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My neighbor has indicated that they can hear noise from their computer amplified speakers when I'm transmitting. We've done a few tests and it does appear that it's my transmitter that's causing the noise.

I've performed some testing and determined that I'm well within my operating limits. The transmissions are clean, within power limits, etc. There is nothing I can do on my end to resolve the problem, other than cease transmission.

My neighbor is unwilling to replace his speakers with a more noise resistant set, though he may be willing to allow minor modifications if it doesn't otherwise affect performance.

What should I try that should help remove, or at least reduce, the noise on the speakers?

Kevin Reid AG6YO
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Adam Davis
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  • What kind of an antenna do you have? – PearsonArtPhoto Dec 11 '13 at 15:59
  • I haven't determined if the noise depends on the band or antenna being used, so for the moment I'd like to avoid antenna or band specific solutions. – Adam Davis Dec 11 '13 at 16:33
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    Depending on the antenna, especially weird ones like OCF antennas, it could be a sign of reflected power getting somewhere it shouldn't, which is why I ask the question. Still, there's a lot that's not antenna specific, but it's worth mentioning at least... – PearsonArtPhoto Dec 11 '13 at 16:39
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    I had a neighbor receiving me on his electric guitar amplifier. It turned out we shared the same power line transformer, and the power lines to his house were parallel to my antenna. Radio Shack had chokes for extension cords, I bought some for him and all was well. – Optionparty Jan 19 '14 at 01:26

3 Answers3

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Wikipedia writes to say

By the regulation, the FCC DoC certification mark is mandatory for devices classified under part 15 (IT equipment like computers, switched-mode power supplies, monitors etc., television receivers, cable system devices, low-power transmitters, un-licensed personal communication devices) and part 18 (industrial, scientific, and medical (ISM) devices that emit RF radiation) of the FCC regulations.

The subject is covered in some depth on hamuniverse.com which writes to say (free-form edit applied by me)

Rectification and overload are both problems with the design of the affected equipment, and after decades of investigation, the FCC knows this.

In your case, the issue & onus lies upon the manufacturer of the equipment experiencing interference.

Having made that clear to the neighbour, you might try introducing a low-pass filter (also mentioned in the article on hamuniverse referenced above)

Another alternative (+: dump a load of ferrite beads over their speaker cables. More detailed reading is listed at this site

VU2NHW
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    Another excellent paper on RFI mitigation can be found here: http://www.yccc.org/Articles/W1HIS/CommonModeChokesW1HIS2006Apr06.pdf. While the legal onus may be on the manufacturer, that stance won't make any friends in your neighborhood. Explore some of these techniques, see what works and introduce them to your neighbor. – WPrecht Dec 11 '13 at 17:07
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    @WPrecht-AB3RY: Concurred. At the same time there _is_ the possibility of offering the neighbour a hand, and his taking an ell. We've probably all heard about the ham who offered to assist one neighbour with RFI issues, and was taken to task by another who said he never experienced termite issues _until_ that antenna appeared in the neighbourhood! – VU2NHW Dec 11 '13 at 17:14
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I disagree with part of the answer given by VU2NHW:

In your case, the issue & onus lies upon the manufacturer of the equipment experiencing interference.

This is not what the FCC regulations say (assuming we are talking about US jurisdiction). Part 15 clearly puts the issue in the hands of the consumer. The only recourse the consumer has with the manufacturer is through tort law, not federal regulations. However, the consumer can use part 15 to help qualify them as an aggrieved party to allow tort proceedings if the consumer chooses to pursue this course.

There is also case law that reasonably blocks a neighbor ftom attempting tort actions against the ham. This may not stop a filing necessarily, but it should normally bring the matter to a swift and favorable conclusion for the ham.

In these situations of neighbor complaints, the ham is advised to make sure their signal is clean (spectrum analyzer screen shots) and that they have conducted and logged any necessary RF exposure assessments. Keeping a basic log showing the time going on and off the air, the band, mode, and output power is also helpful. If the FCC then makes an inquiry, the ham can show sound due diligence and will be exonerated by the FCC. The FCC will then send a brochure and letter to the consumer advising them that the ham is operating legally and the problem is with the consumer's electronics.

We all want to be good neighbors and help them with their interference problems. But before getting out your toroids and tools, carefully consider the litigious conditions that surround us and weigh this in your decision as to what course of action you will take.

Edit:

Computer speakers are notorious for being affected by nearby EM energy. The most effective remediation is the application of toroid cores on the speaker and power leads to the speaker boxes. Depending on the length of the wires, a toroid on each end of the wire may be warranted. Toroid cores of type 31 material are generally the most effective. Get large enough cores to allow connectors to pass through the hole in the center. Make multiple turns of cable on each core as the EM choking goes up as the number of turns squared.

Glenn W9IQ
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  • Don't help your neighbors, because they might sue you? Seriously? – Phil Frost - W8II Jul 10 '17 at 14:33
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    @philfrost-w8ii I am not sure how you read "We all want to be good neighbors and help them" and "weigh this" to translate to not helping your neighbor. That certainly wasn't my intent - the point is know your limitations and don't get blind sided. – Glenn W9IQ Jul 10 '17 at 15:10
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    Some comments have been deleted. Please remember that comments are for discussing improvements to questions and answers. If the discussion becomes about the general topic rather than the particular answer, then it should be taken to [meta] or [chat] as appropriate, and language should be kept respectful. – Kevin Reid AG6YO Jul 10 '17 at 23:14
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I have this hunch that using a standard Cat-5e networking cable to replace the speaker wires would work because wikipedia Twisted-pair says:

twisted pair reduces electromagnetic radiation from the pair and crosstalk between neighboring pairs and improves rejection of external electromagnetic interference.

Also, instead of just using one pair, you could use all of them in parallel for better conductivity. An additional benefit is, if one wire breaks, the others remain.

The last sentence in this section on Unshielded-twisted-pair (UTP) at Wikipedia says a balun is needed, though. Still learning about that... Would this application require a balun?

MicroservicesOnDDD
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