The next time you get a new device and excitedly take apart its plastic-wrapped small power supply, remember this: For every switch-mode power supply you plug in, amateur radio operators will shed tears. Noisy, broadband, tears full of harmonics.

The degree of interference from this fact to you depends on which side of the microphone you are on, but radio frequency interference or RFI is at least we should be aware of. [Josh (KI6NAZ)] is keenly aware of the RFI in his ham shed, but instead of cursing the rising background noise, he proposes some useful techniques to find and eliminate it-or at least reduce its impact .

To solve the problem, we must first locate the source of the RFI. For this reason, [Josh] used the classic "one circuit at a time" method-kill each circuit breaker in the panel, and monitor the noise floor while reopening each circuit breaker . This should at least give you a rough idea of ​​the location of the problematic device in your home. From there, [Josh] uses a small shortwave receiver to locate problem areas such as refrigerators, clothes dryers, and his cabin computer. Facts have proved that home flat-screen TVs are also very noisy. Remedial techniques include winding each power cord and cable around a toroidal coil or sandwiching a ferrite core around them, whether on offending equipment or in a shed. He even added a line filter to the dryer to suppress unnecessary interference.

Judging from his waterfall display, [Josh]’s efforts paid off, reducing his background noise from S5 to around S1. Too bad, he had to deal with things himself-after all, it's not like the FCC and other spectrum regulators don't know that there is a problem.

Gary Johnson NA6O gave a wonderful talk about RFI hunting at Pacificon http://wb9jps.com/Gary_Johnson/RFI.html

This is a good document Find and Killing Receive Noise. My speech at the Ham Club: Finding_Noise_NA6O.pdf

In order to find this document, you seem to be missing the key part of the URL.

Scroll down on the page with the first link http://wb9jps.com/Gary_Johnson/RFI.html to find the link to the pdf document. The link is not copied correctly

Then you live in a busy city surrounded by other houses...like a high-end audio freak living in the flight path of an airport...you have come to the wrong place

Not all of us have the opportunity to move to the top of a remote mountain.

Maybe they should rename their recent article "Spend a day on top of a mountain with a Yagi trekking pole"

Oops, lifting the ground on the dryer may not be a good idea. Personally, moving the ground to the ground input would be a better idea.

I totally agree. The grounding of the plug and socket should be connected to a single grounding point of the filter. This is a safety issue!

Agree, it is definitely a bad idea.

Reason: If a malfunction occurs, you may get an electric shock.

If it does so, will it increase the data transfer rate of homeplug? :-)

If you don't care about RFI, there is at least 15dB of available power in most Homeplug devices for logging in and increasing it.

Save it for later. It's time to figure out whether that high-pitched buzzing is the RF I suspect or myself.

I found what I thought was my high-pitched hum (and found some on me, not just resonating on other aluminum objects during inspection) using only the sound card and Mini-3 Bat detector, I found It's not me.

It's really simple...Although ideally, a higher quality low-noise background USB sound card with a 192kHz sampling rate and some noise-reducing mods help to open the view, such as Spectrum Lab or other free spectrum analyzer software: http ://www.vlf. It/pernter1/x-fi_modifications.html

Behringer umc202hd is another sound card I invested in, and eventually I want to make a portable case with SBC or a streamlined laptop.

Recently, I have been considering investing in a 384kHz SB G6 so that I can better view frequencies up to 192kHz without aliasing.

Finally, I started reading again in winter where I stopped using the sensor system to reach above 100kHz (using Panasonic WM-61A with a frequency lower than 100kHz) and use some broadband transducers, I guess unless I can modify it to prefer this design Final thoughts: https://www.youtube.com/watch?v=quuHV9pTyoo

Of course... because all of these are not thick hardware and thin or no firmware... there is a latency problem, which is interesting compared to a superheterodyne scanner or receiver.

Great article topic. We definitely need more RFI hunter radio direction finding, because in the future, for a few people, wireless performance will not decrease.

If you really want to delve into this topic, please check out this article by Chuck in 2006, W1HIS: http://www.yccc.org/Articles/W1HIS/CommonModeChokesW1HIS2006Apr06.pdf. I believe that when Chuck writes this article, his QTH is a small city.

Good article, thanks for the tip of AI6XG

Yes, the fastest way to check it is to cut off the power and run the device on battery. I did it. The noise is the same. game over. I can kill my radio as I want, but I can't kill my neighbor's electrical appliances.

Don't give up so quickly. You can use different types of antennas. Magnetic rings tend to pick up less RFI. You may even encounter problems inside the radio, causing the noise floor to be too high. Take your radio to another location and see how it performs. Check to make sure you have a good ground.

I worked as a "transmission technical support engineer" for the New York Telephone Company for several years, making a living in pursuit of noise (RF and VF). Happily, all the super test equipment are within easy reach. Then I was promoted to Bellcore and ended teaching on noise mitigation and grounding, and even better resources.

This is good information, but breaking ground is not a good idea.

Many modern refrigerators have "inverter" compressors that run continuously, rather than running only when needed, as in old refrigerators. If it was me, and I had already done so, I would contact the manufacturer of any RFI-producing device via phone and email to remind them of their obligations under FCC rules and regulations.

Is your dryer a gas dryer?

In my previous reincarnations, I have served as a corporate domain expert in the electromagnetic compatibility field for about 17 years. Not only does it comply with FCC and EN compliance, but also involves all kinds of electromagnetic problems you can think of-crosstalk, power system noise, ESD, magnetic field sensitivity In tapes and disk drives, and even occasionally magnetoacoustic problems-almost all electromagnetic problems known to mankind. In my opinion, the FCC can always find reasons to turn a blind eye to the spectrum noise impact of any new technology that promises to make certain companies or other companies profitable, and HAM radio and radio astronomy seem to be very low on their lists. Services to protect-therefore power line communications and other new sources of noise. A good general rule of thumb I found is that if the problem is lower than 200MHz, the radiation mechanism is more likely to involve radiation from external cables. Look for slot radiators and cavity resonance effects above 200MHz. In the next 20 years of my career, I finally got rid of this industry, specializing in signal integrity and high-speed circuit design-in the laboratory trying to analyze the dilemma of new products reduced a lot of time to ship PDQ to meet revenue forecasts -And the pressure is much less :-).

What if my circuit board is part of my radio? I can’t wrap the circuit board on my ferrite ring, nor can I remove my radio, because that’s the point! filter?

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