Category Archives: Digital Modes

Guest Post: Decoding WEFAX using an RSP SDR and SDRuno

Many thanks to SLWing Post contributor, Mike Ladd with SDRplay, who shares the following guest post:


Basics to decoding WEFAX using an RSP and SDRuno

by Mike Ladd

SDR I use:
RSPduo from SDRplay using the Hi-Z input. Any model RSP’s can tune WEFAX transmissions. https://www.sdrplay.com/rspduo/

Antenna I use: Megaloop FX from Bonito. In an Inverted delta loop configuration pointed N/E-S/W. Any good antenna placed outdoors should be fine. It’s all about the SNR, not your S-meter reading. https://www.bonito.net/hamradio/en/mega-loop-fx/

Software:

SDRuno v1.32
SDRuno is an advanced Software Defined Radio application platform which is optimized for use with SDRplay’s range of Radio Spectrum Processing receivers.
https://www.sdrplay.com/downloads/

VBcable (donationware) vPack43
Transfers audio, digitally from one application (SDRuno) to another (Black Cat HF weather Fax) with zero loss.
https://www.vb-audio.com/Cable/

VAC (paid for use) v4.60
Transfers audio, digitally from one application (SDRuno) to another (Black Cat HF weather Fax) with zero loss.
https://vac.muzychenko.net/en/
https://www.sdrplay.com/docs/SDRuno_VAC.pdf

Black Cat HF Weather Fax (paid for use) beta 19
Decodes and produces images from the WEFAX transmissions from the output of SDRuno using a virtual audio cable.

Use the discount link available here
http://blackcatsystems.com/register/black_cat_hf_weather_fax_sdrplay_promo.html
https://www.blackcatsystems.com/software/hf_weather_fax.html

Black Cat Uno UDP
UnoUDP allows you control SDRuno’s VFO frequency from within Black Cat HF Weather Fax scheduler. This is done over a virtual com port pair using a virtual com port emulator. http://blackcatsystems.com/download/UnoUDP.zip

VSPE or COM0COM
VSPE is a paid for use app. COM0COM is completely free. Either one of these applications will work. A virtual com port emulator allows you to create a virtual com port. The pair will internally link Black Cat Weather Fax decoder to SDRuno’s using UnoUDP as the transport protocol.

VSPE http://www.eterlogic.com/Products.VSPE.html
https://www.sdrplay.com/docs/SDRuno_VSPE.pdf

COM0COM http://com0com.sourceforge.net/
https://youtu.be/dZg7puQ9Ajk

Introduction:

(some text taken and edited from various website)

This document is not a definitive guide to the WEFAX protocol, the process of decoding WEFAX images or reading a synoptic weather chart https://youtu.be/kzfNSvQREu8. This is only a collection of information that I have found scatter throughout the internet and re-compiled into a document, this document. Expect typographical mistakes, inaccuracies, or omissions.

WEFAX is an analog mode for transmitting monochrome images. It was the predecessor to slow-scan television (SSTV). Prior to the advent of the commercial telephone line “fax” machine, it was known, more traditionally, by the term “radio facsimile”.

Facsimile machines were used in the 1950s to transmit weather charts across the United States via land-lines first and then internationally via HF radio. Radio transmission of weather charts provides an enormous amount of flexibility to marine and aviation users for they now have the latest weather information and forecasts at their fingertips to use in the planning of voyages.

Radio fax relies on facsimile technology where printed information is scanned line by line and encoded into an electrical signal which can then be transmitted via physical line or radio waves to remote locations. Since the amount of information transmitted per unit time is directly proportional to the bandwidth available, then the speed at which a weather chart can be transmitted will vary depending on the quality of the media used for the transmission.

Radio fax data is available from the web on sites such as the ones hosted by the National Oceanic and Atmospheric Administration (NOAA). https://tgftp.nws.noaa.gov/fax/marine.shtml Radio fax transmissions are also broadcasted by NOAA from multiple sites in the country at regular daily schedules https://www.nws.noaa.gov/os/marine/rfax.pdf. Radio weather fax transmissions are particularly useful to shipping, where there are limited facilities for accessing the Internet.

Black Cat HF Weather Fax is a program that decodes WEFAX (Weatherfax, HF-FAX, Radiofax, and Weather Facsimile) transmissions sent from fixed locations around the globe.

A fax is transmitted line by line, typically at a rate of 120 lines per minute, or half a second per line. For example, to send a weather chart, you would start in the upper left corner. You would send the value of that pixel (dot), black, white, or perhaps a shade of gray. Then you would move over one pixel to the right, and send that pixel, and so on, until you reach the edge of the chart. Then you’d move all the way back to the left edge, and move down slightly, one line, and repeat the process.

Each pixel is converted into a certain audio frequency or tone. By convention, a tone of 1500 Hz represents black, 2300 Hz represents white, and frequencies in-between represent shades of gray. So if you listen to a fax transmission, you’ll hear the different tones as each pixel is present. For example, listen to a chart with mostly white background being sent. You’ll hear mostly the high pitch 2300 Hz, and some lower (1500 Hz) blips as each black pixel is sent. When a horizontal line is sent, you’ll hear a long half second burst of 1500 Hz, since the line is all black.

The transmitting station frequency modulates the carrier. That is, when a black pixel is transmitted, the carrier shifts down 400 Hz. When a white pixel is transmitted, the carrier shifts up 400 Hz. For a medium gray pixel, it stays on the assigned frequency. This is how most fax transmissions are made. Since we’re tuning it in SSB, it sounds to us as if the station is transmitting a variable frequency audio tone. The two processes are identical. This accounts for the confusion regarding what frequency to tune the radio to in order to properly decode the fax transmission. Different stations list their frequency in different ways. It is important to remember that a black pixel produces a 1500 Hz tone, and a white pixel produces a 2300 Hz tone within the AUX SP.

The setup works as follows. SDRuno demodulates the received signal. The demodulated audio is piped from SDRuno using virtual audio cable and sends it to the HF weather fax decoder. HF weather fax decoder receives this audio from the virtual audio cable that was demodulated from SDRuno and processes it, producing a picture on the screen

HF weather fax decoder can also set the VFO (tune) frequency of the RSP in SDRuno. This is done over the virtual com port pair using the UnoUDP application as the transport.

SDRuno can internally emulate a Kenwood TS-480, UnoUDP sends the Kenwood TS-480 serial commands via UDP over the virtual com port pair in order to set the frequency selected from the HF Weather Fax Scheduler option over to SDRuno.

You will need to install and configure the following applications.

1: A virtual audio cable.

2: A virtual com port emulator (If you would like HF Weather fax to communicate with SDRuno).

3: UnoUDP (If you would like HF Weather fax to communicate with SDRuno using the virtual serial emulator).

4: HF Weather Fax.

5: A simple wire antenna placed outdoors.

Virtual Audio Cable:

A virtual audio cable allows you to pipe the audio from one application (SDRuno) into another application (a decoder like HF Weather Fax) digitally. I will assume SDRuno is already installed with your device attached and functioning properly.

You can now download a virtual audio cable package.  If you already have a virtual audio cable package installed, you can skip to the next section. If you don’t have a virtual audio cable application installed, you only need to choose one and install only one of the two that are available.

Close any running apps, install the virtual audio cable and reboot your computer. When your computer boots to your desktop, your computer will now have a virtual audio cable pair installed on the system.

You can verify it the installation by going to your Control Panel and double clicking the Sound icon. VB-Cable and Virtual Audio Cable will only install a single virtual audio cable pair, one is for the input (Recording) and one is for the output (Playback). A single pair is all that is needed (as shown below).

Virtual Serial Port:

A virtual com port emulator is only needed if you would like Black Cat HF Fax decoder the ability to tune the station in SDRuno when you double click a station name in the HF Fax Decoder scheduler.

Please use the links provided (additional PDF’s and YouTube videos) on Page 2 of this document for an installation / configuration walkthrough.

You can download my WEFAX frequency bank for use in SDRuno below should you choose not to use a virtual com port emulator. https://signalsacrossthepond.com/download/mike-kd2kog-sdrplay-complete/

Download Black Cat HF Weather Fax and UnoUDP:

Download the latest HF Weather Fax beta package and the UnoUDP application from the link provided on Page 2 of this document. I suggest making one main folder called HFfax and two subfolders within HFfax for each of the applications. One folder is for the HF Weather Fax Decoder and the other folder is for the UNO UDP transport application.

Double click the HF Weather Fax beta ZIP file you downloaded and extract the full contents of this ZIP into the folder you created on your local drive. Right click the “Black Cat Weather Fax” EXE file and send a shortcut to your Desktop.

Double click the UnoUDP zip file you downloaded and extract the full contents of this ZIP into the folder you created on your local drive. Right click the “UnoUDP” EXE file and send a shortcut to your Desktop.

You should have two shortcuts on your desktop, One for the decoder and one for the transport app.

Black Cat UnoUDP:

HF Weather Fax needs a way to communicate with SDRuno, this is done via UnoUDP and the virtual com port emulator.

Launch UnoUDP with the above configuration. Set your UDP Receive port to 58084 and your UDP send port to 58083. UnoUDP must be left running in the background, this will control SDRuno. You can minimize the application or right click the shortcut and have UnoUDP auto minizine on launch.

You should see a Firewall popup prompt asking permission to allow UnoUDP to pass data within the system. You must allow this traffic to pass or external control of SDRuno will not be possible from the HF Weather Fax decoder scheduler.

Assign 1 of the 2 com ports from the virtual com port emulator to UnoUDP (the 2nd com port will be assigned to SDRuno).  My com port pair is Com 1 and Com 2, SDRuno uses Com1 and UnoUDP uses Com 2.

Black Cat HF Weather Fax:

HF Weather Fax needs to be configured in order to communicate with UnoUDP, this is done via the UDP settings. Click “Edit” and “Preferences” Set the UDP Send port to 58084 and the UDP Receive port to 58083.

You should see a Firewall popup prompt asking permission for HF Weather Fax to pass data within your system. You must allow UDP traffic to pass or external control of SDRuno will not be possible from the HF Weather Fax decoder scheduler.

SDRuno:

SDRuno needs its Output assigned to the Virtual Audio Cable. The output can be changed via the RX CONTROL panel, clicking the SETT. button on the top left and clicking the OUT tab.

SDRuno needs a com port assigned so it can be externally controlled. The serial port is assigned via the RX CONTROL panel, clicking the SETT. button on the top left and clicking the CAT tab.

I recommend running the RSP in LOW-IF mode, this is selected via the MAIN panel. This reduces the need to track separation between the Tuned frequency and LO (local oscillator) https://youtu.be/Fsns4P3JxrM

LOW-IF mode also minizines the LO being placed outside of the desired preselect filter of the device in use, Remember the preselect filter is automatically enabled based on the LO frequency https://youtu.be/w-vkiVp7Q4E

I also recommend leaving the IF AGC enabled and placing the RF GAIN as high as possible without causing an ADC OVERLOAD warning within the MAIN panel. If an ADC OVERLOAD warning appears, back the RF GAIN down.

https://www.sdrplay.com/wp-content/uploads/2018/06/Gain_and_AGC_in_SDRuno.pdf

Your first WEFAX decode (Using UnoUDP)

Launch UnoUDP and minimize it.

Launch Black Cat HF Weather FAX.

Launch SDRuno. Set the mode to USB and the filter width to 2.8k
HF weather fax will not set the mode or filter width at this time.

Click the Sked button in Black Systems HF Weather Fax. A current WEFAX transmission schedule will appear. Stations listed in White are either scheduled to transmit or about to transmit based on your computers clock. Stations show in Grey at the bottom of the list are currently off the air or not transmitting.

In the Freq Offset: box enter -1.9 and hit enter (Reason for this is on Page 5).

Click any of the stations listed in the Fax Transmission Schedule and it will automatically tune SDRuno to the correct frequency.

Black Cat HF Weather Fax folder will have a file named “Black Cat HF Weather Fax Docs” Please view this file to understand some of the advanced features available.

Your first decode (Without UnoUDP)

Launch Black Cat HF Weather FAX.

Launch SDRuno.

Navigate to the Memory Panel (MAIN panel and click the MEM PAN button)

Right click the Memory panel and select “Open bank”. Navigate you C drive telling SDRuno the location of WEFAX.s1b

Double click any of the frequencies shown within the WEFAX bank and SDRuno will set the correct mode and tune that station.  My WEFAX.s1b file defaults to the Hi-Z port. If your device lacks a HI-Z input, navigate to the port section within the memory panel, double click the stations port you want to edit and change it to the correct port that’s available or in use for your device. Right click the memory panel and “Save bank” to save the changes.

To use my SDRuno WEFAX frequency bank properly. The MCTR button must be enabled within the RX CONTROL panel, enabling this option allows you to double click and tune a station that is stored within the WEFAX bank. Make sure the LO is not locked in the MAIN panel (LO LOCK).

If a decoded WEFAX image looks blocky or skewed or possibly pixeled, I recommend that the lock output fractional resampler option is enabled in SDRuno. You can enable this from the RX CONTROL panel, clicking the SETT. button on the top left and clicking the OUT tab.

I hope this document helped guide you in getting started with decoding WEFAX transmissions from around the world. I am sure I missed some key features, remember this is only a primer/basics to decoding WEFAX. I do have an accompanying video located here

https://youtu.be/vAYGVimzNX8

Warmest of 73,
Mike-KD2KOG

Disclaimers

SDRPlay modules use a Mirics chipset and software. The information supplied hereunder is provided to you by SDRPlay under license from Mirics. Mirics hereby grants you a perpetual, worldwide, royalty free license to use the information herein for the purpose of designing software that utilizes SDRPlay modules, under the following conditions:

There are no express or implied copyright licenses granted hereunder to design or fabricate any integrated circuits or integrated circuits based on the information in this document. Mirics reserves the right to make changes without further notice to any of its products. Mirics makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does Mirics assume any liability arising out of the application or use of any product or circuit, and specifically disclaims any and all liability, including without limitation consequential or incidental damages. Typical parameters that may be provided in Mirics data sheets and/or specifications can and do vary in different applications and actual performance may vary over time. All operating parameters must be validated for each customer application by the buyer’s technical experts. SDRPlay and Mirics products are not designed, intended, or authorized for use as components in systems intended for surgical implant into the body, or other applications intended to support or sustain life, or for any other application in which the failure of the Mirics product could create a situation where personal injury or death may occur. Should Buyer purchase or use SDRPlay or Mirics products for any such unintended or unauthorized application, Buyer shall indemnify and hold both SDRPlay and Mirics and their officers, employees, subsidiaries, affiliates, and distributors harmless against all claims, costs, damages, and expenses, and reasonable attorney fees arising out of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized use, even if such claim alleges that either SDRPlay or Mirics were negligent regarding the design or manufacture of the part. Mirics FlexiRFTM, Mirics FlexiTVTM and MiricsTM are trademarks of Mirics .

SDRPlay is the trading name of SDRPlay Limited a company registered in England # 09035244.

Mirics is the trading name of Mirics Limited a company registered in England # 05046393


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DRM: a solution to the “medium-wave problem”–?

(Source: Radio World)

Is medium wave in decline? Some people think so.

In the 1950s radio was declared mortally wounded by TV. But then FM with its new music rescued it, becoming one of the most successful technologies and platforms ever. Radio survived and thrived but AM should have died at the hands of the nimbler, younger and more attractive FM.

Only it did not and the medium reinvented itself by using presenter-led programming, commercial music and sport. In the United States it took until the end of 1990s for the FM and AM audiences to be equal and to this day the big AM stations are going strong, bringing in the ad dollars.

REASONS

Still, it’s undeniable that the whiff of decline has enveloped AM in the past two decades. The reasons are well-known: Analog medium wave doesn’t always deliver the best sound, it can suffer from interference, it can behave annoyingly different by day and night and even by season. Medium wave mainly appeals to a maturing population (a global phenomenon, considered shameful by some!) using aging receivers (this is bad!).

[…]

THE SOLUTION

Recently cricket fans were able to enjoy an open-air demonstration of three different DRM programs on one frequency ahead of an important match in Bangalore. The fans also received data (stock exchange values) available on radio screens. This demonstrated that digital DRM is a game changer for medium wave.

In DRM the crackling audio disappears as sound is as good of that on FM. The electricity consumption and costs decrease, the spectrum is trebled and reception, even in cars (as available in over 1.5 million cars in India currently) is excellent, too.

If it is so good then why isn’t DRM medium wave conquering the world faster? Maybe it’s about confidence in a new platform. Broadcasters and governments need to market DRM digital radio once signals are on air in their countries.

As for receiver availability and their costs, let us remember how many receivers were on sale in the 1970s when FM was taking over the world. Nowadays, many listeners consume radio in their cars rather than sit in front of a retro looking wooden box. Digital receivers (DRM alone or DRM/DAB+) are a reality and a bigger push for digital would help with volumes sold thus bringing down the prices.[…]

Click here to read the full article at Radio World.

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Mike’s tips for decoding SW Radiogram broadcasts

Many thanks to SWLing Post contributor, Mike (KA3JJZ), who writes:

Have you ever heard of the SW Radiogram digital broadcasts? These are produced by Dr. Kim Andrew Elliott and started way back when as the VoA Radiogram. They are now carried on 2 other stations (WRMI and WINB) on a schedule (check every week for a summary of images) that you can find on the SW Radiogram website;

https://swradiogram.net/

These tests consist of both text and images. Currently MFSK32 and 64 have been used, and an occasional ‘secret’ mode has been slipped in at the end of the transmission. The last time this was done, the mode was PSK125R.

You might ask how you can receive these broadcasts, and what you need to decode them. We have 2 wiki articles that go into great detail – one for PCs, and one for Android devices – here;

https://wiki.radioreference.com/index.php/Decoding_the_SW_Radiogram_Broadcasts

https://wiki.radioreference.com/index.php/Decoding_the_SW_Radiogram_Broadcasts_with_TIVAR

Yes, you can copy these broadcasts using an Android powered phone or tablet using an application called TIVAR. John VK2ETA has written a quick start guide which is available on the SourceForge website as well as the RadioReference wiki (the links are provided in the article)

These articles are written for folks who are just getting their feet wet, so the above articles touch on radios (no, you don’t need to use an expensive radio, though many do), antennas, propagation and more. The most popular software is FLDigi, but if you happen to have MultiPSK or DM780 (part of Ham Radio Deluxe), they can be used as well. Links are given for the software and any available support.

Along with Tumblr, SW Radiogram has both a Facebook and Twitter page (where members often post decoded images) here…

https://www.facebook.com/groups/567099476753304/

https://twitter.com/swradiogram

Thank you, Mike! Yes, I’m a big fan of the SW Radiogram–the community that has formed around this particular shortwave program is quite amazing. Thanks for all of the tips!

Click here to view the SW Radiogram website.

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Gospell product lineup for IBC 2019 includes the GR-22 portable DRM radio

Many thanks to SWLing Post contributor, Ed, who writes:

SWLing Post readers might be interested in learning about Gospell’s newly-announced DRM receivers and active antenna products. The GR-22 “pocket-sized” “full-wave” receiver that’s supposed to be available for purchase by June 2020 seems especially interesting.

(Source: Gospell Press Release)

Gospell to announce the DRM monitoring system and imminent release of portable DRM receiver, and more

Chengdu, China – Gospell, a leading supplier of pay TV system and equipment, satellite TV receiving products and microwave products, announces its product lineup for IBC 2019. The company will debut several new products featuring DRM (Digital Radio Mondiale) for both consumer and industry market, including:

    • GR-22 – Portable DRM/AM/FM Receiver
    • GR-227 – DRM Car Adapter
    • GR-301 – DRM/AM/FM Monitoring Receiver
    • GR-310 – Audio Broadcast Monitoring Platform
    • GR-AT3 – High Performance Active HF Antenna

GR-22 is a sleek and classy portable radio from Gospell, the contemporary stylistics of exterior design fits in your personal style, crystal clear DRM digital radio and AM/FM brings practicality and comfort to your daily enjoyment. Despite its pocket-size, it’s a nifty full wave band receiver packed up in a tiny body that enables you to explore a wide variety of radio stations. It is also future-proofed for the next generation DRM-E technology. You have access to all the presets, station names, program details and even Journaline news on the easy to ready large LCD in a simple and intuitive way. Sleep timer set your radio to automatically switch off or wake up at your convenience. Listen to your favorite radio programs anywhere you like with 4 x AA batteries or connect it to mains. GR-22 is a multi-functional radio that is flexible to your listen habits. GR-22 will be available for purchase on Q2 2020.

GR-227 is a car digital radio adapter that utilizes most advanced interference and noise cancellation technology to receive digital radio in car while achieving the best audio quality and serve it to the car audio system over aux cable or by transmitting over an unused FM frequency. The receiver is fully compatible with DRM standard that is being deployed over the world, with its latest audio codec xHE-AAC. Based on software defined radio technology, GR-227 is ready for the emerging DRM-E standard that extends the DRM broadcast to FM band.

GR-301 is a high performance monitoring receiver that supports DRM, AM and FM. GR-301 supports the collection of key parameters of audio broadcasting, including SNR, MER, CRC, PSD, RF level, audio availability and service information. The collection and uploading of parameters meets DRM RSCI standards. The GR-301 can work independently or be deployed with other receivers to become a node in the service evaluation network. The GR-301 supports the xHE-AAC audio codec and is capable of handling the latest DRM-E standard through software upgrades.

GR-310 is a management platform designed for audio broadcast monitoring and receiver control purposes, it manages the geographically distributed GR-301 receivers. The platform can formulate receiving schedules, configure the receivers to perform receiving tasks, perform real-time browsing of the reception status, store historical data, and visualize the statistic data in a intuitive way. In addition to monitoring and analyzing data, the GR-310 platform also supports real-time audio monitoring and configuration of alarm conditions, alarms will be triggered when rules are met.

GR-AT3 is a high-performance active monopole antenna with reception frequency ranges from 0.3 to 50MHz. It is designed to work in harsh environments with respect to strong man-made noise and stern natural conditions. It is compact and easy to install, supplied accessories enable rapid installation. The antenna is comprised of a wide band amplifier in an IP67 waterproof aluminum body together with an active element made of a stainless-steel. The solid construction ensures durability and maintenance-free operation.

“We’re constantly working to ensure we’re bring the latest technology in our product”, says Haochun Liu, assistant to general manager, “These products underscore the Gospell’s commitment to providing easy access to high quality information at affordable prices. Both consumer and industry can benefit from it.”

Gospell will be exhibiting at IBC 2019 in the Amsterdam International Broadcasting Convention (IBC) Hall 3 C67, September 13-17. To schedule a meeting at IBC 2019 or access a sample of the featured IBC showcase, email haojq@gospell.com

About Gospell

Established in 2001, Gospell Digital Technology Co Ltd (GOSPELL). is a hi-tech enterprise with R&D, manufacturing, business consultancy and planning, trade, delivery, project implementation and after sales service, acting as a complete DTV and triple-play solution provider for Digital TV/OTT related projects. Headquartered in GOSPELL INDUSTRIAL PARK at Chenzhou, Hunan Province for CPE related production manufacturing, GOSPELL also has its office in Shenzhen for business/marketing management and administration, in Chengdu for R&D and headend/transmitter system production/debugging and Customer Service Center, and in 12 cities in China as well as international offices in India, Africa and Mexico.

Thank you for sharing this, Ed. Looking through the press release, I don’t see any DRM radios where they note shortwave reception, however, the GR-22 is being called a “full wave band receiver.” Perhaps “full wave” is their way of indicating shortwave reception?

It looks like the GR-22, and all of the products listed above, are squarely targeting the new DRM market in India.

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“Pirate DAB multiplexes take to the air in Dublin and Cork”

(Source: Radio Today Ireland via Mike Terry)

Pirate radio stations are appearing on unlicenced DAB digital multiplexes in Dublin and Cork, and more are planned for other cities in Ireland.

The “FreeDAB” platform, now carrying around ten stations, was born out of frustration over the procedures in place to broadcast legally on DAB in Ireland.

During the recent 12-month legal DAB multiplex trial operated by ‘éirdab’ in Cork, a radio station wanting to broadcast via this method would need to pay upfront for a five-year Section 71 licence (a list price of €14,000 (plus VAT)) and wait up to five months for the application to be processed.

But waiting five months for a licence and paying five years up-front to be on a 12-month trial are just two of the issues holding back DAB in Ireland.

The technology required to broadcast a multiplex is now easier to acquire and is mostly controlled by software whilst costs to broadcast illegally via the multiplexes also appear to be very low.[…]

Continue reading the full article at Radio Today Ireland.

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WSPR explained

Many thanks to SWLing Post contributor, Bill Patalon, who shares a link to the following article on Extreme Tech:

Last Tuesday at 1744 UTC (1:44 PM EDT) UR3RM, a ham radio station in Ukraine blindly sent out a message on 7040.138 kHz.  It was automated. It was text. Maybe someone would hear it. Maybe not.

The “maybe not” part is easy to understand because UR3RM’s transmitter was putting out one milliwatt, .01 watts. To put that in perspective, a Class 2 Bluetooth transmitter, the ones good for around 30 feet, run 2.5 milliwatts.

UR3RM was using a mode called WSPR for Weak Signal Propagation Reporting. Unlike most of ham radio, this is a one-way mode. Not only is there little expectation anyone will be listening, but there’s even less that the signal would make it back. Radio propagation isn’t always a two-way path.

WSPR’s biggest selling point is you can do it on the cheap. It’s easy to set yourself up for not much more than $100 and often a whole lot less. And, though a ham radio license is needed to transmit, anyone can put up a receiver. And the US ham license test is multiple-choice, all published and online.[…]

Click here to continue reading at Extreme Tech.

Post Readers: How many here have received and/or transmitted using WSPR?  Please comment!

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“North Korea Resumes DRM Broadcasts”

(Source: Radio World via Michael Bird)

North Korea has returned to digital radio broadcasting after an absence of nearly two years.

The latest Digital Radio Mondiale (DRM) shortwave transmissions began mid August. The country has had periodic DRM broadcasts for many years.

It appears unclear at this time however whether the current series of transmissions will soon end or be the start of a regular service.

Thus far, all of the latest test transmissions have taken place on 3560 kHz, which is actually allocated for amateur radio use.

According to radio enthusiasts in the region, the signal has been clear and very audible.[…]

Click here to read the full article at Radio World.

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