Tag Archives: Software Defined Radio

Part Three: A Beginner’s Guide to ALE

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

A Beginner’s Guide to ALE: Part Three

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 the first two parts [Part 1 and Part 2] we looked at software used to decode ALE signals. Now let’s look at the stations and countries waiting to be logged.

If you’ve read the first two parts of this series then you know that there is no listening involved in ALE DXing. I know some traditionalists who would claim it’s not real DXing if you aren’t sitting next to the radio listening to a speaker or headphones. To me, DXing is having fun by logging new and interesting stuff. With ALE, the fun comes from researching the callsigns and frequencies to figure out what was logged. Every DX session produces numerous puzzles.

Identifying ALE stations may not sound hard. After all, one of the best things about monitoring ALE is that the stations are constantly identifying themselves. What could be easier? Unfortunately, it’s not always that easy to match up the callsign with what organization is behind it. Obvious location identifiers like ILLAPEL and VILLAVICENCIO2 are the exception, not the rule.

Around a third of the callsigns I decode stay complete mysteries as to who is behind them and where they are from. For about another third, the organization may be known (and, by extension, the country), but not the transmitter site. Only about a third of my ALE catches can be pinpointed exactly on a map as to where they came from. I wish it were more than that, but that doesn’t mean I haven’t logged some really interesting and unusual places.

Actually, it is surprising that I can pinpoint as many as I do. After all, every ALE network I’m aware of belongs to a government agency, a military, or some other government-affiliated organization. Bureaucracies like those are typically very careful about how they share information even when there is absolutely no security risk involved. Nevertheless, the utility DX community has gathered some excellent information over the years. While some of it is researched from public sources, I understand that some of it comes from inside sources that certain DXers have with people who install the networks. I don’t ask questions about where the information comes from and I’m glad to have the references and lists, which you can find in the links below.

Join the UDXF

The best source of ALE information is the Utility DXers Forum. The UDXF website has a lot of great utility resources that anyone can download. The best information, however, is the members’ loggings. To see those, you have to join the mailing list, where you can see member logs reported in the daily messages. But what you want to do is download the log compilations from the Files section (at Groups.io). Those go all the way back to the UDXF’s founding twenty years ago.

The first zip file is a compilation of all the logs from 2006 to 2019. After that, the logs are compiled into files for each year from 2020 to 2025. Download all of these and unzip them into a single folder. And periodically check back for newer files. At the beginning of each month, there will be a compilation for the previous month. Those will be compiled into a single file for 2026 at the beginning of next year. Finally, you need a way to search within the contents of an entire folder of files. A good text editor, such as Notepad++ for Windows, will do the job.

So let’s say I have a logging with the ID of 355013 on 8092 kHz. That really doesn’t tell me a thing about who could be behind the signal. Lots of organizations use six-digit strings as identifiers. I open up the Find in Files feature in Notepad++ and point it at the folder of UDXF logs. Now I type in the ID followed by a colon. Why a colon? Because in the UDXF logs, IDs are followed by a colon. By including the colon in my search term, I can eliminate any other random places that the same string of characters might be. (That’s more important when searching for shorter ID strings, such as three-digit numbers.)

I click Find All and get back a listing of every line in those logs that contains my search string. I can click on any line to open that file at that point. In the frequency column here, I see two hits for this ID on 8092 kHz. I think I can be certain that this is the Turkish Civil Defense station in Samsun province.

But what if I got these same results, but without any reports on 8092 kHz? That wouldn’t prove that I had logged Samsun even though the six-digit ID is a match on other frequencies. There are other organizations that also use six-digit numbers as IDs, such as UN Peacekeepers in several African countries. What I would do then is run a search for the frequency of 08092 (no colon) to see what other stations have been reported there. That turns out to be an important frequency in the AFAD network, so I could still safely assume that I had logged Samsun.

If the identifier doesn’t show up in the UDXF logs then there are some other resources (listed below) that can be checked. Sometimes the UDXF has complete network lists that include stations not yet reported in the logs. Another thing to do is look to see just what has been reported on that frequency. If there are lots of logs from a particular organization and the IDs follow the same pattern as the one you logged (e.g., six digits beginning with a ‘3’), then you likely got an unknown station in the same network.

If I get this far and still have no idea who is behind the station, then I have two options. I can delete the log and forget about it. Or I can put it in a ‘check later’ list, which I go through every year or so. I’ve identified a number of stations that way, especially from new networks. To be honest, which one I choose to do depends on how I feel that day!

Now let’s take a look at some of the places that stations can be logged from.

North America

The US government heavily uses ALE and there is no question that you will log more stations from the USA than from any other country.

The most widely used set of frequencies by the US government includes 7527, 8912, 10242, 11494, 12222, and 15867 kHz. These frequencies are shared by several organizations, including the US Coast Guard, the FBI, the DEA (Drug Enforcement Agency), and the Customs and Border Patrol. The USCG is an especially heavy user, and it’s easy to log not only USCG bases but also USCG cutters at sea, as well as USCG aircraft. Another heavy user of these frequencies is the COTHEN network, or Cellular Over-The-Horizon Enforcement Network.  This is a network of various law enforcement agencies and includes stations in some unusual places such as Limestone, Florida, and Lovelock, Nevada. Here is a string of Black Cat loggings on five different frequencies by MEM, the COTHEN station in Senatobia, Mississippi.

Another large US government ALE network is run by FEMA (Federal Emergency Management Agency), which operates stations at each of its ten regional offices. The callsigns include the region number, e.g. FC4FEM1 from the region four office in Thomasville, Georgia. If you are in North America, it won’t take long to log all ten regions. Much rarer are the stations in individual state offices, such as SD8FEM in South Dakota and TN4FEM in Tennessee.

Some state National Guard units also operate on ALE, but by far the most active are the Wyoming and Utah National Guards. These can be logged on several frequencies, including 7805, 7932, and 8065. The Wyoming stations mostly identify by the full town name, e.g. LARAMIE or GILLETTE, while the Utah stations use the first three letters of the local base, e.g. AME for American Fork or TOO for Toole. In September, I passed through Vernal, Utah, and took these pictures of the Vernal National Guard center and the HF antennas on the roof.

Finally, there are several regional government and quasi-government organizations that can be logged. The most active network is probably the Bonneville Power Administration in the Pacific Northwest. It operates a handful of stations with calls including 1121BPA and 1351BPA. Unfortunately, there is no information as to where the individual stations are located.

US government ALE transmissions are not confined to the continental USA. As noted in part one of this series, the US Air Force operates from bases around the world. The US Coast Guard operates from Puerto Rico, Guam, Alaska, and Hawaii. The DEA has a station in Nassau, Bahamas. Finally, the US State Department operates from many consulates and embassies around the world.

The Canadian military has a few ALE stations on the air. Aside from that, to my knowledge, there is no ALE activity from Canada, Mexico, or any of the countries in Central America and the Caribbean, except for that done by the US government.

South America

The militaries of Brazil, Colombia, and Venezuela all operate ALE networks. The Brazilians seem to be particularly active. The police networks of Chile and Colombia, as mentioned in part one, are the most interesting as they identify with the station location. However, logging the Chileans in the northern hemisphere will require good conditions. I’ve only managed to get a few when DXing in the USA, although I have logged several more while DXing in South America.

Africa

Algeria is the heaviest user of ALE from Africa. The Algerian Air Force and Army operate from bases throughout this huge country, and in many cases, the exact locations of the stations are known. One of my favorite ALE logs is CM6 from Tamanrasset in the heart of the Sahara in southern Algeria. Sonatrach, the Algerian national oil company, also has a huge network of stations using four-digit numbers as identifiers. Unfortunately, there is no information as to the exact location of any of those stations.

Morocco, Mauritania, and Tunisia are three other countries with large ALE networks operated by their militaries and/or national police. Finally, United Nations Peacekeepers operate from several countries, including Mali, the Central African Republic, and South Sudan.

Europe and the Middle East

The United States may have the most ALE stations, but without a doubt, the most active ALE callsign is XSS from Forest Moor, England. Operated by the British military, this station pops up on dozens of frequencies throughout the shortwave spectrum. The previously mentioned Turkish AFAD operates what is probably the largest ALE network in this region. Another large network is Italy’s Guardia di Finanza, a sort of combination coast guard and tax enforcement agency. It’s hard to receive in North America, but I did once get one of their patrol boats. ALE is used by the militaries and border patrols of several other countries in this region. My best ALE catch from Europe is getting the Polish UN Peacekeepers in Kosovo. That’s my only logging of any type in that small country.

Asia and Pacific

Australian state police run an ALE network with 10505 kHz being a favorite frequency. To my knowledge, there is no other significant ALE activity in the region aside from that of various US government organizations.

That’s just a general overview of the major users of ALE, but there is a lot more to be logged that I didn’t mention. Unlike a lot of things on HF, the use of ALE is expanding, not contracting. For example, the Colombian police network didn’t even exist two years ago. So, give ALE monitoring a shot. I think you’ll find it to be one more way to make the DX hobby challenging and fun. I do.

Links

Part Two: A Beginner’s Guide to ALE

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

A Beginner’s Guide to ALE: 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 the first part of this series, I explained what the digital ALE mode is and looked at an easy way to get started monitoring ALE stations. In part three, I’ll look in detail at the dozens of countries and hundreds of stations that can be logged in ALE mode. But first, let’s look at a way to let software do the hard work in adding those hundreds of stations.

The Black Cat Approach

Run by longtime DXer Chris Smolinski, Black Cat Systems is a provider of over two dozen quality software programs for radio hobbyists. The one we’re interested in is the Black Cat ALE Vacuum Cleaner. The name describes exactly what it does. The user feeds it a large number of SDR spectrum recordings, and the Vacuum Cleaner sucks up the ALE DX and lists them in a file.

Let’s step through the basics of using the program. But first, you need at least an hour or two of SDR spectrum recordings covering frequencies with lots of ALE traffic. Some of my favorite ranges are 7500-9200 kHz, 10100-11500 kHz, and 15500-16500 kHz.

Here’s the main screen on the Vacuum Cleaner:

I recommend you check both USB and LSB. In the logs reported to the Utility DXers Forum, about 97% of all ALE transmissions are in USB mode. From my experience, if LSB is unchecked, the Vacuum Cleaner will step through the files about twenty percent faster, but you will miss a tiny number of stations.

The kHz settings determine how finely the application will tune in looking for ALE signals. I recommend just checking x.0kHz and x.5kHz. Almost all ALE signals on shortwave are transmitted on frequencies that end in either point-zero or point-five kilohertz. The main exception is the US Department of State, which uses frequencies ending in point-six kilohertz (e.g., 8058.6 kHz). Fortunately, the one-hundred Hertz difference from the point-five kilohertz setting isn’t enough to make a difference except maybe with the weakest of signals.

The next step is the Settings, which are found under the Edit menu. Most values can be left at the defaults.

At the top, the number of decoding threads should be no more than the number of cores that your CPU has. Check the Auto Log box, then enter a destination path to record logs to a file. (Otherwise, the logs that show up in the window will be gone when you close the program.) Next, select the file format of the SDR program used in making the I/Q recordings. Finally, set the file format for your logs. I prefer the single tab format so that I can later import the logs into Excel and sort by frequency.

Now it’s time to decode. Under the File menu, select Open I/Q Files and browse to a folder of spectrum recordings to decode. Click on Open in the file selection box, and the Vacuum Cleaner will start decoding the files. Now take a break and come back in fifteen or twenty minutes. The main screen should look like this.

The current settings and the frequencies being scanned are displayed at the top, under the settings checkboxes. There are actually only 1232 distinct frequencies in that range, but the number is doubled as each one is being checked in both LSB and USB. Below that, the output window lists each file as it is being scanned and ALE logs as they are found. (But be sure you are also recording these to a text file.)

To see a list of files still in the queue, select File > Show I/Q Files Awaiting Processing. After a few files have been processed, this will also show an estimate of how much time is needed to complete the queue. To add additional files to the queue, select File > Pause Processing, add the files, and then select File > Resume Processing. Note that the Vacuum Cleaner processes files in date/time order. If you add files that were recorded earlier, they will go to the front of the queue.

How Long Does This Take?

In the above image, notice that after each file is finished, the time taken to decode it is displayed. These files were all exactly 326 seconds long, and the first one took 262 seconds to decode for a speed of 1.24x actual time. That may not seem important, but it depends on how much you have to decode. In a couple of days of serious DXing with my three Airspy receivers, I can easily accumulate a couple of terabytes of spectrum recordings.

Processing time depends on several factors. The first is the bandwidth/sampling rate. Those files above were recorded with SDR-Console at 768 kHz wide. All other things being equal, a narrower sample will process faster and a larger one more slowly. Depending on the band being monitored, I sometimes record with my Airspys at the 912 kHz bandwidth. Those typically take about 25% longer to decode than 768 kHz files.

Another factor is whether or not the Vacuum Cleaner has to share processing power with other running applications. That slows things down. I mostly decode overnight or at times when I’m not otherwise using the laptop. Under those conditions, my 768 kHz files decode at 1.75x and my 912 kHz ones at 1.45x. But those numbers are for my nearly four-year-old main laptop. An older laptop I have at home tops out at around 1.40x on 768 kHz files with nothing else running. If you have a high-performance gaming laptop, you should get much better numbers than I.

Then there are differences between the various SDR applications in how they store data. I won’t go into the technical details that Chris explained to me, but SDR-Console is more efficient in this regard. In my own testing, I found that files of similar bandwidth and time length recorded with SDR-Console decode at least fifty percent faster than those recorded with the default Elad and Perseus software. I’m satisfied with SDR-Console, so I haven’t tried any other programs. If you have other favorite SDR applications, I suggest doing some comparison tests to see what works best for you.

One application that you shouldn’t use is HDSDR. Chris didn’t have good documentation on the file format for this one and wasn’t fully successful in reverse-engineering it. The Vacuum Cleaner will work with HDSDR, but almost all the callsigns that it finds will be errors. And that brings us to an important question.

How Accurate Is It?

When I started using the Vacuum Cleaner, my main concern was whether it would miss valid signals. There was only one way to find out, so I ran several tests. I would give the Vacuum Cleaner a few hours of I/Q recordings to decode, and then I would process the same recordings manually using Sorcerer, as described in part one. Black Cat not only correctly identified every single ALE transmission that I found with my eyes but went way beyond that. It also found and decoded weak and noise-covered signals that I couldn’t see in the Data Analyzer window but were there when I played them back.

As Chris points out in his documentation, the emphasis on weak signal detection does cause the application to sometimes falsely report bogus callsigns. Some of these are produced by random noise, fooling the system. Others come from poorly received signals. He could have taken a ‘high confidence’ approach and only presented callsigns that had been clearly received. But that would have meant some valid callsigns not being reported. Instead, he went with displaying everything. It’s up to the user to weed those out.

If the decode doesn’t contain any of the keywords (TO, TIS, and TWAS) then it’s probably an error. But poorly received signals can cause partial and incorrect callsigns to be reported with a keyword. Spotting those just takes the knowledge and practice that comes from using the program and ALE reference materials. (That’s the topic of part three.)

Is It Worth the Price?

Black Cat ALE Vacuum Cleaner is a high-quality software available for Windows and macOS, and you can try it before buying. The cost is $99.99.

Is it worth it? If all you want to do is sample what ALE is all about, then probably not. But if you get serious about ALE monitoring and want to add hundreds of ALE stations to your logbook, this is the way to do it. I am 100% satisfied with the Black Cat ALE Vacuum Cleaner. I’ve decoded several thousand hours of I/Q files with it over the past few years. (When running multiple SDRs at a DXpedition, it’s easy to accumulate seventy or eighty hours per day.) The program also has a few other tricks I haven’t covered. For example, it is possible to actively monitor a folder and decode I/Q recordings as they are created.

In part three of this series, I’m going to take an in-depth look at the countries and stations that can be logged in ALE mode. Once you’ve seen how much DX there is to log, you might just be convinced, like me, that the program is worth the price. And you married guys can tell the wife that you’re buying a new vacuum cleaner that only you will use, hi!

The Vacuum Cleaner isn’t the only program that Chris has for ALE monitoring. Black Cat ALE is a different program that does live monitoring of up to twenty-four ALE frequencies simultaneously with SDR-Console, assuming your laptop has the resources to handle that.

Finally, Chris tells me that he’s been experimenting with using the Vacuum Cleaner with wide-bandwidth I/Q recordings on high-end laptops. On his M4 Max MacBook Pro, he’s able to process 32-MHz wide recordings at about 0.50X real time and 16-MHz wide recordings at about 0.97X real time. As he says, it won’t be long until it will be possible with the right equipment to monitor the entire HF spectrum for ALE signals in real time. And that will be fun!

Links

Part One: A Beginner’s Guide to ALE

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

A Beginner’s Guide to ALE: 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.

To me, part of the excitement of DXing has always been logging new stations. From the very beginning (over fifty years ago), I went after shortwave broadcast (SWBC), medium wave, and voice utility DX. Up until the mid-90s, I usually averaged logging one new SWBC station per week. Today, it’s hard to add more than one or two each year. There are also far fewer voice utility stations on the air today. At least medium wave is still going strong. Several years ago, my quest for logging new stations on the shortwave frequencies got me involved in DXing digital utility stations. I wrote an article here on monitoring DSC stations: https://swling.com/blog/2022/11/guest-post-monitoring-digital-selective-calling-dcs-with-yadd/).

But DSC is just one of several digital modes that I’ve been playing around with. The one that I’ve found most interesting – and the one that has yielded hundreds of new stations in numerous countries – is ALE.

Now, I am not an expert at monitoring ALE. I’m just an advanced beginner. But I think I know enough to help other beginners get started. And if you are an ALE expert reading this, I welcome your additions, corrections, and even criticisms to the comments section. I still have a lot to learn, too.

What is ALE?

Ever since the early days of radio, one of the most important uses of the shortwave spectrum has been two-way communication. It provides a means for an organization’s far-flung offices or bases to communicate without relying on external infrastructure. That remains true even today because satellites can malfunction and evil powers can cut undersea cables.

But shortwave isn’t consistent. The frequencies that work best between any two points will vary by time of day, time of year, solar conditions, and a host of other factors. In the old days, radio operators had to understand radio propagation to make an educated guess as to the best frequency to use to reach a particular distant station. Sometimes they guessed wrong, and stations would struggle to communicate or maybe not even connect. ALE, or Automatic Link Establishment, was designed to make two-way shortwave communication as simple as making a telephone call. Depending on your point of view, it has taken the guesswork out of frequency selection … or made it so easy that any dummy can be a radio operator.

In an ALE system, each station is assigned a unique identifier and the network has a set of preconfigured frequencies spaced throughout the shortwave spectrum. For example, here’s a partial list of frequencies and stations for the United States Air Force, one of the most active ALE networks.

USAF Common Frequencies: 4721, 5684, 5702, 6715, 6721, 8968, 9025, 11181, 11226, 13215, 15043, 17976, 18003, 23337, 27870 kHz

Most Active USAF Stations

  • ADW Andrews Air Force Base, Maryland, USA
  • AED Elmendorf Air Force Base, Alaska
  • CRO Croughton Air Base, United Kingdom
  • GUA US Air Force Base, Guam
  • HAW Hawthorn Air Force Base, Ascencion Island
  • HIK Hickman Air Force Base, Hawaii
  • ICZ US Air Force Base, Sigonella, Sicily, Italy
  • JDG US Air Force Base, Diego Garcia Island
  • JNR US Air Force Base, Salinas, Puerto Rico
  • JTY US Air Force Base, Tokyo, Japan
  • MCC Beale Air Force Base, California, USA
  • OFF Offutt Air Force Base, Nebraska, USA
  • PLA Lajes Field, Azores

The key to the system is a piece of software called the ALE controller. At periodic intervals, the ALE controller at a particular station, say PLA, will loop through the frequencies and send a “sounding” out on each one. That’s just a short digital identification burst saying “This is PLA!” Here’s a recording of an ALE sounding.

That’s not the kind of signal that anyone would enjoy listening to all day. Fortunately, no human being has to do that. Instead, all the other controllers in the network are monitoring every frequency and automatically make note of how well PLA is received (or not) on each channel. Now, if someone at Offutt Air Force Base needs to send a message to Lajes, they just go to their ALE controller and enter “PLA.” The system will select the best frequency to use based on the most recent observations. That’s the basic explanation. If you want to understand more, see the links at the bottom.

Monitoring ALE

You can’t DX ALE with your ears. A computer program has to do it for you. There are several hobby programs that do the job, and I’m going to look at two of them. The first one will get you started, and the second one will take your ALE DXing to the top.

I began with Sorcerer, a free program that decodes several dozen digital modes. See the links below for downloading. The program doesn’t need to be installed. Just unzip the file and place the executable in a suitable location. Next, you need an SDR and an SDR application. I prefer SDR-Console for digital work, but any SDR program will work if you can feed the audio into a virtual audio cable. And that’s the other thing you need – a direct audio connection from the audio output of your SDR application to Sorcerer. There are several similar products available, but I recommend VB-Cable. Your first VB-Cable is free, and you only need one to run Sorcerer. If you want to expand, you can buy more VB-Cables later.

Here’s the main window that opens when you start Sorcerer.

The first time you use Sorcerer you will need to connect it to your VB-Cable. On the menu select File then Options. Find the cable under the Soundcard list and save.

Open your SDR application and tune it to 11181 kHz. Set to USB mode with a filter value of around 2.8 kHz. That is one of the most heavily used frequencies by US Air Force bases around the world. Wherever you are, something should be received. Next, set the audio output of your SDR application to go to VB-Cable. In SDR-Console that’s done by a drop-down box under the current frequency. Next, slide the volume level all the way up.

Now go back to Sorcerer and confirm you are getting audio from the SDR application.

Now select Add Decoder from the top menu in Sorcerer. Then select SELCALL on the left side and scroll down and double-click to select MID-STD 188-141A ALE from the options.

That will open a large decoder window, which you can resize as needed.

Now, go get a cup of coffee and come back in about thirty minutes.

Sample Sorcerer Output

Let’s take a look at some sample output from Sorcerer. These loggings were made on 7915 kHz, a frequency used by the Carabineros (National Police) in Chile. First, Sorcerer shows the time and date the decoding was done per the current time on the laptop. If you are monitoring live, those are the correct date and time of the reception.  For the record, I was decoding from SDR spectrum recordings in these examples, so the times and dates are not the real ones. (I got the real ones from the spectrum recordings.) TWS stands for “This Was” and EOM for “End Of Message.” ILLAPEL and TALTAL are the station identifications, which in this case correspond to two Chilean cities. Note that sometimes the end of the ID can be cut off if reception isn’t clear.

These next loggings are from the national police of Colombia on 7560 kHz. Villavicencio is a city east of the Andes, and Sumapaz is a national park in the remote mountains south of Bogotá.

Here is a string of loggings on 7527 kHz, a frequency used by the US Coast Guard and other US government agencies. But here we have a TO, which means someone is trying to call X09. That happens to be a C-27J Spartan, a medium-range surveillance aircraft used by the US Coast Guard. Who’s doing the calling shows up in the final line. TIS (“This Is”) is a variation on TWS. LNT is the identification for CAMSLANT, the big US Coast Guard station in Portsmouth, Virginia.

The Limits of Single Frequency Monitoring

DXing live and monitoring one highly active frequency at a time with Sorcerer makes for a good introduction to ALE. However, if you just stick to monitoring easy frequencies like the USAF ones, you’ll get a lot of logs, but it won’t take long until you feel as if you’ve gotten everything. There are hundreds more ALE frequencies out there, such as the Chilean and Colombian police ones. But those are less active and might only be received at your location when conditions are just right. If you go after those by live monitoring with your SDR parked on a single frequency, you’ll spend a lot of days without getting a single hit.

What is needed is a way to cast a wide net to catch all the activity in a particular band. The idea I came up with was to use the Spectrum Analyzer feature of the SDR-Console program. See my article on this highly useful feature for an understanding of how this works.

Using an Airspy HF+ Discovery, I would make several hours of spectrum recordings and then use the Spectrum Analyzer to visually find the ALE signals. Here’s a string of three long ALE bursts on 7953 kHz and a single weaker one on 7991 kHz. (Some other digital modes look the same on screen.)

I just had to click on a signal to play it into Sorcerer to get the ID. The process worked really well, and I found a lot of stations this way. But it was also tedious and time-consuming. I wanted something better … something that did the hard work for me. That’s what technology is for, right?

Stay tuned for Part Two … 

Links

Meeting WavViewDX Developer Reinhard Weiß, and Visiting Akihabara With Him (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). Here, Kazu Gosui recounts his meeting with WavViewDX developer Reinhard Weiß during his visit to Tokyo .

Meeting WavViewDX developer Reinhard Weiß, and Visting Akihabara With Him

by Kazu Gosui

I first learned about WavViewDX in January of this year on the mailing list of the American radio club IRCA. It was described as “analysis software compatible with I/Q WAV recordings created with almost all SDR software,” so I was intrigued. I quickly downloaded it and tried it out, and I was immediately impressed.

In early February, I emailed the developer, asking, “I’m amazed at how easy it is to use and how powerful it is. It works fine with PERSEUS and AirSpy HF+, but are there any plans to support WiNRADiO’s DDC format?” Reinhard Weiß (hereafter referred to as Reinhard) responded that same day, “I’m actually currently working on adding support for WiNRADiO’s G33DDC. I should be able to send you a test version tomorrow.” The email carefully explained the import procedure and important points to note.

The text, the web page description, and the tone of the expression conveyed a sincere and attentive personality. The next day, I tried out the sample version and reported some concerns. Reinhard quickly fixed them, and where he couldn’t immediately fix them, he supported me by sending files via the cloud or screen capture videos. As I continued to request things like adding a shortcut for switching receive modes, I gradually became fascinated with WavViewDX and, before I knew it, became a heavy user.

The first email also asked, “I’m planning to visit Japan in May or June. Are there any ham or BCL (Broadcast Listener; SWL) events in Japan around that time?” In response, I suggested that if Reinhard could come to Tokyo, we could hold an offline meeting with members of TDXC! Through our exchange, I realized that Reinhard is quite knowledgeable about Japanese affairs. He knows Akihabara very well, and even knows Hard Off as a good place to get BCL radios. He loves hot springs and enjoys talking about Japanese food. When I asked him, “Is your wife Japanese by any chance?” he replied, “Yes.” No wonder he’s so knowledgeable! He should have told me sooner! (lol) So, we made an appointment for an offline meeting in Akihabara, Tokyo, in late May.

On the day, we met at the Electric Town exit of JR Akihabara Station. Our four attendees were Hiroo Nakagawa, Satoshi Miyauchi, Fumiaki Minematsu and myself. When I arrived at the meeting point five minutes early, they were already there. When I asked him, “Excuse me, Reinhard-san?” he replied, “Yes, that’s right,” in Japanese. His Japanese was fluent! Up until now, emails had been in English, as I don’t speak German, so I had no choice but to communicate in English… I was completely surprised because I had been counting on the others and Google Translate on my smartphone to converse in English! You should have told me sooner, Reinhard! (lol) Needless to say, from then on, the entire conversation was in Japanese. The meeting venue was a pub near the station. He could read the Japanese menu, and thanks to his wife, who is apparently a good cook, Japanese food was also OK, so no problem.

We spoke about radio and BCL. Reinhard started medium wave DX about three years ago.  He has been interested in radio since he was a child and actually worked as a BCL radio broadcaster. He has had a long career. His job is developing debuggers for testing and verifying the operation of in-vehicle electronic devices and measuring instruments. He says that both his work and his hobby are focused on developing easy-to-use hardware and software integration. He developed WavViewDX while studying the programming language Python, and runs it at home using two PERSEUS devices.

He said he would be happy if many people use it. Currently, WavViewDX has 200 users, 25 of whom are active worldwide. Incidentally, the mailing list has 102 subscribers (as of June 10, 2025).

Over lunch, we had the opportunity to use WavViewDX on the PC we brought with us, and it was extremely valuable to have the developer himself explain how to use it, provide an overview of its functions, and explain the development concept.  We also received copies of the German BCL magazine “Radio-Kurier” (a radio delivery service?). This magazine apparently publishes an astounding 2,000 copies per month, demonstrating the depth of Germany’s BCL population. The most active BCLs are few, and 80% of the articles are written by one person. That’s impressive.

The second half of the meeting was a tour of Akihabara’s famous shops. We visited the Radio Center rental showcase, Uchida Radio, Radio Department Store, Rocket, Fuji Musen, and Akizuki Denshi. Reinhard has a keen interest in vintage Japanese BCL radios and boomboxes, and his eyes lit up as he looked at rare radios and boomboxes. At Uchida Radio, he even negotiated the price of a radio cassette player he was interested in.    Unfortunately, the deal fell through, but he apparently toured Hard Off stores around Tokyo the next day, so he must be a die-hard enthusiast. He also seemed to love the Fuji Wireless and Akizuki Electronics stores on the second floor, saying, “Their unique products are what keeps them going, and I can see why they’ve survived.” He bought a large breadboard (brand new!) for 50 yen on the second floor of Akizuki and then we took a break for tea in the cafe.

We had a great time chatting there, too. Reinhard is, in a word, a nice guy. A German who speaks Japanese, loves radio and BCL, and develops software for BCL—an extremely rare and valuable person. He’s fluent enough in Japanese to even tell jokes, and he’d laugh along with us at our old-man jokes. He was friendly and fun to talk to, and we shared the same values as fellow enthusiasts. It felt like we were old friends.

He apparently returns to Japan every year with his wife, but he hasn’t done a DX expedition yet. Maybe the next one will be the Chigasaki expedition?! So we parted ways, hoping to see each other again next year.

(l-r: Kazu Gosui, Satoshi Miyauchi, Hiroo Nakagawa, Reinhard Weiß, Fumiaki Minematsu) —Hiroo Nakagawa photo

(l-r: Kazu Gosui, Hiroo Nakagawa, Reinhard Weiß, Satoshi Miyauchi) —Fumiaki Minematsu photo

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.

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.

Unlocking Rare DX Treasures with SDR-Console’s Powerful Data File Analyzer Tool

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Finding Rare DX with the Data File Analyzer

By Don Moore

Don’s DX traveling stories can be found in his book Tales of a Vagabond DXer. 

I’ve been a real jack-of-all-trades in my over five decades of DXing. I began with SWBC (shortwave broadcast) but soon branched out to medium wave and voice utility. Later I added longwave beacons and more recently I’ve gotten into digital utility stations. My goal has always been to log lots of different stations from lots of different places. And the rarer they are, the better.

For SWBC and medium wave stations, as well as scheduled utility broadcasts such as marine and aeronautical weather reports, the DXing process is simple. You tune to a frequency at a time when a station is scheduled to be on the air. It’s either there or it’s not there. If it’s not there then maybe propagation isn’t right or maybe your antenna/receiver setup isn’t the best for that frequency band or the station’s power level. You tune away to find something else with plans to try again another day.

But it’s not always that easy. Most utility stations do not have fixed schedules and only come on as needed. The best example of that is two-way marine, aeronautical, and military voice communications.

In eastern North America, tune to 8906 kHz anytime from late afternoon until morning and set your receiver to USB mode. You’ll probably hear empty static at first but it’s unlikely that more than ten or fifteen minutes will pass before you’ve heard some aeronautical traffic. The frequency is assigned for communication on the North Atlantic and is heavily used by aircraft communicating with New York Radio, Gander Radio (Newfoundland, Canada), and Shanwick Radio (Shannon, Ireland). If you keep listening, the frequency will probably be occupied around 25% of the time. Wherever you are in the world, there are a few heavily used air frequencies like 8906 kHz and listening to them can be fascinating. But I want to log more than just a few easily heard stations.

Sticking to aeronautical DX, there are many assigned frequencies for different regions and air routes around the world. But propagation to those distant areas is unpredictable and less-used routes have fewer flights. Fewer flights mean less radio communication and more empty static. The most interesting frequencies may only see traffic a few times a week.

Hearing the rarest voice utility DX requires listening to lots of empty static just to get a brief DX catch. For years my process was simple. I would set my receiver to an interesting frequency and leave the tape recorder running while I sat nearby listening and doing something productive. I got some very good DX over the years that way. But I don’t want to think about how many long hours of empty static I listened to in order to get that DX.

 

SDRs offered some improvement. Instead of audibly monitoring a specific frequency I could now make a spectrum recording that included a band of interest, say the 8815 to 9040 aeronautical band. During playback I could visually monitor the SDR waterfall for interesting signals. That works. But watching an SDR waterfall scroll by for three or four hours gets tedious quickly.

(When I refer to SDRs, I mean ones consisting of a small box that is connected to and controlled from a computer using a software program. None of this applies to models such as the Malachite line or the Icom IC-R8600, which use SDR technology inside but mostly function as a traditional receiver.)

Finding a Better Way

That better way is, I think, one of the most exciting DX tools out there – the Data File Analyzer in the SDR-Console program. Since I learned about it a few years ago, the Analyzer has gotten me all kinds of catches that I probably wouldn’t have gotten otherwise. Let’s start with an overview and then dig into the how-to.

SDR-Console is one of the better-known SDR programs and it works well with most of the common SDR radios on the market, including the Airspy, Elad, Perseus, and SDR-Play models. Here’s what the main window looks like:

The Data File Analyzer is a second window that produces a scrollable waterfall display for the entire length of an SDR spectrum recording. The display is similar to a standard waterfall with frequencies along the bottom and times along the side. However, there is also a scroll bar on the right side for browsing through the entire length of the recording. Instead of watching a four-hour spectrum recording slowly roll by in real time, I can scroll through the window looking for DX.

And this is what makes the Data Analyzer really useful. When I spot an interesting signal, I click on it and that causes the main window to start playing at that time and frequency. Now going through a four-hour spectrum recording takes from a few minutes to around half an hour, depending on how much DX I find.

Here’s a closeup of part of that same screen of spectrum recording made on 24 October 2024 at a DXpedition in western Pennsylvania, USA.

“A” marks a short exchange between an aircraft and Ndjamena Radio in Chad on 8894 kHz. “B” is Niamey Radio in Niger on 8903 kHz. “C” is Gander Radio on 8891 kHz. Just to the left of that is a string of digital signals. “D” is New York Radio on 8918 kHz. Again, there is a string of digital signals just to the left. Finally, “E” is communication from Dakar Radio in Senegal and Sal Radio in the Cape Verde Islands on 8861 kHz. I caught four African aero stations in just four-and-a-half minutes. I could also show you long stretches of time when there was nothing interesting coming in. With the Data File Analyzer I was able to visually find and focus on the DX and not waste my time with the empty static.

Here’s another image taken at the same DXpedition. Notice the three transmissions between 8820 to 8845 that seem to be mirroring one other.

That turned out to be Flightwatch Brisbane, the Australian regional aeronautical network. It uses multiple transmitter sites on 8822, 8831, and 8843 kHz to cover the entire country. I had never logged it before and I doubt I would have found it if DXing in the traditional manner.

The How-To

Here I’m going to assume that you already have SDR-Console installed and know the basics of how to use it, including making spectrum recordings. (If not, see the links at the end.) This article was written using version 3.4 of SDR-Console. Some of the functionalities described are not in earlier versions, so upgrade if you are not up to date. And I should point out that while you can do this on a single monitor, it works more smoothly if you have a dual monitor setup and can put each window on a different screen. Continue reading →