Category Archives: QRM

Post-storm power outage leads Emilio to find the RFI-spewing source of his problems

Storm with lighteningMany 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 my feelings were so dampened with this terrific RFI–only the lower Broadcast Band (900 to 540 Khz) was relatively immune to it.

Yesterday, we had a storm and the mains electricity service went off, so I connect a 12 volt battery to my RT-749b military surplus transceiver and the received signals were very clean like the “good old days”.

(Above: Listen W1AW loong distant from my QTH in Chiapas Mexico).

When the power electricity come back on, so did the RFI too!!

(Above: W1AW gone)

Remembering the recently publish post in SWLing Post about RFI, I did some testing by
cutting the electricity to my home (the main switch) and the RFI was gone!! So I discovered the RFI lives in my house–not in the outside wires!!

I put batteries in my old shortwave portable radio and searched (like Ghostbusters) all outlets contacts, one by one, connect and disconnected each device.

And I found the guilty party!

Exhibit A: The Mitzu laptop power supply

On December 2019, the power supply of my son’s laptop broke, so I bought a cheap substitute.

The RFI produced by this little monster could be heard at a distance of about 200 meters from my QTH!!! (Much like an old transmitter spark gap–!)

Even this cheap power supply apparently featured ferrite toroids on the wire but turns out it is fake!! It was only a plastic ball!

Exhibit B: Fake toroids!

The wires were also not shielded. No doubt one of the worst switched-mode power supplies I could have purchased.

Exhibit C: The Mitzu RFI generator wire without shield, only pair wires!

I found a old Acer power supply with same specs and I replaced out the RFI monster one.

And now? The shortwave bands are clean again.

(Video: Testing my Kenwood R-600 rx with Radio Exterior de España… plugging and unplug the Mitzu monster RFI generator).

So I wanted to share what happened to me, so perhaps it can be useful for other SWLing Post blog friends.

Watch these little switched mode power supplies from all devices in your home. Replace them if you detect RFI levels that harms SWLing. Consider disconnect all devices (vampire consumption–or phantom loads) if not in use; the radio waves and electric bill will be grateful to you!


WOW! What a difference! Emilio, that was great investigative work on your part. It’s as if that switching power supply was specifically designed to create RFI! No shield and fake toroids? That’s just criminal in my world! 

Thank you so much for sharing your story. Hopefully, this might encourage others to investigate and apprehend their own local RFI monsters!

(And by the way, Emilio, I love that RT-749b military transceiver!)

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QRM-busting: Rob’s practical approach to tackling unwanted radio noise

Our good friend Rob Wagner (VK3BVW) over at the  Mount Evelyn DX Report has posted an excellent article on how to deal with man-made radio interference (QRM/RFI) in our homes and neighborhoods. This has been a frequent topic here on the SWLing Post (indeed, as recently as Thursday).

I’ve copied an excerpt from his article below, but I highly recommend reading his entire post which includes practical ways you can investigate and mitigate RFI within your home and neighborhood:

Mount Evelyn is a semi-urban, semi-rural location, about 45 kilometres east of Melbourne, the southeastern part of Australia. When we retired eight years ago to this lovely mountain region known as the Yarra Ranges, noise levels on the shortwave bands were quite manageable. At times, it might rise to perhaps an S3, but hanging a variety of antennas cut for a mix of bands and erected in different directions certainly allowed for some flexibility and control over the local man-made noise.

Previously, we lived in a highly urbanized environment where 24-hour S9 noise levels prohibited any SWL or Ham activity from home. But moving to more spacious living at Mount Evelyn allowed me to drag out the radios, string up those wire antennas and really enjoy again the hobby that was such a part of my youth.

But over the past 12 months, I have noticed an increase in local man-made noise around here. The level of general electrical hash on the bands has increased markedly. At certain times of the day, the S-meter is rising to between 5 and 7. And it is not always predictable when the noise levels will rise and fall.

A few weeks ago, the local electric company decided to do a major overhaul of some power poles and wires in an area not far from here. So, the entire region was without power for about seven hours. Fantastic, I thought! I’ll hook up the Yaesu FTDX3000 to the 12v sealed lead acid battery and do some daytime DXing right here in the shack in a totally noise-free environment. Once the lights went off, I fired up the rig and tuned the bands in search of weak signal DX delights.

Err….well, not to be! Indeed, the results were somewhat underwhelming! It was disappointing just how much man-made interference was evident on the shortwave bands, even though such a large area around Mount Evelyn was without power. The hash was still registering a steady 3 on the S-meter. Certainly, it was better than when the mains power is in regular operation. But in the past, when the power had been off, the noise dropped right away, and battery-powered DXing from the radio shack was a real pleasure. But alas, not on this occasion!

So, I began thinking about why this was so. What is going on here?[…]

Click here to read the full article at The Mount Evelyn DX Report. 

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Can’t receive anything on your new shortwave radio–? Read this.

This morning, I received a question from Andrew, an SWLing Post reader in the UK.  Andrew writes:

May I ask a question please? I am very much a newbie to this. I am not really interested in FM, but I would like to listen to international stations on SW, utilities stations, amateur broadcasts and if possible, local airports, aircraft on air band.

I have just purchased a Tecsun PL-680 and have tried it inside my home with the telescopic and wire aerial that came with it, plugged into the antenna port and clipped to a point near the ceiling. All inside the house and the wire aerial did improve the reception, but I get hardly and channels either during the day or night.

Grateful for your detailed advice on what I need to do exactly to improve the number of stations I can receive.

Kind regards
Andrew

Thank you for your question, Andrew, and I hope you don’t mind that I share it here on the SWLing Post as I receive this question so frequently from new shortwave radio enthusiasts.

Of course, a number of things could be affecting your shortwave radio reception and there is, of course, the possibility the receiver is faulty–however, this is very unlikely. Let’s talk about what is most likely the culprit:

Radio Frequency Interference (RFI)

RFI is quite often the elephant in the listening room. It’s not always immediately obvious–especially if you’re new to shortwave listening.

RFI (also known as QRM) is radio noise that is created locally and often concentrated in our homes and neighborhoods. RFI deafens our shortwave radios by overwhelming the receiver with strong spurious signals. Even if you can’t hear the noise, it could still be overwhelming your receiver from a different portion of the band.

RFI can emanate from most any modern electronic or digital device in your home: televisions, power supplies, dimmer switches, smart appliances, and even computer hard drives. Honestly, most any device could be the culprit.

These “Wall Wart” type adapters can create a lot of RFI

RFI can also be caused by power line noises outdoors which have a much larger noise footprint and typically require intervention from your local utilities company/municipality.

In all likelihood, though, it’s a noise inside your home.

There’s a quick way to determine if RFI is the culprit:

Take your radio outdoors, away from the noise

Depending on where you live, this might only require walking with your radio to the far end of your garden/yard, or it might require hopping in your car and visiting a local park. The idea is to find a spot far removed from houses and buildings, outdoor lighting, and even power lines if possible.

Once you find a listening spot, turn on your portable and tune through some of the popular shortwave radio bands.

If in the late afternoon or evening, I like tuning through either the 31 meter band (9,400–9,900 kHz), 41 meter band (7,200–7,450 kHz) and, if late evening, the 49 meter band (5,900–6,200 kHz). Jot down the frequencies where you hear stations and perhaps even make notes about the signal strength. Then go back home and see if you can receive as many stations. Shortwave stations change frequencies often, but if you listen from home at the same time the following evening, the radio landscape should be similar.

My guess is that you’ll hear many more stations in the field than you can from within your home.

Living with RFI

Sadly, RFI is just a fact of life in this century. It’s very hard to escape, especially for those of us living in dense urban areas. This is one of the reasons I’m such a big fan of taking radios to the field.

There are things you can do to improve reception and I would encourage you to read through this post from our archives (the first two points in the article directly address RFI). Do your best to track down sources of noise and eliminate them.

If you find that, even in the field, your shortwave receiver can’t receive stations with the antenna fully extended, then it may indeed be an issue with the radio itself and you might need to send it back to the manufacturer or retailer if it’s within the return window.

Post readers: If you have other suggestions, feel free to comment!


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John works with FCC to track down WX radar interference

Photo source: John (AE5X)

Many thanks to SWLing Post contributor, John Harper (AE5X), who notes that he recently worked with an FCC crew to find the source of noise that was affecting a weather radar site. In the process, John got to check out, first hand, RF Hawk and some of the equipment the FCC uses to locate interference (including pirate radio stations).

Click here to read John’s full post.

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Contayner Over-The-Horizon Radar site polluting the HF spectrum

OTH radar Contayner on 7062 and 7103 kHz on 21 Oct. at 1847 UTC (Source: IARU Region 1 Newsletter)

Many thanks to SWLing Post contributor, Paul Evans, who writes:

The news from IARU Region 1 observer reports is all over the radio internet (including news sites and other blogs), but the extent of this [Russian] OTHR is grim. [Click here to read a recent ARRL News post.]

It is also entering service on a full-time basis, along with, potentially, a similar Chinese system.

Yes, it has been in testing for many years but is approaching multiple site use, soon. As the sunspot cycle comes back they may prove to be very limiting.

The antenna picture (for the transmit site) is impressive:
https://qrznow.com/russian-oth-radar-now-reported-to-be-everywhere/

(although I think that is of the old Woodpecker site, the Google Maps street view image looks somewhat different, see below).

However, it’s not so huge that it really stands out. It can be seen here:

in satellite view and can even be seen in street view here:

Note that the magic number in the phased arrays seems to be 9.

Rather worrying is that the UK continues to run, over many years now, OTHR from sovereign bases (ZC4) in Cyprus rather obviously aimed at use in Syria and Libya for use with the RAF and for Russian air space. It too can be seen on the salt marshes in the south of the island. As an active system it seems to be rather more cloaked than the Russian system, although there are some 360 degree images in Google Maps that show the towers. This was extremely annoying on the bands when the last solar cycle was near maximum from Bermuda because it was right in the main lobe when a Yagi was pointed towards Europe and was very loud. It was considerably narrower than the Russian system but occupied a solid chunk of band.

Paul, thank you for bringing this to our attention. I have seen chatter about the QRM this particular Russian OTH Radar site has created, but it seems other countries will soon be joining the OTHR QRM scene as well.


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Hamvention Highlights: Affordable diversity reception with the SDRplay RSPduo

Each year at the Dayton Hamvention I enjoy checking out the latest radio products and services. This year (2019) I found an exceptional number of innovations and will share these in Hamvention Highlights posts. If you would like to check out 2019 Hamvention Highlights as I publish them, bookmark this tag: 2019 Hamvention Highlights

Diversity reception with the SDRplay RSPduo

Last year, during the 2018 Hamvention, SDRplay announced the RSPduo, a 14bit dual-tuner SDR. We posted a review of the RSPduo on the SWLing Post.

At the time, SDRplay mentioned that the RSPduo could eventually be used for diversity reception.

Diversity reception is the ability to combine or select two signals, from two (or more) antenna sources, that have been modulated with identical information-bearing signals, but which may vary in their fading/noise characteristics at any given instant.

In short, diversity reception gives one a powerful tool to mitigate fading and noise, and to improve a signal’s overall integrity.

Andy and Mike with SDRplay demonstrated SDRuno’s diversity reception functionality and noted that it will soon roll out as a free upgrade to SDRuno, SDRplay’s open SDR application.

I should note here that the SDRplay booth at the 2019 Hamvention was incredibly busy—no doubt, because the RSPduo must be one of the least expensive, most accessible, ways to experiment with diversity reception. Case in point: the new Elecraft K4D transceiver will support diversity reception, but the price is about $4,700 US; the RSPduo can be purchased for $280 US.

Based on the demonstration, this feature will be quite easy to use and I love how it has been implemented in the SDRuno GUI (graphical user interface).

To learn more about the RSPduo, check out SDRplay’s website or read our review. Of course, when SDRplay releases the diversity reception upgrade to SDRuno, we will make an announcement!

If you would like to follow other Hamvention Highlights, bookmark the tag: 2019 Hamvention Highlights

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Arcing can produce nasty broadband radio interference

On this trip to Québec, indoor listening has been more productive than listening from our balcony.

I mentioned in a previous post that, this year, QRM levels here at the condo in Québec are higher on our balcony than they are inside the building.

I think I found the source.

A couple weeks ago, on my morning walk, I passed underneath some high voltage power lines about 1 km from the condo. I noticed the sound of arcing coming from a pole nearby. No doubt, something metal–a staple, a cable, a pin, etc.–is the culprit.

I pulled out my smart phone and made this short video. If you turn up the volume, you might hear the noise especially at the end of the clip.:

I took a portable radio back to the site later and heard the same broadband noise I heard from the condo.

Although we only rent this condo a couple months a year, I’ll try to report the noise to the Hydro Québec. I know that our utility company in the States must follow up with requests like this and do their best to eliminate unintentional sources of RFI. These issues can also be an indication of something in the system failing, so power companies can actually be quite grateful for the feedback.

If you have persistent broadband noise at home, check out some of the trouble shooting tutorials at K3RFI’s website for a little guidance.

Despite all of this noise, I’m pleased I can still receive a few of my favorite shortwave stations. And, of course, escape to the KiwiSDR network and hit the field from time to time!

No worries, though, I’ll be back at my home station soon and can once again enjoy a relatively RFI-free radio space!

Post readers: Have you ever been plagued with power line noise? What did you do about it? Any tips? Please comment!

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