Tag Archives: QRM

Guest Post: More Anti-Noise Ideas

In a previous guest post, SWLing Post contributor TomL, shared his “Evolving, Morphing, SW Listening Station” where 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 RFI environment)

by TomL


I have made the following changes:

  • Created a prototype mini-loop based on a crossed-parallel idea from VE1ZAC (Jeff).
  • Added a balun from LNR Precision (Parfitt’s EF-SWL) in an experimental configuration.
  • Added to the balun, an outdoor amplifier – Wellbrook ALA-100M.
  • Added a noise canceling unit (MFJ-1026).
  • Added 2 preselectors, an old Grove TUN-3 connected to the main loop feed and an MFJ-1046 connected to the ground connection of the balun. Both feeds go into the MFJ-1026.
  • Added BHI Compact In-Line DSP filter and two switch boxes to cut it in/out as needed.
  • Added a medium wave noise canceling unit that I have not figured out how to use yet. (Quantum Phaser). The MFJ unit does not work on medium wave without modification.
  • Purchased from eBay a used Grundig Satellit 800, a somewhat more robust fixed-station receiver to replace my aging Sony ICF-2010.
  • Other non-related (not shown): Whistler digital scanner + UHF over-the-air TV + FM broadcasts + an AM/FM HD digital radio + high pass filters from MiniCircuits.com – (audio from all these sources is passed to an existing high fidelity stereo power amp and NHT Super One speakers on the computer desk for near-field monitoring). Associated antennas are also hidden on the outside deck (shhhhh!).
  • Large charge card balance!!

So, here are some pics for the crossed-parallel loop. VE1ZAC web site has all the references if you want to explore further or google him. Mine is purely a prototype and not finished. And should eventually be placed on a rotor (but how to keep my Nazi-like condo association from finding out?!?!?!?).


It is three 14 inch quilters hoops from Joann Stores plus some 1-inch copper strips cut from a small 2 meter roll of thin copper from eBay. Then, it is wired in parallel with silver-plated aviation wire on each side with a feed in the middle. Not an optimal placement of the feed, (should go straight down along the pipe). Will fix things up whenever I get some more time.


Seems to be an efficient way to prototype small loops. It is now mounted on a short ¾” inside diameter PVC pipe into a cheap plastic sand-filled deck-umbrella stand. Loops are light and somewhat flimsy, so I mounted the three loops on a plastic triangle ruler and dowel sticks glued to the sides for some extra strength. Good enough for now.

The EF-SWL balun is also in an experimental configuration. Since I read somewhere that loop antennas have a very low impedance at the feed point (like, 10 ohms or lower), I thought I might try a balun that is meant to lower the impedance and mount it backwards. I don’t have a picture of it but the SO-239 output is facing the loop and the screw terminals are facing the direction of the radio. My feeble brain thinks since it is a passive device of coils on ferrite, it should work bidirectionally for receive only applications like this. It seems to work but I have the excuse that I really don’t know what I am doing! 🙂


BHI unit in action.

The BHI DSP filter is useful in some circumstances but I find it fatiguing to listen to. The audio from the Sattelit 800 is so nice, I mostly like it without the DSP. The DSP narrows the bandwidth significantly, somewhere around 4 kHz or less from my hearing. I like that the Grundig has two tone controls. And it also has a stable SSB and on very strong signals with clear audio, I like to listen with SSB lower or upper sideband. But the DSP is useful at times for hash-like noisy signals; it is not quite as good on buzzing noise and I wish the Satellit 800 had a noise blanker, but that would have been a more costly purchase, like a Drake R8A.

So, in a nutshell, I have a discovery about noise here: it is all around me and ubiquitous, like the air I breathe!

I find it hard to null and also worry about peaking a station signal at the same time. However, I do have a lower noise floor with the experimental loop sitting outdoors, especially on medium wave (the Wellbrook amp + loop works great on the lower frequencies – am able to get eight different medium wave stations carrying Major League Baseball games at night – it would be nine to get WFAN for the New York Mets but the local Chicago Cubs station covers the adjacent frequency with horrible digital hash! ***Bleeping*** digital junk!).

Also, the signal level is noticeably lower using the loop. Then, add in the effect of the MFJ Noise Canceling unit, the usable signal gets even weaker.

The bottom line is, I can now finally enjoy listening to many SW broadcasts, BUT only the strongest signals. Anything else is still hopelessly lost in the noise. So, gains are limited.

On the other hand, and something else I learned by doing is that, any 1 or 2 dB signal/noise ratio improvement will help with the final audio output in the end product. Using low-noise amps, loops, noise canceler, preselectors, grounded connections, ground isolators at the input of every receiver, high quality stereo amplifier and speakers, tone controls, SSB vs. AM Sync, weird antenna configurations, etc, etc. It all helps in the end to some degree.

Tinkering is an art that involves a lot of thinking/doing iterations! And high quality parts must be used all along the chain or it could degrade the signal.

Below are some audio samples, not very well recorded, but can give some idea of the incremental improvement with each enhancement (turn up the volume). NOTE: other people may get better or worse results depending upon individual situations, type of antennas used, etc, etc.

Recording 1: R. Marti. First 10 seconds an indoor antenna with no noise reduction, second 10 seconds the outdoor loop without the MFJ-1026, the third 10 seconds with the MFJ-1026, then switched off and on to hear the difference.

Recording 2: R. Marti. MFJ -1026 is ON. Last 15 seconds is SSB, very thin sounding. Really only good for strongest signals. I liked the AM Sync better (Satellit 800 is really a Drake SW8 in disguise with a quality AM Sync). But, SSB can sound excellent with very clear voices with a steady and strong signal (The Satellit 800 does NOT have IF-shift or a BFO to fine tune an SSB reception, so the station must be exactly transmitting on the kHz mark, which most are nowadays).

Recording 3: R. Marti. MFJ-1026 is ON. Last 20 seconds you hear me switch in the two audio switches and the BHI DSP is on its lowest setting. Narrower and clearer with some reduction of background noise. I find I only like going up to about 4 on the DSP dial, after that the audio fidelity starts getting more choppy with digital artifacts that sound like dripping water. I tend to like higher fidelity. One nice thing about the BHI DSP is a faux-stereo that helps a little with voice intelligibility by helping the brain naturally filter the noise. Faux-stereo is ON even when the noise reduction circuit is manually turned off (power must be on and bandwidth still sounds narrowed).

Recording 4: R. Nacional Brazilia. First without MFJ-1026, then ON, then OFF, then ON, then with the BHI kicked for the last 20 seconds.

Recording 5: Greece. Switching the MFJ-1026 on and off every 5 seconds. In this particular case, the signal was weak and fading a lot. The MFJ OFF was also weaker than with it turned ON. That is interesting behavior, usually it is opposite. It pays to play with the settings a little. At other times, and less frequently, the MFJ unit turned OFF sometimes sounds better than with it ON and tuned for less noise. Go figure!

After all the tweaking is done, and I cannot get any more performance out of this, I will probably have to move to a nice, quiet neighborhood and setup a nice antenna farm!!

In the meantime, I do enjoy listening to the stronger stations from North America, Cuba, Brazil, Europe, and Australia with less noise than before.


TomL from NOIZEY Illinoiz

Once again, Tom, thanks for sharing your RFI elimination journey!

I love how you take on this noisy problem by experimenting and seeing it more as a challenge than an obstacle to enjoying your hobby.  Great job! 

AirGig: a new BPL technology that promises less RFI


Many thanks to SWLing Post contributor, DanH, who writes:

I read this news item today. AT&T has a new approach to broadband over power lines called AirGig. Supposedly, this technology will avoid RFI issues encountered with previous BPL technologies. This shouldn’t be an issue in my neighborhood where power lines are underground. Underground utilities still have RFI issues. My next door neighbor’s AT&T high speed internet swamps out all nearly all shortwave signals below 4.7 MHz within radius of 30 feet from the connection box.


Many thanks, DanH! Here is a short promo video for AirGig:

Phil demonstrates the BHI NEIM1031 Noise Eliminating In-Line Module


Many thanks to SWLing Post contributor, Phil Brennan, who writes:

[Recently] one of your contributors mentioned that he purchased a BHI DSP unit at a discounted price. I purchased one (a different model to the one in the previous post) some months ago before I headed away travelling.

The post reminded me that I had made a small video demonstrating the DSP unit on my FRG7. The video shows me tuning the DSP on a broadcast of Voice of the People on 3912 khz. While QRM at my place isn’t too bad, it’s still present and the DSP does aid in clearing up a signal.

Voice of the People is usually jammed by the DPRK and the DSP also assists in reducing the roar of the jammer. Of course one can go to far with DSP and the audio can suffer from that underwater sound.

Thank you, Phil! The FRG-7 is an ideal receiver for something like the BHI module since it precedes on-board DSP. The great thing about an in-line module, of course, is that it can be used with a variety of receivers.

Click here to view the BHI NEIM1031 MKII on BHI’s website.

Selecting a budget antenna for urban radio listening


Yesterday, an SWLing Post reader contacted me with questions regarding budget antenna choices for an urban apartment. He’s about to purchase an SDR, but knows that a decent antenna capable of coping with urban radio interference is a critical component.

I suggested that, since I’m no expert with urban interference, he pose his question to the SWLing Post community. Here’s his reply and request:

I know I’m a little behind some of my other radio friends, but I’m finally moving up to a software defined radio. Specifically the affordability of the SDRplay RSP and all good reviews for it have encouraged me to make the leap.

The SDRplay RSP software defined radio

The SDRplay RSP software defined radio

I suppose it should go without saying that once I purchase an SDRplay I would like to use it, which might not be so easy. I live in a big city full of RF pollution, and most of my listening will be in a room where there’s a fair amount of electronic gadgetry.

So, without spending a lot of money, I’m curious if any of your readers might have suggestions about what I might purchase as a “starter kit” for a new SDR user in such a scenario. I also plan to take the SDRplay with me when I have forays out of the city, but I envision that some sort of long wire might be sufficient for listening out in the countryside.

I live on the second floor in an urban apartment, and have two windows in the room where I’ll be listening. There is zero chance that I can hang or attach anything on the outside of the house here. So, my most pressing question is about antenna ideas. I’ll need something inexpensive, as I mentioned, and something “off the shelf.” I don’t have the skills or tools to really “build” anything, unfortunately. So is there some less than pricy antenna or antennas I should look at? Or is there some hope of doing something with a long wire indoors?

Tecsun AN-100 portable loop antenna

Tecsun AN-100 portable loop antenna

And will my little Tecsun AN-100 AM loop antenna going to help me at all? I mostly plan to listen to MW and the HF bands, but I will inevitably check out signals far up the bands as well. So advise about listening to these bands is also of interest to me.

Other than that, I understand it’s important to attach the SDR to the laptop with a USB cable with ferrite chokes. And it probably wouldn’t hurt to buy some extra ferrite chokes to attach to other cables I might be using. I also plan to buy a NooElec mini-balun for use with a long wire antenna, and I already purchased a PowerMate USB knob because I still prefer to do my “tuning” that way.

So other than those basics my questions would be regarding connecting cables and adapters, and the best lengths of cable to use. Should I have some cable between the balun and SDR? I believe I’ve read that it’s better to have a longer USB cable and a shorter coax to the antenna, correct? And when it comes to using a wire antenna, are there preferences as far as what type or gauge of wire to use?

I am also interested in any general suggestions or tips from SDR users on getting started. In general, I’m pretty good with navigating through software, it’s usually the hardware issues that stump me. I’m looking to spend between $100 to $150 tops on everything besides the SDR, and I’d like to hear about peripherals, cables, adapters and connectors which when added all together won’t bust my bank.

I’m sure there’s plenty of people who read this wonderful blog who have plenty of useful knowledge regarding SDR listening on a budget. And I hope a few could share a little of their experience and collected wisdom on this topic here, for me and for others considering turning their computers into receivers…

Indeed. I appreciate this reader’s question, since many listeners live in environments with heavy radio interference. While we’ve published a number of posts touting the virtues of magnetic loop antennas, I don’t think we’ve ever looked for solutions at or below $150 US. While this may be a challenge, I’m also certain there are a number of readers who’ve found solutions to this problem.

So, Post readers, what might you do–or have you done–in similar circs?  Please feel free to comment, and let’s explore inventive and affordable solutions for this reader!

RFI from solar power installations


(Source: Southgate ARC)

The Netherlands national amateur radio society VERON reports on the pollution problems caused by Solar Panels installed on homes

Electrical systems such as solar panel installations must comply with EMC (Electro Magnetic Compatibility) standards. That means that there is a limit to the electromagnetic fields (EMF) that an electrical system, such as the combination solar panel and inverter including cabling, may emit.

However, a 2014 study in 14 European countries by the EMC Administrative Cooperation Working Group found this emission limit is more often than not exceeded.

Read the full story in Google English at