Category Archives: Mediumwave

WNAM Final Broadcast and DX Test Announcement: December 30-31, 2025

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The following announcement was shared by Loyd Van Horn of DX Central:

FOR IMMEDIATE RELEASE

1280 – WNAM DX Test Announcement

Dec 27, 2025

The Courtesy Program Committee (CPC) of the National Radio Club (NRC) and the International Radio Club of America (IRCA) announces a special DX Test for distant listeners for radio station WNAM on 1280 kHz in Neenah-Menasha,WI. The test is scheduled for Tuesday, December 30th and Wednesday, December 31st starting at Midnight local Central Standard Time through 5:05 AM Central Standard Time (This equates to 0600 to 1105 UTC on 30 December and 31 December).

This test is scheduled to run for 2 minutes after ABC News at the top-of-the-hour each hour from Midnight to 5am local Central time. ABC News runs from :00-:03 after the hour. The DX Test will run from :03-:05 after the hour, each hour of the window.

These test transmissions are being broadcast in conjunction with the final days of broadcast of WNAM. WNAM is scheduled to cease broadcast operations at 11:59 PM Central Time on December 31st.

These test transmissions are a way to honor the history of WNAM in its service to the community as well as provide an opportunity for DXers to hear WNAM one last time – or possibly the first time!

The test will consist of an assortment of classic station jingles, sweep tones, voice IDs, morse code and other sounds.

WNAM will be operating at their daytime power/pattern for the duration of the test events.

In addition, listeners/DXers are invited to tune in WNAM’s special 3-hour farewell broadcast on Wednesday, December 31, starting at 9:00 PM Central Standard Time. This will include a “recreation” of the station’s glory years as “Blue 128” complete with airchecks from previous on-air staff.

RECEPTION REPORTS & QSL REQUESTS

All reception reports will be verified through the station directly with a special QSL that was developed for the occasion. Reception reports along with MP3 recordings or .MP4 video recordings of your reception should be emailed to:

[email protected]. Please be sure to use the subject line: “WNAM 1280 DX TEST RECEPTION REPORT.”

The following are recommendations are in effect in order to expedite processing and receive a QSL verifying your report:

    • Reports via email only – this is required. An MP3 file attachment of your reception (best reception) or an MP4 video clip are preferred. While written descriptions will be considered along with the recording, they may not suffice alone for verification.
    • Reports must be submitted within 30 days of the test.
    • The report must include your name, location, and return email address, clearly grouped together at the top of the verification request.
    • Please also include a description of your receiver, antenna, and any interference noted.
    • If you use a remote SDR to receive the test, you must clearly indicate that in your verification request. We will only accept one such report per DX’er. You cannot log the test on multiple remote SDRs and request multiple verifications.

The IRCA/NRC CPC would like to thank the owners and staff of WNAM}, Steve Edwards and CPC member Loyd Van Horn for helping to arrange the test.

Good luck to all DXers!

About the CPC

The Courtesy Program Committee (CPC) is a cross-functional group comprised of members of both the National Radio Club (NRC) and International Radio Club of America (IRCA) for the purpose of coordinating and arranging DX Tests with AM radio stations. These DX tests both allow radio stations to conduct valuable equipment tests on their transmitter and audio chain as well as enable DX hobbyists to receive the testing station from greater distances than would normally be possible. The CPC membership consists of: Chairman Les Rayburn, Paul Walker, George Santulli, Joe Miller and Loyd Van Horn.

For radio stations interested in coordinating a DX test with the CPC, please visit the following Web site for more information:

https://amdxtest.blogspot.com/

For more information on the types of content heard during a DX test, the video “An introduction to DX Tests” is available at DX Central:

https://www.youtube.com/watch?v=NQX_zmEC4fY

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!

Check Your Time with the LM Chime

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by Dan Greenall

Shades of the 1970’s.  Commercial AM radio (in English) the way it used to be. Heavy on nostalgic music from the 1960’s to the 1990’s, plenty of good old style jingles, and of course, the LM chime every hour.

Decades ago, the “LM” used to stand for Lourenco Marques Radio as the station was based in this city in Mozambique. Today, it is Lifetime Memories Radio, and broadcasts to Maputo and the surrounding area, where it can be heard on 87.8 FM. The station also broadcasts on 702 kHz medium wave from a transmitter near Johannesburg, South Africa, and can be heard worldwide via Kiwi SDR or online stream here   https://lmradio.co.za/

In addition to the live stream, be sure to read about the rich history of the station that began in 1936. The station was shut down in 1975 when Mozambique gained independence, but has re-emerged in the 21st century.  A visit to the LM Radio museum is well worth the trip.  https://lmradio.co.mz/history/

In 1973, I was able to hear Radio Clube de Mocambique on 4855 kHz shortwave from here in Canada.  If you listen closely, you can hear the LM chime.

Give them a listen, but first, check out these sample recordings made between November 27 and December 8, 2025, through a Kiwi SDR located near Johannesburg:

2025-11-27:

2025-11-28:

2025-11-28:

2025-11-29:

2025-12-04:

2025-12-08:

Giuseppe’s Clever Homebrew Ferrite Antenna for MW and SW Listening

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Screenshot

Many thanks to SWLing Post contributor, Giuseppe Morlè, who writes:

Dear Thomas,
I’m Giuseppe Morlè, IZ0GZW, from Formia in central Italy on the Tyrrhenian Sea.

This is one of my builds from a few years ago: the T Ferrite antenna. It’s a minimal antenna designed mainly for mediumwave, but it also performs well on shortwave.

Inside the tube at the top are two 12 cm ferrite rods with 32 turns of telephone wire wrapped around them—this section is for mediumwave. Then, on the outside of the tube, I added four more turns for shortwave. A variable capacitor of about 1000 pF completes the circuit.

Shortwave is activated with an alligator clip. When the clip is removed, only the mediumwave section is active.

I tested this antenna with my old Trio 9R-59DS from the 1970s—a tube receiver still in perfect condition. To my pleasant surprise, the receiver paired beautifully with the antenna.

These tests were done on mediumwave in the early afternoon yesterday while it was still light outside. With the antenna placed above the receiver inside my shack, I was able to receive stations from across the Mediterranean basin and Eastern Europe, even in areas where the sun had already set. I really enjoy testing this antenna before evening, and I’m very satisfied with its performance.

You can see the results in this video on my YouTube channel:

I hope this will be of interest to the friends in the SWLing Post community.

Best regards to you and to all,
Giuseppe Morlè, IZ0GZW

We always enjoy checking out your homebrew antenna designs, Giuseppe! Thank you!

Ultra Convenient, The Benefits of WavViewDX: Visualizing Reception Conditions (A Totsuka DXers Circle Article by Satoshi Miyauchi)

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Many thanks to SWLing Post contributor Nick Hall-Patch, who has kindly provided a translation of this article from the Japanese-language publication PROPAGATION by the Totsuka DXers Circle (TDXC). In this piece, Satoshi Miyauchi explores how WavViewDX can revolutionize SDR analysis by making propagation and reception conditions instantly visible–and shares some remarkable reception examples.

“Ultra” Convenient, The Benefits of WavViewDX: Visualizing Reception Conditions 

by Satoshi Miyauchi

After recording bands using SDR’s such as Perseus or HF Discovery, I was informed by Kazu Gosui via email of a new program that’s “ultra” convenient for analyzing them. When monitoring in real time with Perseus, I have a general memory and notes of what was received at what time.  However, when recording reception data without real-time monitoring, such as during nighttime hours, verifying and analyzing the data across all frequencies takes time. Knowledge and intuition about where to listen are also important elements. While all of this is a skill, I believe that previous tools have been unable to provide a comprehensive view of the day’s conditions. Since I started using WavViewDX, I’ve been using it every morning, efficiently analyzing the SDR recordings I’ve collected.

By the way, recently I’ve been using a timer (the “Scheduler” of SDR Console) to check if the TWR-Africa signal transmitted from Benin, West Africa, is reaching me in the middle of the night. My analysis showed a significant reduction in the time required for confirmation that TWR-Africa was being received before and after WavViewDX was installed, and I’d like to share this with you.

Just to be clear, this article is not intended to be a tedious rehash of the user manual. Rather, it is intended to provide useful, pinpointed tips for use.

  1. I’ll introduce a method I think might be best based on my current setup.
  2. I’ll share some reception reports from my recent morning routine.
  3. I’ll touch on the mysteries of radio wave propagation, a realization I believe is unique to WavViewDX.

But first, a word about WavViewDX: seeing is believing. As shown in the sample image in Figure 5, it visually displays the status of stations received at each frequency, using green bars or white lines, in chronological order, from the lowest frequency band (left) to the highest (right). You can even customize it to analyze North and South America at 10 kHz intervals for TP reception.

The author is Reinhard Weiß from Germany (please see accompanying related articles).  It is an incredibly easy-to-use and intuitive software. Once you start using it, you’ll definitely want to keep it.

Figure 5

First, let’s assume you’ll be importing and analyzing data into WavViewDX.

1.) Timer Reception Tips, Using SDR Console

This is a backward-thinking approach based on the fact that WavViewDX can import files in “folders.” The golden rule is simply to store all files from a single session in a single folder. I’ve been using SDR Console as my primary SDR program for a while now, so when I register a scheduler (for timer scheduling), I click “Add date (yyyy-mm-dd) subfolder” under “Folder”, in Figure 6. This allows me to import the entire folder of recording files from that day into WavViewDX, saving me a lot of time. WavViewDX has a “Select Whole Folder” button, which allows me to import files into WavViewDX with a single click (Figure 7). How amazing! Incidentally, I set up bandwidth recording files to be stored in separate 1GB files. The moment I wake up, the files are instantly imported into WavViewDX, allowing me to quickly check the conditions from midnight to dawn before work.

Figure 6

Figure 7

2) TWR-Africa Reception Recording

Even on shortwave, it’s rare to see signals from Africa, let alone on mediumwave. Until a few years ago, I thought this was impossible. However, I discovered that I could record pre-dawn signals from Africa on my home K9AY loop, including the VOA of the Sao Tome and Principe relay on 1530kHz, as well as the famous TWR Africa (Benin) on 1476kHz. Of course, it’s not easy to receive signals every day, so I was not motivated to record them regularly However, after installing WavViewDX, I was able to easily grasp the pre-dawn conditions, and I set up a scheduler to record as many times as possible every day.

Then, one morning, right around 3:30 AM, on the morning of the March vernal equinox, I noticed a very clear bar on the 1476kHz using WavViewDX (Figure 8). By working in conjunction with WavViewDX, it automatically checks offsets in exact carrier frequency being received against the MWList database, and the > mark quickly lights up in WavViewDX, indicating that it’s TWR Africa! I was surprised when I heard the audio. I was impressed by the exceptionally clear reception. There was a slight beat, and it seemed like at least one other carrier was also in the mix. How such clear audio managed to reach and be heard across nearly 13,300 km as the crow flies is a mystery, but it’s still a moving experience.

Figure 8

I asked @lft_kashima LFT Kashima Fishing Radio, who regularly posts information on X, and he said that the signal wasn’t as good on that day at his location. Since we’re both in the Kanto region and a little farther apart, perhaps that’s the problem, or perhaps it’s just the antenna. He uses a north-south loop antenna, while I use a vertical AOR SA-7000.

While I don’t know the full reason or answer, one possible guess: – Wasn’t the arrival direction north-south? – Did it arrive through a duct somewhere? However, there’s no way to know why the duct ended up at this receiving point. It’s a wonder that I was able to receive such a DX station at this point in the solar cycle, when the number of sunspots is almost at its maximum and the A/K Index was far from calm. This makes daily reception all the more meaningful. It’s a moment that makes me admire nature, the work of radio wave propagation.  I was able to receive this station again in April, and the links to those two results from 1476kHz – TWR Africa are below:

3) The Mysteries of Radio Wave Propagation Discovered Only with WavViewDX

WaveViewDX already clearly shows the reception status on the vertical time axis, but just before the vernal equinox, a phenomenon in which the propagation conditions deteriorated simultaneously across multiple frequencies occurred, albeit for a short period of time. (Audio Sample https://youtu.be/XhXSQFiGQeo) What is this? Figure 9 shows the actual situation at my location on March 17, 2025, after 18:00 UTC.

Figure 9

  1. 1278kHz JOFR Fukuoka RKB Mainichi Broadcasting System 50kw (about 900km distance, 245°)
  2. 1287kHz JOHR Sapporo HBC Hokkaido Broadcasting System 50kw (about 1000km distance, 340°)
  3. 1332kHz JOSF Nagoya Tokai Broadcasting System 50kw (about 270km distance, 270°)

(*Note: The leftmost bar (1242kHz in the Kanto region) is attenuated with a notch filter)

One of the benefits of WavViewDX is that it visually showed the simultaneous drop in signal strength from domestic and international stations, which had been arriving almost smoothly until 18:00 UTC.

I asked Perplexity AI and searched the literature. These possibilities were listed:

“Regarding the phenomenon of simultaneous attenuation of radio signals in all directions for several minutes during nighttime propagation in the medium frequency band (MF band),” it is believed to be primarily caused by the combined effects of the following factors: –

  • Ionospheric Variation Mechanism Sudden E-Layer (Es-Layer) Formation A localized increase in electron density in the upper E-layer of the ionosphere (at an altitude of 100-120 km) at night. This thin ionosphere strongly reflects signals, blocking the normal F-layer reflection path. One measurement data showed signal attenuation of up to 20 dB when the Es layer occurred.
  • F-layer altitude fluctuations: When the F layer (altitude 250-400 km), the main nighttime propagation path, rapidly rises due to thermal expansion, the reflection angle changes, creating a “propagation hole” that causes signals to deviate from the receiving point.
  • Earth’s magnetic field fluctuations disrupt the electron distribution in the ionosphere, causing a sudden increase in absorption.
  • Instantaneous changes in solar activity: The emission of X-rays and charged particles associated with solar flares suddenly changes the electron density in the ionosphere, destabilizing the reflection coefficient and resulting in short-term propagation loss.

Although it was able to provide various possible explanations, I was unable to perform any further verification of these answers myself.

These English translations were prepared for IRCA’s DX Monitor, and are used with the kind permission of  IRCA as well as of the authors and the editor of the Totsuka DXers Circle publication, PROPAGATION.

An Introduction to WavViewDX SDR Playback Software (A Totsuka DXers Circle Article by Kazu Gosui)

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Many thanks to SWLing Post contributor Nick Hall-Patch, who has kindly provided a translation of this article from the Japanese-language publication PROPAGATION by the Totsuka DXers Circle (TDXC). In this piece, Kazu Gosui introduces WavViewDX, an impressive SDR file playback and analysis tool developed by Reinhard Weiß of Germany.

About WavViewDX, SDR File Playback Software

by Kazu Gosui

Introduction

“WavViewDX,” developed by Reinhard Weiß of Germany, is SDR file playback software. It maps the received signals from SDR-recorded files into bar graphs, with time on the vertical axis and frequency (channel) on the horizontal axis, for each of the following channel separations: medium wave (9/10 kHz), short wave (5 kHz), and FM (50/100 kHz).  Clicking the cursor (blue crosshair) plays the received audio. By “visualizing the received signal” through mapping (see also the separate article by Satoshi Miyauchi), you can see at a glance the start and end times of broadcasts, fade in, fade out, channels you should listen to, and channels you don’t need to listen to.

Basic Usage and Screen Description

First, download and install WavViewDX from the WavViewDX webpage (https://rweiss.de/dxer/tools.html). The latest version is version was 1544 as of June 8, 2025, when this was written, but version 1662 is available in October 2025. When you launch WavViewDX, the Main Window (Figure 1) will appear, showing Analysis View, the Operation/Settings Panel, Logbook and Database.

Figure 1

To play back recorded files, you must import them. Click Import to display the Import SDR Recording settings screen. Source files can be selected as single or multiple files, or by folder. Set the reception location, time, channel separation, etc., and begin importing. A progress percentage will appear, and green and white bar graphs will appear on the Analysis View screen. Hovering the cursor over a bar graph and clicking will display a red circle, and the audio recorded for that channel and time will play. Scrolling the mouse will allow you to zoom in and out of the Analysis View.

When you import, a WVD format file is created. Once you’ve imported the files, you can simply load the corresponding WVD file at another time, and the files will be available to play immediately.

In addition to Import and Load, the following settings are available at the top of the Main Window.

  • Analysis: Allows you to select the file/folder and frequency separation when importing.
  • Carrier Views: Displays offset frequencies to identify and estimate the received medium wave station.
  • Database: Links with the MWLIST webpage (https://www.mwlist.org/ul_login.php) to identify and estimate the received medium wave station.
  • Logbook: For documenting stations heard, along with creation of audio recordings during playback.
  • More: Allows you to set multiple options, such as manual tuning and contrast setting.
  • Setup: Allows you to set the sound device and select the file format for recording audio clips during playback.
  • About: Allows you to select the software version, Help, etc.

The Main Window also displays the frequency list linked to the aforementioned Database and the Logbook.  The database frequency list can be selected by region, such as Europe or East Asia. The Logbook allows you to record reception records and associate recorded audio files.

The right side of the Main Window contains the operation and settings panel. At the top are the Frequency Display and Spectrum View. Hovering the cursor over Spectrum View allows you to select PBT (Pass Band Tuning) and NOTCH.

Below these are:

  • Spectrum Zoom (x1, x2, x4), which expands the spectrum;
  • Bandpass Bandwidth Presets ([2.5] etc.), which change the reception bandwidth;
  • Player Time Controls (Play/Pause; -30s etc.), which control the playback time;
  • Carrier View, which displays the offset frequency; (+/- 30Hz, and can be shifted above and below the nominal .000 frequency)
  • Demodulator Modes, which change the reception mode.

(Keyboard shortcuts are available for the above functions.)

  • The AF Highpass Filter adjusts the audio frequency passband to improve intelligibility.
  • The Spike Filter reduces popping during reception.
  • Phasing combines two synchronized recording files to reduce same-frequency interference and noise.
  • NCE (Neighbor Channel Eliminator) reduces interference from adjacent channels.
  • Binaural allows you to select the sideband of the AF output during playback.
  • The AF Audio Recorder allows you to record by clicking during playback. Recording formats include WAV, FLAC, and MP3.

As you can see, there are so many features it’s impossible to introduce them all. Detailed adjustments to each function make it even easier to use; it may seem tedious at first, but give the features a try. The user interface is intuitive, so you’ll quickly get used to it. If you’re unsure how to use something, just press the F1 key and refer to the Help.

Actual Usage 

Let’s try it out. The import settings are set to MW 9+10kHz Channel Analysis Configuration. Configuration, and other settings are set to default. (editor’s note:  “SDR Calibration” allows the use of reference carrier frequencies in the data, for those SDRs without a frequency standard, so that each carrier frequency in the passband will be displayed accurately.)   Once the import is complete, a bar graph will appear. Figures 2 and 3 show the analysis view of the actual file import from early May 2025, during the Hachijojima DXpedition showing evening reception; time is UTC.

Figure 2

Figure 3

9kHz separation is used in Figure 2. You can hear the audio from 630kHz at the time indicated by a circle. Black areas of the bar graph indicate no signal, while white to green indicates good signal reception. If you miss an ID during reception, press the up arrow key to rewind the time by 5 seconds and listen again.   Click Recording to record the ID.

As you can see, the bar graph color changes from black to white and then white to green over time. This indicates that as the day turns from daytime to evening and then nighttime, channels that previously had no reception begin to receive broadcasts. Sunset on this day was 9:29 UTC (18:29 JST), and the received signal fade in was between 8:30 UTC (17:30 JST) and 9:15 UTC (18:15 JST).

Next, click Analysis and switch to MW 10kHz channel analysis. The Analysis View after switching is shown in Figure 3. This shows the reception status with 10kHz separation. Most channels are black, with a few white spots. There is very little green. In this image, there are certainly no 10kHz channels with good audio, but by clicking on the white, we can see some with faint English talk and music. I checked the database and found that these channels appear to be Hawaiian stations (see orange circle marks in Figure 3) that have been active since around 8:30 UTC.

Also, Latin music was heard on 1230 kHz (Orange circle in Figure 3). This may be Radio Dos from Argentina. By visualizing reception status like this, I was able to determine where to listen and where not to listen. During the Hachijojima expedition in May, I was blessed with outstanding reception conditions from the evening through the early morning hours of the following day, and was able to track 187 overseas medium wave stations, including 165 in Australia, 5 in New Zealand, 2 in Papua New Guinea, Solomon Islands, Tonga, Marshall Islands, Kiribati, Palau, Fiji, Tuvalu, Indonesia, and the Philippines, achieving significant results. Playback and analysis took about a week, which was shorter than usual, thanks to WavViewDX.

Summary 

As mentioned above, WavViewDX has proven to be an efficient tool for analysis, allowing users to discover previously unnoticed stations. Since it can play files recorded with various SDRs, we hope that many DXers will use it. WavViewDX is compatible with multiple PC operating systems, including Windows, Linux, and macOS, and is freeware. According to Reinhard Weiß, additional features and enhancements are planned for the future, so we look forward to seeing its future developments. Finally, we would like to express our gratitude and respect to Reinhard Weiß for developing such useful and excellent software.

Reference Materials 

Table 1. Supported IQ Formats

ELAD FDM-SW2 Generic RAW recordings
GQRX recordings HDSDR
Jaguar Linrad RAW, single and dual-channel
recordings PERSEUS (*.wav)
PERSEUS P22 (*.P22) SDR#
SDR Console SDR Uno
SDRconnect SpectraVue
WiNRADiO DDC WiNRADiO RXW (only for G33)
Winrad

Trying WavViewDX on FM 

WavViewDX is primarily geared toward medium wave DX, but it seems like it can be used for FM DX as well. The image in Figure 4 shows reception from 79-87MHz using an RSPdx-R2 and an indoor YouTwin antenna. It supports stereo and has good audio quality. With an outdoor antenna, it could also be used for FM DX, such as with sporadic E and other short-lived propagation enhancements.

Figure 4

These English translations were prepared for IRCA’s DX Monitor, and are used with the kind permission of  IRCA as well as of the authors and the editor of the Totsuka DXers Circle publication, PROPAGATION.