{"id":64348,"date":"2025-10-24T07:10:20","date_gmt":"2025-10-24T11:10:20","guid":{"rendered":"https:\/\/swling.com\/blog\/?p=64348"},"modified":"2025-10-24T07:10:20","modified_gmt":"2025-10-24T11:10:20","slug":"taming-the-noise-don-moores-simple-cheap-filter-solution-for-traveling-dxers","status":"publish","type":"post","link":"https:\/\/swling.com\/blog\/2025\/10\/taming-the-noise-don-moores-simple-cheap-filter-solution-for-traveling-dxers\/","title":{"rendered":"Taming the Noise: Don Moore\u2019s Simple, Cheap Filter Solution for Traveling DXers"},"content":{"rendered":"

Many thanks to SWLing Post contributor\u00a0Don Moore<\/a>\u2013noted\u00a0author<\/a>, traveler, and DXer\u2013who shares the following post:<\/em><\/strong><\/b><\/p>\n

\n

A Cheap and Simple Noise Filter<\/b><\/h1>\n

By Don Moore<\/b><\/h4>\n

Don\u2019s traveling DX stories can be found in his book Tales of a Vagabond DXer<\/a> <\/i>[SWLing Post affiliate link]<\/i>.<\/i><\/b> If you\u2019ve already read his book and enjoyed it, do Don a favor and leave a review on Amazon.<\/i><\/p>\n

My DXing career started over fifty years ago in an upstairs bedroom in tiny Milesburg, Pennsylvania. I had a consumer-grade multi-band radio and some copper wire strung from the roof to a nearby tree.\u00a0 It was a simple setup but it worked very well. Do you know what I didn\u2019t have? A noise problem. The only time I remember noise ruining my DX was when my mother was using the electric mixer and that meant she was making cookies or a cake. I never complained.<\/p>\n

Times have changed, haven\u2019t they? What DXer doesn\u2019t complain about noise these days? I know people who have left the hobby because the place they lived at and DXed at for decades gradually became so noisy they couldn\u2019t DX anymore.<\/p>\n

Unsurprisingly, a lot has been written about how to find and eliminate noise in your home. However, most of my DXing is done as I wander the globe. I try to find places to stay at that should be good for DXing. But no matter how good a place looks beforehand, there\u2019s no way of knowing what the noise level will be until I get there.<\/p>\n

As a traveling DXer, I need quick, easy, and compact noise solutions. The best solution I’ve found are these CCTV distortion filters (ground loop isolators) that Brett Saylor recommended to me several years ago.<\/p>\n

\"\"<\/a><\/p>\n

\"\"<\/a><\/p>\n

No, these weren\u2019t designed for radio use. And they aren\u2019t a miracle solution that will eliminate all the noise that plagues DXers. Sometimes they\u2019re no use at all. But I\u2019ve DXed in dozens of locations over the past ten years and there have been multiple occasions where one of these filters has turned what would have been a disappointing stay into a good DX session. I don\u2019t go anywhere without two of these packed in my mobile DX shack.<\/p>\n

But let me show you some results. All of these SDR screenshots were made with SDR-Console using an Airspy HF+ Discovery SDR connected to a PA0RDT mini-whip antenna.<\/p>\n

I spent last summer in the north suburbs of Chicago and several times went to a park to test my DX equipment. Around midday, the lower shortwave frequencies were filled with noise peaks. On this first image, it\u2019s hard to pick out WWV on 5 MHz from all the noise peaks. In the second image the filter hasn\u2019t totally eliminated the noise, but WWV\u2019s signal is now strong and clear.<\/p>\n

\"\"<\/a><\/p>\n

\"\"<\/a><\/p>\n

The noise was nearly as strong on 49 meters but the filter almost totally eliminated it. CFRX\u2019s signal on 6070 kHz was slightly weaker with the filter, but it was significantly more listenable without the noise.<\/p>\n

\"\"<\/a><\/p>\n

\"\"<\/a><\/p>\n

Which frequencies noise affects can vary between locations. At that park the noise was gone above about 11 MHz.\u00a0 While traveling across the US in mid-October, I stopped at a park just west of Kansas City to do some more DXing and equipment tests.\u00a0 The noise there was bad in the middle shortwave bands, such as in the 25 meter band.<\/p>\n

\"\"<\/a><\/p>\n

But the filter did a good job cleaning it up.<\/p>\n

\"\"<\/a><\/p>\n

Finally, about two years ago when I was DXing in Rafina, Greece, the noise was bad on the higher bands. Here are before and after screen shots on the 16-meter band.<\/p>\n

\"\"<\/a><\/p>\n

\"\"<\/a><\/p>\n

These filters should work with any coax-fed antenna. I\u2019ve used them with beverages, Wellbrook loops, the PA0RDT, and the MLA-30+ loop. If the antenna has an interface, such as the last three mentioned, the filter goes between the interface and your receiver (and not between the interface and the antenna).\u00a0 I\u2019m not sure what the impedance on these is, but I\u2019ve used them with both 50- and 75-ohm coax cable.<\/p>\n

Sources of the Filters<\/b><\/h2>\n

An Internet search for \u201cCCTV Ground Loop Isolator\u201d brings up all kinds of products. They are probably all the same but I have no way of knowing that. So I recommend getting the exact ones that I have purchased. Just compare the product to the pictures of mine.<\/p>\n

Here are links to three current sources for these exact ones on Amazon. They can also be found on eBay and other sites. [Note that all of these links are affilliate links that support the SWLing Post at no cost to you.]<\/em><\/p>\n