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

toml-radios

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?!?!?!?).

loops

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.

loops-closeup

loops-closeup2
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

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.

73’s

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! 

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7 thoughts on “Guest Post: More Anti-Noise Ideas

  1. Pingback: Dave’s review of the MFJ-1026/1025 and regulated AC adapter recommendations | The SWLing Post

  2. Joe patti

    I dunno. I had a MFJ 1026, but could never make even a dent in the noise level in my South Jersey location. Even using an outdoor antenna. The only time I can get anything close to a lower noise floor is when the power goes out and the neighborhood is dark….

    Reply
    1. TomL

      Joe,
      I still have high noise levels but the small loop + amplifier + preselector helps, too. It took me 6 months of trying different noise antennas with the MFJ and the noise reduction is modest on many stations but sometimes very large. I gave up twice during that time too. And the homemade loop could have better nulls and its reception pattern is not perfectly figure-8, but it works.

      I have found noise is least at early mornings (4am – 8am) and there are some signals from the North that come in a little better, like R. Taiwan, but still faint and buried in the noise. I am hoping to get some sort of rotator that has a low profile to help peak the signal while the loop is outside. Then, I want to see how the MFJ performs with a desired signal that is a little stronger. We’ll see (Bescor MP-101 looks promising although not waterproof).

      Noise sucks but I am trying my best to stay off of monthly media subscriptions. I get to save money and spend it on things more important to me. That’s just me, others may have other motives.
      Tom

      Reply
  3. George - NJ3H

    Thanks for your efforts and your findings. I have been dealing with a lot of interference since moving from Virginia to here in central Oregon last January. Most recently, I have been hearing motorboating from 6-13 mhz, continuous. Took a portable SW receiver and found the culprit house. Talked with the young couple living there. Turns out it was from some crazy internet system that uses the house wiring. He told me within a couple of days it will be replaced. Most kind and understanding of them. I even offered to help pay and they said absolutely not. WOW! My Perseus, Elad, and I are happy for the moment.

    Reply
    1. TomL

      George,
      You have wonderful neighbors. Fostering understanding between people is part of what radio is all about anyway.

      And I think I am becoming a fan of loop antennas. Of course they cannot do everything but can be very useful. I wish someone would invent a receive loop antenna that could be tuned remotely, cancel noise/unwanted signals automagically, rotate as needed, and also shape the audio as well – and all fit in a small outdoor space. All these different pieces can be awkward and expensive to experiment with!
      TomL

      Reply
  4. Kire

    Whats funny about noise is that we are mostly completely oblivious to it unless we delve into radio. I am lucky to live in the country in a trailer with no ac, just 12 volt. Even then, every little appliance (fans, tv, small amp) will add noise. Thankfully i’m not rf sensitive myself, or maybe I am torn up enough to no longer feel it. LOL.

    Reply
  5. Pingback: Guest Post: More Anti-Noise Ideas – dxradio.de

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