resize=700%2C400&ssl=1 2x"},"classes":[]}],"jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/swling.com\/blog\/wp-json\/wp\/v2\/posts\/48313","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/swling.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/swling.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/swling.com\/blog\/wp-json\/wp\/v2\/users\/15"}],"replies":[{"embeddable":true,"href":"https:\/\/swling.com\/blog\/wp-json\/wp\/v2\/comments?post=48313"}],"version-history":[{"count":0,"href":"https:\/\/swling.com\/blog\/wp-json\/wp\/v2\/posts\/48313\/revisions"}],"wp:attachment":[{"href":"https:\/\/swling.com\/blog\/wp-json\/wp\/v2\/media?parent=48313"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/swling.com\/blog\/wp-json\/wp\/v2\/categories?post=48313"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/swling.com\/blog\/wp-json\/wp\/v2\/tags?post=48313"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}