Tag Archives: Digital Modes

DigiFAQ Updated: An HF Digital Decoding primer and reference tool

Many thanks to SWLing Post contributor, Mike Agner, who writes:

[S]ome 20 years ago, Mike Chace-Ortiz, Stan Skalsky, myself and a bunch of other folks put together a FAQ about digital modes on radio – specifically modes going from LW way up into the UHF spectrum- called the DigiFAQ 5.3. I was responsible for the HF Software section, and as you might know, back then it was all about the hardware. InfoTech was still around, and amateur digital modes using the PK232 were plentiful. There is a PDF-based copy on the UDXF website [click here to download].

Now jump ahead 20 years or so, and things have changed considerably. Hardware is no longer king, and soundcard-driven software has taken over the market. Even receivers have changed – the desktops of old (quite apart from the current batch of ham transceivers that have general coverage radios built in) have been pretty much supplanted by Software Defined Radios. Along with that, the digital modes themselves have changed drastically with some disappearing altogether, with new ones like ALE going to the head of the pack. Too, the original DigiFAQ combined many ham-related modes along with everything else.

[O]ur original work didn’t really address some of the basic questions newcomers to this side of the hobby might have, [s]o with Mike Chace-Ortiz’s help, I have been involved in rewriting and updating the FAQ. Its approach is different – we start from topics like discussing radios, SDRs, some of the terminology you will see on mailing lists like the UDXF and much more. Only after we cover all of this do we discuss decoders – and even here, this topic is broken down even further, to include those decoders that play nice with some SDRs, and some of the tools you can use to help analyze an unknown signal.

Then we go into the modes (most are HF related, but we do touch on one or two common LW modes). We identify those modes that are dead, and separate them from the rarely used/active ones. Where possible we also supply waterfalls for each.

We also have an extensive appendix with a whole bunch of links for additional reading.

Perhaps of greatest use to newcomers is a listing of known scheduled broadcasts, so they can test what they download without wandering all over the place, hoping to find a readable signal – and potentially getting turned off when the don’t find one. We have also recovered a few articles from the old WUN archives as well as from SPEEDX (Society to Preserve the Engrossing Enjoyment of DXing – folded a long time ago) on certain digital related topics, such as discussing how to read an AMVER transmission.

It should be noted that we also sent the amateur radio digital modes to their own page for a very simple reason – while these modes are well understood (and many have their own devoted page that cover their mode far better than we can), the single biggest reason was that these modes can NEVER be encrypted (at least in the US, and likely other countries as well). Sad to say, but there are many modes outside of the amateur bands that we will never be able to read, and some whose purpose is unclear. As of this writing, many UDXF members are noting signals thought to be Russian in origin, utilizing a variation of MFSK-16, a mode generally associated with amateur radio.

Is this document complete? Not even close. It’s designed to be something of an introduction, with enough detail to hopefully draw in both the newcomer and experienced. There are new modes being identified, new networks, and even new players being found all the time. There’s still more work to be done on this, and this is yet another change to the original DigiFAQ- it’s hosted on the RadioReference wiki, where any member (with a free ID) can edit and add to it.

The URL is: http://wiki.radioreference.com/index.php/HF_Digital_Decoding

Regards, Mike

Thank you for sharing this update, Mike!

I receive a lot of questions regarding digital modes even though it’s an area of the hobby where I’m quite weak. I’m pleased that you, Mike, Stan and your team are all working to keep a reference source up-to-date for folks exploring this dynamic part of the radio hobby.

Click here to visit DigiFAQ at RadioReference.com.

WRMI to showcase digital modes via analog radio

31-meter-Spectrum (Source: VOA Radiogram via Richard Langley)

WRMI, Radio Miami International, will showcase digital text and images via analog radio in a half-hour special broadcast to be transmitted nine times (at least), beginning Saturday, 13 August.

The broadcast will mostly be in MFSK32 centered on 1500 Hz. There will also be segments in MFSK64, MFSK32 centered on 2200 Hz, and Olivia 64-2000. The program will include MFSK images, examples of non-Latin alphabets, and an Flmsg transmission. You will also hear “co-channel” music.

To decode the modes on the WRMI broadcast, Fldigi software is recommended. Download it fromhttps://sourceforge.net/projects/fldigi/files/fldigi/ . The main Fldigi website is http://www.w1hkj.com.

And you will use the companion program Flmsg. Download it fromhttps://sourceforge.net/projects/fldigi/files/flmsg/ .

To make Flmsg work with Fldigi, in Fldigi: Configure > Misc > NBEMS > under Reception of flmsg files, select Open with flmsg and Open in browser, and below that indicate where your Flmsg.exe file is located – probably somewhere in Program Files(x86).

For correct decoding of the languages with diacritics, or using non-Latin alphabets, in Fldigi: Configure > Colors & Fonts > RxTx > in the Rx/Tx Character set menu, select UTF-8.

For Fldigi to automatically select the mode and the center audio frequency of the mode, select RxID (upper right of the interface) by left clicking. In newer versions of Fldigi, also right click on RxID and select Passband.

You can decode this WRMI special broadcast as it is broadcast, or from your recording.


Via WRMI’s transmitters at Okeechobee, Florida, except where noted:

Saturday 13 August 0030-0100 UTC on 7730 kHz (285 degrees azimuth)
Saturday 13 August 0730-0800 UTC on 5850 kHz (315 degrees)
Saturday 13 August 1330-1400 UTC on 11580 kHz (44 degrees)
Saturday 13 August 2200-2230 UTC on 5950 kHz (181 degrees)
Sunday 14 August 0230-0300 UTC on 11580 kHz (44 degrees)
Sunday 14 August 2130-2200 UTC on 15770 kHz (44 degrees)*
Sunday 14 August 2330-2330 UTC on 11580 kHz (44 degrees)*
Monday 15 August 2000-2030 UTC on 6070 kHz* **
Tuesday 16 August 2130-2200 UTC on 15770 kHz (44 degrees)

* Preempts DigiDX, usually heard at this time

** Via Channel 292, Germany

Many of these broadcasts will be heard outside their nominal target areas.

Reception reports to Jeff: info (at) wrmi.net

There’s a pattern in that noise!


Many thanks to SWLing Post contributor, @K7al_L3afta, who just shared the image (above) and noted, on Twitter:

“I just discovered the noise at the start of [the VOA Radiogram has] a purpose!” 

That’s a brilliant discovery!

Click here to learn about the VOA Radiogram.

Click here to follow @K7al_L3afta on Twitter.

Update: German communications regulator to allow AM digital modes


As a follow-up to a previous post, many thanks to several SWLing Post readers who noted this news on the VOA Radiogram website:

The German communications regulator Bundesnetzagentur has changed its mind about allowing digital modes on shortwave broadcast transmitters in Germany. Apparently BNetzA thought that Channel 292 was transmitting the text and images in single sideband (SSB), which is how amateurs, military, etc, transmit the digital modes. Now that they know that the MFSK32 and other modes are sent as program audio on an analogue amplitude-modulation shortwave transmitter, their objections were withdrawn.  (It’s similar to A2A modulated CW.)

BNetzA prefers that the term MFSK32 not be used to describe these broadcasts, but we have to specify the mode so that you can set Fldigi or other decoding software to the correct mode. In any case, the weekly MFSK32 transmission will resume on The Mighty KBC, and DigiDX will return to Channel 292.

Meanwhile, VOA Radiogram this weekend will be all MFSK32 except for the transmission schedule in Olivia 64-2000 under the closing music.                       

German regulators prohibit digital modes on broadcast bands


(Source: Kim Elliott via Richard Langley)

VOA Radiogram, 2-3 April 2016: BNetzA sagt nein!

New this weekend is the elimination of the digital text modes from shortwave transmitters in Germany.

The German regulator Bundesnetzagentur has ruled that the digital modes are not allowed in the broadcast bands. Because of this, there will be no MFSK32 on The Mighty KBC this weekend, because it uses a transmitter in Nauen, Germany. And, for the time being, there will be no DigiDX MFSK broadcasts on Channel 292, 6070 kHz, and Radio 700, 3985 kHz.

Listeners in Germany might want to note these arguments for the digital modes on the shortwave broadcast bands:
1) It is broadcasting, not point-to-point communication.
2) It can be received on any shortwave radio, even inexpensive portables with no SSB capability. (Software is required to decode the text and images, but this can be included in future shortwave radios.)
3) DRM is legal on the shortwave broadcast bands, and DRM can transmit text and images.
4) Text and images via analog radio requires less spectrum (bandwidth) than DRM.
5) Text and images via analog radio are a useful new application for underutilized shortwave transmitters and frequencies.
6) Text and images via analog radio extend the range of a shortwave transmitter, resulting in accurate content in conditions where voice transmissions may be unintelligible.
7) Digital modes via shortwave can be a useful alternative when the Internet is not available due to disasters or to net censorship by dictators.

On the same note, SWLing Post contributor, Harald Kuhl, also comments with a news release from DigiDX:

“DigiDX transmissions via Channel 292 (6070kHz) and suspended until further notice. This is due to action by the German regulator Bundesnetzagentur against digital mode transmissions and is beyond our control. Broadcasts via WRMI will continue and we hope to find another outlet to use for transmissions to Europe.”


“Good news – Thanks to Jeff White we have another frequency for this Sunday’s broadcast which should be better for Europe. 15770kHz at 2130. Please can anyone in Europe, North America and elsewhere please send reception reports to reports@digidx.uk for this extra broadcast.”

Sources: DigiDX website & FB