Sources of Noise on the HF Bands (read the description)

The noise floor has gradually gotten worse in recent decades, due to the introduction of more and more man-made electronic devices. And this adds to the noise floor generated in the receiver itself.
Radio receivers already have an inherent noise floor. One source of noise is due to the the heat generated by receiver components. This cannot be avoided. Another source of noise, predominant in superheterodyne receivers, is caused by something called phase jitter, a phenomenon associated with oscillators. The resultant noise is called phase noise. Newer technology has minimized the noise generated by such sources.
With a traditional superheterodyne receiver, each conversion stage adds more selectivity, but simultaneously each stage adds more phase noise. There receivers with three-stage (triple-conversion) and four-stage (quad-conversion) receivers. So we must choose whether to hear the weakest signals (sensitivity) or be able to block stronger unwanted signals (selectivity). Life is all about trade-offs isn’t it? Even with radios.
A brief history of receiver design:
Some radios in the past featured a preselector to help with selectivity, so a 2-stage (dual-conversion superheterodyne) receive architecture would deliver the sensitivity, while the preselector delivered selectivity. The preselector would allow the operator to favor a particular portion of the band they were tuned to. But the Preselector added cost. Note that a few transceivers on the market today include a preselector. FTdx5000MP, FTdx101D, FTdx101MP, TS-990S, IC-7610, are a few that include a type of preselector.
An IF (Intermediate Frequency) filter, often called a “roofing filter”, could be used, immediately following the 1st mixer, to add additional selectivity to the receiver’s first stage. Roofing filters are only available at specific frequencies so the 1st LO (Local Oscillator) must operate at a frequency that mixes with the incoming signal from the antenna to create a resultant 1st IF that matches the operating frequency of the roofing filter.
Higher quality roofing filters are available at lower cost if the receiver uses a down-conversion architecture. Down-conversion was in common use until the late 1970s. Down-conversion uses a 1st IF that is generally between 8 and 11 MHz.
To save the cost of a preselector, and to keep the 1st IF from preventing full receive coverage from 1.8 to 30 MHz, manufacturers switched to up-conversion, in the late 1970s. This placed the 1st IF at 40 to 70 MHz. The trade-off was the roofing filters. Roofing filters at 40 to 70 MHz are more costly and less effective.
In 2003, Ten-Tec introduced the Orion HF transceiver. The Orion reintroduced down-conversion and high-quality roofing filters. Yaesu would follow next, with the FTdx5000. Kenwood followed with the TS-990S. The Yaesu and Kenwood transceivers also include a preselector.
Many of the experts in receiver design prefer the dual-conversion (2 stages only) receiver architecture, with the 1st IF at 9 MHz +/-, because it offers a balance between receiving weak signals and blocking unwanted signals.
The higher quality receivers today are designed in such a way that the jitter is reduced to a minimum. Many modern transceivers feature a low internal noise floor, thanks to improvements in the components used to create the oscillator circuit and the receiver mixing and amplification components.
Back to the main topic:
So, while the internal noise floor has been greatly reduced, there is still the atmospheric noise to contend with, which we can do nothing about. I covered the source of atmospheric noise in a video a couple of years ago. Lightning from around the world combines to create a large portion of what we call atmospheric noise. And then there is man-made noise. This we can control to some extent. In this video I point out some of the primary sources of noise on the HF bands and how to investigate the noise source. Note that other sources of noise I didn’t mention in the video are can be garden lamps or the lamps in a greenhouse.
I hope you enjoy this video and find it helpful. If you find my channel informative and entertaining, I hope you will consider joining my support group by clicking on: www.patreon.com/N4HNH There are 3 levels of support, including exclusive content. Patreon team members gain insight from our technical discussions and internal polls. They also have the opportunity to view certain videos before they are released for public viewing.
N4HNH Radio has a Web site, where you can purchase T-shirts with some of the sayings you might hear in the videos. Some of the more prominent videos are featured there as well as a page geared toward ham radio training. Go to: www.n4hnhradio.com
Another great way to help support this channel is to click subscribe.
73, de N4HNH

[@donz7992]

Agree 100%. Had a terrible 80M and 40M noise floor when I began as a ham a couple years ago. Grounded things, ferrites, etc. didn't help. Like you suggest, I shut off all power in the house and ran off battery. Still there. Took off the antenna connection. Gone. So once I knew it was radiated emissions outside of my home, I walked the neighborhood with an AM radio. Noise increased near two poles. Much worse in rain / damp weather and wind. Sure enough, Xcel Energy found bad hardware on one of the poles I had identified and another about 1/4 mile away. They were great and I even have the tech's cell number should it come back. Now if I can just get rid of the spikes every 18kHz on 15M that come from my outside AC unit...

[@n4hnhradio]

You are fortunate to have such a responsive power company.

[@donz7992]

@@n4hnhradio Yes; they took it seriously but it did take 2-3 months to track, verify, report, schedule and correct it. But at least I did not have to convince them to do so.

[@allenpamscofield]

@@donz7992 Had similar with a street light buzzing causing interference. Called the utility company and it was fixed before the day was out. Just had to replace the light.

[@n4hnhradio]

You guys are so fortunate. My power company told me that they are “phasing out the RFI department.”

[@donz7992]

@@n4hnhradio Wow. That is unfortunate. From my conversations with utility co guys, these things are a lot more prevalent than we might think. I think Xcel Energy doesn't want to mess with another federal agency.

[@kaydenchristensen5011]

Next time I’m alone and at bunk house, I’m hitting the breakers and checking my noise floor. I don’t use 80m but my 40m noise floor can be pretty bad. Thanks for the video Doug!

[@n4hnhradio]

Hopefully it will be quiet, but quite often our noise floor includes objects within our own home.

[@wb4huc10]

Doug, I have noise sometimes that sounds exactly like yours. I too belive that it is power line noise. One thing that reinforces this belief is that my Yagi sits about a hundred feet from the suspect utility pole. When I aim the antenna at the pole the noise gets very loud, when I turn the Yagi sideways to the pole the front-to-side rejection of the antenna is good enough that the noise goes way down. I need to call the utility company and tell them about it but I haven't done that yet. And, like you, when it rains or is otherwise wet outside the noise goes away. Good luck, Mike - WB4HUC Austin, TX

[@n4hnhradio]

Mike, that definitely has the characteristics of RFI from a power pole. Usually loose hardware, dirty insulators, or blown lightning arrestor. Almost never the transformer itself, though the transformer is often blamed.

[@kenluning909]

Nice video. I too have seen an increase in noise in our area since 2012. It seems to vary in timing and strength in my area. Lots of new electronics that we all know really are not that "clean".

[@n4hnhradio]

The FCC seems to be less interested/able to keep up with the amount of new electronics hitting the streets these days.

[@n4hnhradio]

I just read an article that cites a study by the Radio Society of Great Britain. They have measured a 12dB increase in man-made noise in the VHF and UHF spectrum between a previous measurement (article doesn’t say when) and the latest measurement. Here is a link: www.arrl.org/news/noisy-electronics-have-increased-hf-vhf-noise-floors-in-uk-rsgb-reports-say

[@almartin806]

I have exactly the same type of noise on my FTdx 5000 and it turns out that the noise is caused by a LED street luminary about 300 ft from my antenna.

[@n4hnhradio]

LED lights are notorious for noise. It isn’t the LED itself but the power controller.

[@jameyevans29]

New ham here. My noise just started but this is my first winter on the band so do you think it could be from the dry air? My noise sounds identical to yours.

[@n4hnhradio]

Welcome to amateur radio! Dry air can definitely contribute to power line noise. It might only happen during the warmest part of the day but gradually get worse over time, until it happens constantly. Mine does that. There are around 60 playlists on my KZbin channel. There is one dedicated to HF Band Noise/RFI. There is also a collection on my Patreon site dedicated to noise and RFI. 73, de N4HNH

[@jameyevans29]

@@n4hnhradio Thanks for the reply! I’ll check it out 73 KQ4GDB

[@n4hnhradio]

Try the circuit breaker test to be sure the noise isn’t from within your own home. There are many noise sources in homes these days. But, if the noise is happening only during low humidity, it could likely be from loose or defective hardware on a power pole.

[@jeff7161]

Canadian smoke?

[@markwarren7116]

I have a S7 to S9 on 40 meters every day.

[@n4hnhradio]

Mine is that bad with the power pole noise. But it’s S9+10 or more on 15 through 6 meters. Still awaiting the power company to come fix their poles. It’s been a month since their engineer verified the problem.

[@JxH]

"Hot dry air" causes power line noise ("due to static build up"), as opposed to damp weather? Huh? I think you'll find that moisture contributes to leakage currents across contaminated (dirty) power line insulators, leading ultimately to tiny arcs that are the source of power line noise. A good rain storm can help to clean the insulators, so it can get a bit complicated trying to correlate things based on your own experiences. Power lines do not build-up static charges, since they're connected to the grid. The AC voltage goes up and down at 60 Hz with extremely low source impedance, so you'll never see a "static build-up" associated with power lines.

[@n4hnhradio]

I’m afraid you’re mistaken. You might want to have a conversation with the RFI engineer at your power company. I have. I’ve watched the entire process of finding the arcs, using infrared sensors and cameras. It’s a sophisticated system, housed in a Sprinter van with a hydraulic tower that pivots the sensor array in any direction. I’ve sat in the van and watched the process. The lower humidity (dry air) necessitates a higher potential of static charge buildup before there is a discharge. Moist air allows the discharge current to flow at a much lower voltage, lessening the amplitude of the noise. However, it is possible to have a high enough potential buildup that notable RFI can be generated in moist air. In my case, the potential of the lines is 14,400 vAC. As I type this, the hardware on two poles in my vicinity is so loose that I’m receiving RFI during high humidity. The engineer has already identified the poles and the specific hardware on the poles that needs to be tightened and cleaned. Now I’m waiting for a crew to come out and perform the work. But the frequent storms we are experiencing in the Southeast lately have my RFI low on the power company’s priority list. Here is an article from the ARRL: www.arrl.org/files/file/RFI/A%20Smarter%20Approach%20to%20Resolving%20Power%20Line%20Noise.pdf

[@JxH]

"One source of noise is due to the the heat generated by receiver components. This cannot be avoided." Not precisely. The first stage of receiver RF preamplification on an HF receiver is typically very low power, so the first transistor would be approximately room temperature. But even if you removed the cover and took it outside in winter and had a fan blowing cold air across it, you won't see any difference. The part of the sentence that I disagree with is "due to the heat generated", when in fact it is close enough to room temperature as to make no difference.

[@n4hnhradio]

I recommend that you search the Internet and read about Johnson-Nyquist noise. Perhaps the article at the link below will shed some light. Look specifically at page 47, the third column. “Noise is generated by the random motion of atomic particles inside circuit elements.” Continue reading and note that the temperature of the device generating the noise will determine the amount of noise. As atomic particles move inside the receiver components, thermal changes take place, creating noise. Add to this, phase noise, and you have the noise in your receiver before you ever connect an antenna. The signals from your antenna must be strong enough to overcome atmospheric (galactic) noise, man-made noise, and the thermal noise generated by the receiver itself. www.arrl.org/files/file/Technology/tis/info/pdf/020708qex046.pdf

[@robertkeller9828]

Call my electric coop and tell them they are emitting "noise", they'll send someone out to demand why you're wasting THEIR time and threaten to charge you with it "as a hobbyist". Problem is, SW is "WIMPY WEAK" signal requiring ridiculously HUGE antennas to even reliably receive. Radio makers put all the flashy lites and buttons without REALLY improving their equipments receivers and built-in filters. The FAA already considers the hobby a nuisance to commercial airplane communications!

[@n4hnhradio]

The FAA enjoys reliable communications that was pioneered by this “hobby.” A few years ago, my power company found two blown lightning arrestors causing my PLN. They thanked me. They have no way of knowing they’re blown until other equipment that they protect fails, which is costly. Furthermore, they are required by law to remedy RFI. My power company is trying to avoid having to correct the RFI of late, but Jeff, W4DD, did half their job for them, by pinpointing the exact source of the noise. I published a video about it. I wrote the FCC. The FCC turned it over to the ARRL. They ARRL sent Jeff. If the power company didn’t proved to be cooperative, the ARRL would get their legal team involved.