Tag Archives: Don Moore

A Mystery Station from Vietnam

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By Don Moore

Don’s traveling DX stories can be found in his book Tales of a Vagabond DXer [SWLing Post affiliate link]. If you’ve already read his book and enjoyed it, do Don a favor and leave a review on Amazon.

Since early November, I’ve been traveling and DXing in Southeast Asia. I’ll write more about that in a few future articles, but I came across something new that I can’t wait to share. It’s unusual and possibly might meet the criteria to be considered an SWBC (shortwave broadcast) station. If you’re in this part of the world, it shouldn’t be too hard to log. In other places, it will be a serious DX target to try for.

A few nights ago I was using the SDR-Console Data Analyzer tool to look for voice air and maritime communications in some spectrum recordings I had made on 11 December in Pakbeng, Laos. On 8101 kHz USB, I came across a strong signal with a very polished program that wasn’t anything at all like a utility broadcast. It started at 1217 UTC with a little music interlude, an announcement by a woman, a bit more music, then into some kind of documentary talk, all in an unknown language. My recording ended five minutes later, so I had no idea how long it went.

A few years ago it would have remained a total mystery but technology has given us some very helpful tools. To identify the language I began playing it into Google Translate on my phone. The second try identified the language as Thai. Here’s the English translation of the initial program announcement:

Greetings to the people and viewers. I invited the people and the audience to listen to the Duyen Hai information program broadcast from Duyen Hai Vietnam Information System. Today’s program on December 11, 2025, at 19:05 has the following content.

I heard this at 1217 UTC, which would be 1917 in Southeast Asia. So the broadcast was delayed by twelve minutes. After a brief bit of music there was a talk about the fishing industry in Hai Long Bay in Vietnam. And the language was Thai, not Vietnamese.

Here’s the audio of my reception in Pakbeng. Set Google Translate to translate from Thai to English and play it on your phone. It may take a couple of tries to get it to work.

This really sounded to me like a regular broadcast program. I started looking through the other spectrum recordings I had on hand for ones with the same time and frequency range. I found the same broadcast starting at 1214 UTC on 20 November (heard in Taal, Philippines) and at 1215 UTC on 03 December (heard in Trang An, Vietnam). The programs followed the same pattern and ended about fifteen minutes later. One program was an interview and the other another documentary. The signals were not as strong or clear so it was difficult getting Google Translate to work with them but I was able to ascertain that the language was still Thai and that the topics were fisheries and economic development.

I also have with me some spectrum recordings from an October DXpedition in Pennsylvania. I found the same program around 1215 UTC on 8101 kHz on those on 30 and 31 October. In Pennsylvania the signal was barely there but on peaks I could tell it was the same woman’s voice. So this appears to be some kind of regular program and it’s been going on for at least two months. But what is the Duyen Hai Information System and who is behind it?

There is a Duyen Hai Power Station in the far south of Vietnam. But the most likely explanation would be a connection to Vu Duyen Hai, the Deputy Director of Fisheries and Fisheries Resources for the Vietnamese government. There are numerous articles about him on the Internet. He’s been very involved in trying to make sure that Vietnam’s fisheries industry is ethically managed according to international standards.

So this appears to be some sort of regular broadcast in which the Vietnamese Fisheries department attempts to inform people in the Thai fishing industry as to what their Vietnamese counterparts are doing. To do that it would make sense to use an existing marine transmitter in the marine band since Thai fishing boats would have radios to receive this. But we don’t know if this being done officially by Duyen Hai Information Systems or if someone else is unofficially relaying the station on the marine band.

But you don’t have to be a Thai fisherman to tune in. The station is making to the eastern US. In addition to my October loggings it was logged in Maryland yesterday. So wherever you are, check out 8101 kHz USB around 1215 UTC and see if you can hear this mystery station from Vietnam.

Don Pushes Portable Antennas Further: Loop Size, Performance, and Real-World Limits (Part 2)

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Many thanks to SWLing Post contributor Don Moore–noted author, traveler, and DXer–who shares the following post:

Two Portable Antennas for Remote DXing (Part Two)

By Don Moore

Don’s traveling DX stories can be found in his book Tales of a Vagabond DXer [SWLing Post affiliate link]. If you’ve already read his book and enjoyed it, do Don a favor and leave a review on Amazon.

In my initial comparison of the PA0RDT mini-whip and the MLA-30+ MegaLoop, the mini-whip performed best on medium wave and the lower shortwave bands, while the loop worked better on the higher bands. But, I wondered, why should the MLA-30+ be restricted to that small steel loop? The wire loops I use with my Wellbrook ALA-100LN typically range from twenty to fifty meters in circumference.

I threw a twenty-five-meter wire over a tree branch and formed it into a delta with the MLA-30+ in the bottom center. Remember, I was testing in the northern Chicago suburbs. My SDRs were completely overloaded. Medium wave was useless and I had strong MW stations all over the shortwave bands. The MLA-30+ doesn’t have the same strong-signal handling capabilities as the Wellbrook. And there are a lot of strong medium wave signals in the Chicago suburbs.

So I took that wire down and replaced it with a loop of twelve meters circumference.

That did the trick. I had lots of signals on medium wave without the overloading. Here’s what the upper end of the MW band now looked like with the MLA-30+.

For comparison, here’s the same wire loop using the Wellbrook ALA-100LN. The Wellbrook has a slightly lower noise floor but otherwise the signals are about the same.

Out of curiosity, I replaced the Wellbrook power unit with the Bias-T from the MLA-30+ but left the Wellbrook antenna head unit in place. With this hybrid setup there’s no visible difference with the full Wellbrook.

I was satisfied with my findings but I still wondered how much wire the MLA-30+ could handle. A few weeks later I ran some more tests in Kansas, where I knew the dial wouldn’t be as crowded. The MLA-30+ easily handled a 25-meter delta loop without overloading.

Two weeks after doing the Kansas tests I was at a DXpedition in rural western Pennsylvania. The MLA-30+ worked fine with a 40-meter circumference loop, other than being a tad noisier than the Wellbrook with the same wire. So how much wire you can use with the MLA-30+ components depends on how strong your local medium wave stations are.

Findings

From the SDR images above it would be easy to conclude that with the right length of wire an MLA-30+ is just as good as a Wellbrook ALA-100LN even though it is significantly cheaper. But that’s not the full picture. Back in the 1990s my Drake R-8 cost about three times what my Sony ICF-2010 did.  All other things being equal, I would say that 95% of the DX heard on the Drake could have been heard equally well on the Sony. I wanted the Drake for the other five percent.

I have no doubt that if I did a very careful head-to-head comparison of the two units under serious DX conditions on the same wire that the Wellbrook would get things the MLA-30+ couldn’t. But I suspect the difference would be around that five percent mark. I’m willing to accept that tradeoff for an effective cheap light-weight travel antenna. And the MLA-30+ is like having two antennas in one. I can use it with the steel loop in limited space situations or with a larger wire loop when I have access to some garden space with a tree. Together, the MLA-30+ and the PA0RDT make the perfect DX travel antennas.

The only thing I didn’t like about the MLA-30+ was that pre-attached coax cable. It’s not the best quality and I’d rather carry my own cable. I’m not very handy with a soldering iron in tight spaces but at our recent DXpedition my friend Bill Nollman replaced the coax with a BNC jack for me.

The MLA-30+ now looks like this when connected to a wire loop.

Finally, I should address powering the MLA-30+ via USB. While it can be connected to a spare USB port on your laptop, I found doing that sometimes introduced a tad more noise. Instead I’ve been using one of those battery packs used for recharging cellphones. Mine is rated at 6700 mAh and it can power the MLA-30+ for over 48 hours before needing a recharge. But be sure to test yours before doing any serious DXing. I’ve read that some power packs have a minimum required power draw and will automatically shut off if the draw is too low.

Another Option?

While I was finishing this article I heard about another option from my friend Guy Atkins.  This antenna is a combination of the YouLoop with a low-priced Chinese made clone of the LZ1AQ amplifier. Some users say it’s better than the MLA-30+. Guy says it works well on shortwave up to 16 meters but he hasn’t tried it on medium wave. Guy says it’s a “low price, good value” antenna. I’m traveling in Southeast Asia for the winter but will definitely have to try this antenna when I get back to the USA. So maybe there will be a follow-up article next summer.

Links

[Note: Amazon links are affiliate and support the SWLing Post at no cost to you.]

Info on ordering a quality PA0RDT from Roelof Bakker. (Other cheaper versions have had issues with quality control.)

https://dl1dbc.net/SAQ/miniwhip.html

There are various versions of the MLA-30+ and the original MLA-30. This is the version that Mark Taylor recommended and that I bought.

https://amzn.to/3MEKjPY

There are numerous YouTube videos on using and modifying both versions of the MLA-30+. This one shows how to replace the coax with a BNC jack.

https://www.youtube.com/watch?v=OAqh2Lawwdc

Here’s the Amazon link for the YouLoop/LZ1AQ antenna that Guy has.

https://amzn.to/4s1RB09

And the same antenna on Ali Express.

https://www.aliexpress.us/item/3256808527623276.html

Portable Antennas for Serious DXing: Don’s Field Tests from Parks to the Open Road (Part 1)

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Many thanks to SWLing Post contributor Don Moore–noted author, traveler, and DXer–who shares the following post:

Two Portable Antennas for Remote DXing (Part One)

By Don Moore

Don’s traveling DX stories can be found in his book Tales of a Vagabond DXer [SWLing Post affiliate link]. If you’ve already read his book and enjoyed it, do Don a favor and leave a review on Amazon.

Once upon a time, I had a traditional DX shack with an L-shaped desk and shelves of receivers, radio gadgets, and DX books. Everything I wanted or needed as a DXer was right at hand. Then I retired and was finally able to pursue my lifelong itch for serious travel. But there was no way to carry that DX shack along with me. Fortunately, modern technology was there to help. SDRs are significantly more travel-friendly than my old Sony ICF-2010 (let alone the Drake R-8). Instead of books and bulletins, my DX reference materials are websites and PDF files on my laptop.

I spend several months a year traveling internationally with just a suitcase and knapsack. That doesn’t leave much room for DX equipment. Several years ago I described my approach to vagabond DXing in an article here.

https://swling.com/blog/2019/03/radio-travel-a-complete-sdr-station-for-superb-portable-dxing/

Since writing that article in 2019, I’ve continued to work on making my portable DX shack better and more compact. Recently, I replaced the Elad FDM-S2 with three Airspy HF+ Discovery SDRs. Not only are they smaller and lighter, but I can record three different band segments at once. Next up was rethinking my travel antennas. A wire loop with the Wellbrook ALA-100LN is still, in my opinion, the best travel antenna. But the components are heavy and are now irreplaceable since they are no longer made. So over the summer, I set about testing and comparing both old and new options. But you don’t have to wander the globe for my findings to be useful to you. This can be just as helpful for DXing from a nearby park. That’s how I did my testing.

I spent the past summer staying at an AirBnB in the north Chicago suburbs. I wanted a better location for testing so I checked out parks in the area and finally settled on Preserve Shelter B (42.26797, -87.92208) at the Old School Forest Preserve, east of Libertyville in northern Illinois. The shelter was entirely wood, with standard asphalt shingles (rather than steel), and had no nearby power lines. I made four daytime DXpeditions there to do some utility DXing and to run my tests. Here’s a photo of my setup.

I decided I should rerun the tests at least one other location. So while driving across the US in mid-October, I stopped for a few hours one morning at Park Shelter A (39.11144, -94.86629) in Wyandotte County Park, just west of Kansas City, Kansas. There, I just had a minimum setup.

The Antennas

So, what were the antennas I was testing? The first was the tried-and-true PA0RDT mini-whip from Roelof Bakker. The PA0RDT is described in my 2019 article and is probably the most portable quality antenna you can get. To power it I use a battery box and eight rechargeable lithium-ion AA cells.

 For the traveling DXer, setting up the PA0RDT is as easy as it comes. I just attach the coax cable and throw it over a support, such as a picnic shelter beam or a tree branch.

But I’ve always believed that the best antenna is another antenna. That is, every antenna works differently, and therefore the more options you have, the more likely you will have something that works well in any situation. So if I wanted to leave the Wellbrook at home, what might complement the PA0RDT? I contacted my friend Mark Taylor, who I knew had a large collection of the various inexpensive Chinese-made amplified loops. With his help, I settled on the MLA-30+ MegaLoop from DmgicPro.

This antenna consists of a steel wire loop that connects to terminals on the amplifier box. The amplifier has a ten-meter coax cable, which in turn is connected to a small bias-T power supply, which gets its power via a USB connection. The MLA-30+ is designed to be used in a permanent installation with some sort of vertical support, such as a PVC pipe. Some users replace the wire loop with copper tubing.

Those options aren’t practical for me, and simply hanging the antenna from the top would cause the steel loop to stretch and deform. So I came up with the idea of tying a strong cord from the top to the bottom of the loop so that the cord, and not the loop, bears the weight. To hang the antenna, I throw the cord over the support, attach the antenna, and then pull it up into place. That works well if you have rear support to hold it in place, such as the beams of a picnic shelter.

It’s a bit more difficult to mount the MLA-30+ in a tree.

Comparing the Antennas

I ran comparisons between the antennas several times at Old School Forest Preserve and then again at Wyandotte County Park. The results were practically the same every time. The images below were made at Old School unless otherwise stated.

The PA0RDT was designed to be a good performer on longwave and medium wave. Unsurprisingly, it shows a lot of signals on the upper end of the medium wave band, even during the daytime. Except for being non-directional, the PA0RDT is an excellent MW antenna.

The MLA-30+, on the other hand, isn’t good for much beyond hearing the strongest local signals on medium wave.

When I ran these tests in the late morning, WWV on 5 MHz was the only signal in the 60-meter band. It had a very listenable signal on the PA0RDT.

But on the MLA-30+, WWV was barely there.

Likewise on 49 meters, CFRX on 6070 kHz was very clear on the PA0RDT but barely listenable on the MLA-30+. But when I moved up to 31 meters, the difference between the antennas mostly disappeared, as in these images made in Kansas. The PA0RDT is top and the MLA-30+ on the bottom.

On 25 meters, the PA0RDT is picking up a lot of noise and the signals are not that strong. Nor were signals very strong on 19, 16, 0r 13 meters.

However, on 25 meters with the MLA-30+ there isn’t much noise and the signals are booming in. And 19, 16, and 13 meters likewise had strong signals.

So the PA0RDT is clearly the best antenna for MW and the lower shortwave bands, but it doesn’t do as well on the higher bands. This wasn’t a surprise to me as I’ve always felt that the PA0RDT underperformed above nine or ten Megahertz. The MLA-30+ was abysmal at the lower frequencies but worked better or just as well in the middle and higher shortwave bands. The best antenna is another antenna. Each one performs better in different situations. But I couldn’t help but wonder … was the problem with the MLA-30+ that small steel wire loop?

Look for Don’s Part 2 article next weekend on the SWLing Post!

From Missouri to Oklahoma: Discovering America’s Secure Nets on 5140 kHz

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Many thanks to SWLing Post contributor Don Moore–noted author, traveler, and DXer–who shares the following post:

Icom IC-756 Pro Transceiver DialThe Missouri and Oklahoma Secure Nets

By Don Moore

Don’s traveling DX stories can be found in his book Tales of a Vagabond DXer [SWLing Post affiliate link]. If you’ve already read his book and enjoyed it, do Don a favor and leave a review on Amazon.

I’m always looking for new stations to add to my logbook, and the more unusual, the better.  So I was intrigued by a pair of messages in the Utility DXers Forum (https://www.udxf.nl/) email group in mid-August. Steve Handler posted a list of emergency station call signs from the state of Missouri that he found on the web in a 2014 emergency plan document. Then Jack Metcalfe responded that the last time he had checked, in early 2024, they ran a regularly scheduled net on 5140 kHz.

I immediately sent an email to Jack to find out more. He answered that on Wednesdays the Oklahoma State Secure Net had been doing a check-in at 0900 local time and that the Missouri State Secure Net followed at 0930 local time. Both of these started on 5140 kHz and then moved to 7477 kHz.

Going After the Secure Nets

I was spending my summer at an Airbnb in the north suburbs of Chicago. It wasn’t a good place to DX from, but I had already found a good listening site at the Old School Forest Preserve near Libertyville, Illinois. I began a series of regular Wednesday morning listening sessions. I knew that this wasn’t the best time of year for reception on lower frequencies, but I wanted to give it a try.

All I got from the Oklahoma net was a few very weak and unreadable signals. From the Missouri net, I got two loggings of the net control station, WNBE830, and of WQKX373 in St. Charles County. Two other Missouri stations did check in, but they were too weak for me to copy the call signs. They did say that the net is only on the first and third Wednesdays of the month. And there was nothing on 7477 kHz, so they apparently stick to 5140 kHz only now.

Recording of WNBE830 as heard on 5140 kHz at 1430 UTC on 03 September 2025, as heard in Old School Forest Preserve:

In mid-September, I left Chicago to visit my daughter in western Colorado. While I was planning my return drive back east along I-70, I realized that I would be spending the night of Tuesday, October 14, somewhere around Kansas City. And that meant I would be in the area the next morning for the third Wednesday of the month. I made plans for another mini DXpedition.

I found a hotel in the west suburbs and the next morning headed to a picnic shelter in nearby Wyandotte County Park for another remote DX session with my Airspy HF+ Discovery SDRs and PA0RDT mini whip. It was an excellent location. I logged five stations participating in the Oklahoma net. During the initial chitchat before the roll call, it was mentioned that some of the participants were at a conference. I might have gotten more stations if it hadn’t been for that. The Missouri net, on the other hand, did not make an appearance even though it was the third Wednesday.

Recording of roll call in the Oklahoma State Secure Net on 5140 kHz at 1407 UTC on October 15, 2025, as heard in Wyandotte County Park.

How To Log the Secure Nets

I didn’t hear as many new stations as I had hoped, but then I was listening in late summer and early autumn. There had already been several hours of daylight before the net started, which isn’t the best for propagation on the lower shortwave frequencies. The northern hemisphere is moving into winter, and as that happens, sunrise times will move later. And that will allow 5140 kHz to be heard at greater distances during the timeslot these nets are on. If you can hear WWV on 5 MHz in mid-morning in mid-winter at your location, you should have a chance at these.

The nets are on at 0900 and 0930 local (Central) time. When I was tuning in, that was 1400 and 1430 UTC, but when the US goes off of Daylight Savings Time on November 2nd, that changes to 1500 and 1530 UTC. From what one of the Oklahoma stations said, it sounded like the Oklahoma net is on every Wednesday. The Missouri net did say only first and third Wednesdays, but according to Jack Metcalfe, it was weekly some years ago. And for some reason, they weren’t on the third Wednesday of October.

I’m going to be spending the next four months traveling in Southeast Asia, so I won’t be DXing these again until I return to Chicago for a short visit in March. But hopefully some of you reading this in North America will try to hear these networks, too. Given that there is some question as to which Wednesdays these networks take place, I suggest setting up your SDR to make a spectrum recording including 5140 kHz every Wednesday at 1400/1500 UTC for the next few months. And let me know what you hear by dropping me a message to Don AT DonMooreDXer DOT com. If I get enough good information, I’ll put together an update to this article.

And that brings up something else. Do you know of any other regularly scheduled utility voice networks on shortwave like this one? Over twenty years ago, the US Army Corps of Engineers and the Federal Aviation Administration had weekly voice nets, but those are long gone.

Please post what you know in the comments or send me an email to the above address.

Oklahoma Secure Net Stations

On logs going back to 2005, these are the stations that Jack Metcalfe has heard participating in the net.

  • KNBV428 Santa Fe, NM
  • KNFG267 Oklahoma City, OK (normal net control)
  • KNGR728 Rush Springs, OK
  • WGY926 Oklahoma City, OK
  • WNBM839 Stillwater, OK
  • WNCH624 Department of Emergency Management, Tulsa, OK
  • WNPV700 Durant, OK
  • WNUW211 Oklahoma City, OK
  • WNUW212 Department of Emergency Management, Shawnee, OK
  • WNUW213 Department of Emergency Management, Altus, OK
  • WNUW215 Ponca City, OK
  • WNUW216 Oklahoma City, OK
  • WNUW217 Ardmore, OK
  • WPBV938 Beaver, OK (Beaver County EOC)
  • WPFY721, Oklahoma Emergency Management Agency EOC at the National Guard Armory, Seminole, OK
  • WQSY836 Byng, OK

My logs include three more stations either participating in or being unsuccessfully called.

  • WQYW833 Unknown location
  • WQZT582 Broken Arrow
  • WSHM692 Oklahoma City

Missouri Secure Net

Stations Jack Metcalfe has logged.

  • WNBE830 Ike Skelton Training Center, Jefferson City, MO (net control)
  • WNUW240 Missouri EMA, Jefferson City, MO
  • WQKE203 Missouri Dept of Transportation, Jefferson City, MO
  • WQOI753 Missouri Dept of Transportation, Hannibal, MO
  • WQOI754 Missouri Dept of Public Safety, Sikeston, MO
  • WQOJ557 Missouri State Police Radio Shop, Jefferson City, MO
  • WQOL350 Missouri Dept of Public Safety, Chesterfield, MO
  • WQOL459 Missouri Dept of Transportation, Lee’s Summit, MO

I heard one additional station:

  • WQKX373 St. Charles County, MO

Next listed are the stations Steve Handler found listed in the 2014 edition, Appendix 2, Section 2.22 of the 2014 Emergency Operations Plan. This plan was publicly posted by the City of Battlefield at the following URL:

https://core-docs.s3.us-east-1.amazonaws.com/documents/asset/uploaded_file/4319/CBM/3591786/complete_emergency_operations_plan.pdf

  • KNNT320 Boonville, MO
  • KNNT321 Greenwood, MO
  • WNUW238 Battlefieldd, MO
  • WNBE824 Jackson, MO
  • WNBE825 Rock Port, MO
  • WNBE826 Lee’s Summit, MO
  • WNBE827 Macon, MO
  • WNBE828 St. Louis, MO
  • WNBE829 Springfield, MO
  • WNBE830  Jefferson City, MO
  • WNBE831 Poplar Bluff, MO
  • WNBE832 St. Joseph, MO
  • WNBE833 Willow Springs, MO
  • WNBE834 Raytown, MO
  • WNBE835 St. Charles, MO
  • WNBE836 Hillsboro, MO
  • WNBE837 Neosho, MO
  • WNUS448 Union, MO 64084
  • WNWU734 St. Joseph, MO
  • WPCY526 Kansas City, MO
  • WPBN258 Kirkwood, MO
  • WNZJ459   Belton, MO
  • WPES740  Camdenton, MO
  • WPGA369 Fort Leonard Wood, MO
  • WPKX561 Hermann, MO

According to the same document, the net is authorized to use the following frequencies. Under 7477 kHz, there is a note that the station uses 1000 watts during the day and 250 watts at night.

2326, 2411, 2414, 2419, 2439, 2463, 5140, 5192, 7477, 7802, 7805, and 7935 kHz.

A big thanks to Jack Mecalfe for his assistance with this and to Steve Handler for making the initial post that drew my interest. 

Taming the Noise: Don Moore’s Simple, Cheap Filter Solution for Traveling DXers

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Many thanks to SWLing Post contributor Don Moore–noted author, traveler, and DXer–who shares the following post:

A Cheap and Simple Noise Filter

By Don Moore

Don’s traveling DX stories can be found in his book Tales of a Vagabond DXer [SWLing Post affiliate link]. If you’ve already read his book and enjoyed it, do Don a favor and leave a review on Amazon.

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.  It was a simple setup but it worked very well. Do you know what I didn’t 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.

Times have changed, haven’t they? What DXer doesn’t 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’t DX anymore.

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’s no way of knowing what the noise level will be until I get there.

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.

No, these weren’t designed for radio use. And they aren’t a miracle solution that will eliminate all the noise that plagues DXers. Sometimes they’re no use at all. But I’ve 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’t go anywhere without two of these packed in my mobile DX shack.

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.

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’s hard to pick out WWV on 5 MHz from all the noise peaks. In the second image the filter hasn’t totally eliminated the noise, but WWV’s signal is now strong and clear.

The noise was nearly as strong on 49 meters but the filter almost totally eliminated it. CFRX’s signal on 6070 kHz was slightly weaker with the filter, but it was significantly more listenable without the noise.

Which frequencies noise affects can vary between locations. At that park the noise was gone above about 11 MHz.  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.  The noise there was bad in the middle shortwave bands, such as in the 25 meter band.

But the filter did a good job cleaning it up.

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.

These filters should work with any coax-fed antenna. I’ve 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).  I’m not sure what the impedance on these is, but I’ve used them with both 50- and 75-ohm coax cable.

Sources of the Filters

An Internet search for “CCTV Ground Loop Isolator” 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.

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.]

A Few More Ideas

At just a couple dollars each, every DXer should have a few of these filters in their shack. But types of noise vary and at several places I’ve DXed from using one of these filters made no difference at all. When that happens I have a few other solutions to try.

The first thing I try is to either move the antenna or, if it’s directional, to point it in a different direction. On several occasions that’s all it has taken to totally eliminate what at first seemed like an impossible noise problem.

If the noise is coming in through the power lines, unplugging the laptop and DXing off of battery power might do it. (I only use SDRs powered off the USB connections on my laptop.)  If you do that, be sure to unplug the cord from the outlet and move it away from the wall.  If you unplug the cord from the laptop and leave the other end plugged into the outlet, it may act as an antenna and radiate the noise from the power lines into your SDR. And, yes, I learned that lesson the hard way!

Do you have any interesting experiences or solutions to the DX noise problem? Please leave them in the comments section. 

New SDR Recordings from Peru and Brazil Now Available via Don Moore

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Our good friend and longtime contributor Don Moore has just updated his extensive SDR recordings archive with new files from his recent travels in South America. These latest recordings—captured in Peru (February) and southern Brazil (May)—are now available to explore and download.

Don writes:

I have a webpage where most of the SDR recordings from my travels are available for download. I just added files made in Peru in February and in the far south of Brazil in May. This archive is mostly medium wave. I hope they give other DXers a chance to hear what the dial sounds like in other parts of the world. They could also be useful as a way to compare possible IDs, ads, and other programming with what you hear in your own DXing.

You can browse and download the recordings directly via Don’s archive here:

https://www.donmooredxer.com/logs/loglinks.html

Many thanks, Don, for sharing these with the SWLing Post community!

Don Moore’s Photo Album: Guatemala (Part Seven) – Radio Maya de Barillas

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Image: Radio Maya via Facebook

Don Moore’s Photo Album:
Guatemala (Part Seven) – Radio Maya de Barillas

by Don Moore

More of Don’s traveling DX stories can be found in his book Tales of a Vagabond DXer [SWLing Post affiliate link]. If you’ve already read his book and enjoyed it, do Don a favor and leave a review on Amazon.

Given the subject of this final part you might assume that I eventually did make it to Barillas and get to visit Radio Maya. I wish it were so, but no. When writing part six of this series I tried to find a few interesting links about Radio Maya to include. I came across a 38-minute video about the history of the station issued on its 50th anniversary in 2012. The video is a series of still photos (most very old) narrated in Kanjobal.

Actually I’m assuming that it’s Kanjobal as that is the Mayan language spoken in Barillas. I don’t speak Kanjobal, but the Mayan languages use Spanish for numbers, dates, and modern ideas such as technical terms. Between the Spanish words and the context provided by the photographs, I was able to somewhat understand the video. Instead of expecting you to watch the 38-minute video, I’ve copied the most interesting pictures below. (I don’t think you want to see pictures of all the people involved over the years.)

Beginnings

There had been an Evangelical mission in Barillas since the mid-1950s. The name of whoever decided to put a radio station in Barillas is lost to history. But, like Father John Rompa of the Catholic station La Voz de Nahualá, they realized that radio was the best way to reach the Mayan people scattered across remote mountain towns and villages. Also lost to history is why they picked a place as remote as Barillas. Not only was the town at the end of the road, but in the early 1960s the last stretch of road wasn’t even drivable. Hauling in equipment for the new broadcaster was a challenge.

Here a man carries part of the transmitter on his back:

The transmitter eventually arrived in Barillas on an oxcart:

In these next two pictures about two dozen men haul the generator over a rough stretch of road:

The original building in 1962:

The next step was putting up the antenna. Here villagers prepare to erect a wooden pole as a center support for the antenna wires:

One of two shorter poles to hold up the lower ends of the wire:

When the pole was in place a very brave (or foolhardy?) man climbed to the top to attach the wires:

The finished tower. The antenna wires, attached at the top, aren’t visible. The lower wires are for support:

From its beginnings until the late 1970s, Radio Maya de Barillas only broadcast on 2360 kHz with this 250-watt transmitter. Later a one-kilowatt transmitter was added for 3325 kHz.

Installing the generator:

The Radio Maya studio in the 1960s:

Getting Bigger

In 1969 a plot of land was purchased on the edge of town and over the next three years a new building was constructed with help from American missionaries. Continue reading →