DX Reminder Sources: Five DX Services Watched for You

An alert is only as good as the information behind it. When DX Reminder rings because your wanted callsign has appeared, the app has found that callsign in one of the public services that collect reports of stations on the air. The app does not rely on a single feed. The list of DX Reminder sources contains five of them, DXScape, DXSummit, DXHeat, PSK Reporter and Reverse Beacon, and understanding what each one brings explains why the alarm sometimes arrives within seconds and sometimes a few minutes after you saw the station on a friend’s screen. This article describes the five sources in plain terms, compares their speed and character, explains how the check interval and the alarm interval work together, and shows how to judge what you should expect from your own reminders.

Why Five Sources and Not One

No single service sees everything. A spot on a DX cluster exists because a human noticed a station and typed a report, or because a skimmer decoded a signal and published it. A reception report on PSK Reporter exists because a receiver somewhere decoded a digital signal. Each service has its own population of spotters and its own blind spots: a rare station on 17 metres FT8 may be reported at once by PSK Reporter and never appear on a cluster page, while a station working CW in a pileup is reported by humans and skimmers alike. By watching five services together the app widens the net, and the chance that a wanted callsign is missed falls accordingly.

The app description on the LY4A site puts it briefly: five sources at once, with band and mode kept apart, and CW meaning real CW only. The privacy page adds how the app talks to them: it asks the same public DX cluster services that a person would open in a browser, and each request carries the callsign being looked for. Those services see the request and the internet address it came from, and handle it under their own rules. Nothing else leaves the device on Android, Windows and Mac, and the apps contain no analytics, no crash reporting and no advertising.

The Five Sources One by One

DXScape, DXSummit and DXHeat are web services that present spots of DX stations, in a form that is easy to read and to query. Their data come from the cluster network, where operators and automatic skimmers report stations, and for a chaser they are the classical place to look: a line with the callsign, the frequency, the time, the spotter and often a comment such as “up 2” or “QSL via”. The article on DX cluster spotting and etiquette describes how these spots are made, and the guide to DXSpider commands and filters shows how the cluster itself can be filtered.

PSK Reporter is different in kind. It collects reception reports from stations running digital programs such as WSJT-X, and from many other receivers: every time a program decodes a callsign, it can tell the service where and when. For digital modes this makes it the nearest thing to a real-time map of who hears whom, as our article on PSK Reporter explains. The Reverse Beacon Network is the CW and RTTY counterpart. A network of automatic skimmer receivers decodes Morse and RTTY signals all over the world and reports every callsign they hear together with the signal-to-noise ratio. The article on CW Skimmer and the Reverse Beacon Network shows how it works.

Human Spots and Automatic Reports

The distinction between a human and an automatic source determines how you should read an alarm. A human spot usually means that someone has actually worked the station or at least heard it well, and the comment may contain the key information about where the station listens. It arrives with the delay of a person noticing and typing. An automatic report arrives as soon as a receiver decodes the signal, but says only that the signal was heard, with a signal-to-noise ratio, and it may come from a receiver in a place where your own propagation is nothing like it. For a rare station that is just starting up, the automatic report is the first sign of life. For the decision to start calling, the human comment is often more valuable.

A good way to use this knowledge is to watch for both. When the alarm shows a spotter that is a skimmer, take it as an early warning and look at the cluster to see whether a human has confirmed the station. When it shows a human spotter close to your location, you can be fairly confident that the signal reaches you.

Check Intervals and the Alarm Interval

Two settings shape how the sources are used. The check interval says how often the app asks the services, and the choices are 1, 5, 10 or 30 minutes. The app keeps running in the background and after a reboot, which is the reason why the check interval can be long without losing alarms: the app asks, and anything that is new since the last check is found. A shorter interval means a faster alarm, but also more requests to public services that are run by volunteers, so a reasonable person chooses the longest interval that still serves the purpose.

The alarm interval is different. It controls how often the same combination of callsign, band and mode may ring again. A single appearance on the air is reported by dozens of spotters, and the app gives one alarm for the newest of them. You can choose that the same station may ring again on every new spot, or only after 1, 5, 10, 30 or 60 minutes. The limit applies to that single callsign, band and mode: any other combination rings at once. For a pileup that lasts an hour, an interval of 30 or 60 minutes keeps the phone quiet while still giving you a fresh alarm if the station reappears later on another band.

Speed in Practice: What to Expect

With five sources and a check interval of five minutes, a typical delay between a first spot and your alarm consists of the delay of the source and the average wait for the next check, about two and a half minutes. If the first report comes from a human spotter, the human delay is added, which can be anything from a few seconds to several minutes. If it comes from PSK Reporter, the batch delay applies. The computer and phone versions listen to PSK Reporter reports over a live connection and hear a callsign within seconds of a receiver reporting it, which removes the batch delay for that source. The article on how to work a DXpedition explains how to use that early warning.

The status line of the app shows when the live feed is connected. If you prefer to save requests or work in a place with a poor connection, the live feed can be switched off under the sources in the settings, and the app falls back to ordinary queries. Newest spots are at the top of the list, so after an absence you see what appeared while you were away without scrolling.

Choosing Bands and Modes to Match the Sources

The table of bands and modes interacts with the sources in a useful way. A reminder for FT8 on 17 metres is matched against reports about FT8 on that band, which come mainly from PSK Reporter and from spots with that mode. A CW reminder looks for CW spots, which come from clusters and the Reverse Beacon. The mode cells are kept apart, and CW means real CW only, so a reminder for 20 metres CW does not fire for a digital signal on the same band. The more precisely you fill the table, the fewer unwanted alarms you receive. Details of the table are in the article on FT8 DXpedition mode and the set of cells that suits it.

If you chase a DXpedition that is operating on all bands, tick the combinations that you still need, and leave out those you have already worked. If you wait for a rare station on a band that is rarely open, such as 6 metres, a wide set of modes is a good idea, because you will take any contact you can make.

An Example Evening

Imagine that you are waiting for a DXpedition that has announced its start for the evening. You have ticked 20 metres and 17 metres for CW and FT8, with a check interval of five minutes and an alarm interval of 30 minutes. At 19:12 UTC a skimmer in Europe hears the callsign on 14.025 MHz in CW and reports it. The next check collects that report, and at 19:14 the phone rings with the callsign, band, mode and the spotter. You open the cluster page and find no human spot yet, so you know that you are early. At 19:20 a human spotter confirms the station with the comment “up 1”, and a second alarm does not follow, because the same combination may not ring again for 30 minutes.

At 19:50 the DXpedition moves to 17 metres FT8, and the PSK Reporter live feed hears it within seconds of the first decode. That is a different band and mode, so it rings immediately although the first combination is still within its interval. You now have an alarm for each combination as it appears, and a quiet phone in between. This is the behaviour the settings are meant to give, and it is why a careful choice of intervals is worth a few minutes of thought before the expedition begins.

The lesson of the example is to treat the alarm as the start of a short routine, not as the end of the task: confirm with a human spot or a second source, check the listening frequency in the comments, and then call. The alarm saves the waiting, and your judgement does the rest.

When a Source Is Quiet

Sometimes a service is slow or does not answer. Because the app uses five of them, one source going quiet does not stop the others, and the alarm still arrives from whichever service reports the station. The app does not hide the fact when a source falls back, and in the case of PSK Reporter the status line tells whether the live link is up. If you notice that alarms have become late, try the settings, check the internet connection, and see whether the other services show the same station on their web pages. A service that is down for maintenance is not a fault of the app.

The Bottom Line

DX Reminder watches five public services together: DXScape, DXSummit and DXHeat for DX spots, PSK Reporter for reception reports of digital modes and Reverse Beacon for CW and RTTY skimmer reports. Human spots add comments and confirmation, while automatic reports give the earliest sign that a station is on the air. The check interval of 1, 5, 10 or 30 minutes decides how often the services are asked, the alarm interval decides how often the same callsign, band and mode may ring again, and the table of bands and modes keeps the alarms relevant. The live PSK Reporter feed on the computer and phone brings those reports within seconds.

Frequently Asked Questions

Which sources does DX Reminder watch?

DXScape, DXSummit, DXHeat, PSK Reporter and Reverse Beacon, all at once, with band and mode kept apart.

Why are five sources better than one?

Each service sees a different part of the activity. Together they reduce the chance that a wanted station is on the air and never reported anywhere you are watching.

What does the Reverse Beacon add?

It reports CW and RTTY signals decoded by automatic skimmers, so it can show a station before any human has spotted it.

How often does the app check the services?

You can choose every 1, 5, 10 or 30 minutes. The app keeps checking in the background and after a reboot.

Why do I get only one alarm for a station that many people spot?

The app gives one alarm per callsign, band and mode, for the newest spot, and you choose how long to wait before the same combination may ring again.

Can I turn off the live PSK Reporter feed?

Yes. It can be switched off under the sources in the settings, and the app then uses ordinary queries instead.