Category Archives: Digital Modes

Radio Waves: Plant-powered Satellite Comms, BBC Pips, Filter Basics, and Replacing Shortwave

Radio Waves:  Stories Making Waves in the World of Radio

Because I keep my ear to the waves, as well as receive many tips from others who do the same, I find myself privy to radio-related stories that might interest SWLing Post readers.  To that end: Welcome to the SWLing Post’sRadio Waves, a collection of links to interesting stories making waves in the world of radio. Enjoy!

Many thanks to SWLing Post contributors Marty, Dennis Howard, Dennis Dura, Kris Partridge and Richard Langley and for the following tips:


Plant-powered sensor sends signal to space (Phys.org)

A device that uses electricity generated by plants as its power source has communicated via satellite—a world first.

[…]The device can inform farmers about the conditions of their crops to help increase yield, and enable retailers to gain detailed information about potential harvests.

It transmits data on air humidity, soil moisture and temperature, enabling field-by-field reporting from agricultural land, rice fields or other aquatic environments.

The extremely low power device sends signals at radio frequencies that are picked up by satellites in low Earth orbit. It was developed by Dutch company Plant-e and Lacuna Space, which is based in the Netherlands and the UK, under ESA’s programme of Advanced Research in Telecommunications Systems (ARTES).[]

The eccentric engineer: a tale of six pips and how the BBC became the national arbiter of time (Engineering and Technology)

This edition of Eccentric Engineer tells the story of the BBC Time Signal and how, over the years, it has just got more complicated.

Every engineer needs to know the time, if only so as to not miss lunch. Since 1924, many Britons have been checking their watches against the BBC time signal, known affectionately as ‘the pips’.

The history of the ‘pips’ is almost as long as the history of the BBC itself. The first transmissions from what was then the British Broadcasting Company began in late 1922 and soon afterwards there were suggestions of broadcasting a time signal under the control of the Royal Observatory at Greenwich – then the arbiter of time in the UK.

No one seems to have seen a need for this degree of precision, but early broadcasts did use their own ad hoc ‘pips’, marking the 8pm and 9pm news programmes with a time signal consisting of the announcer playing the Westminster chimes on a piano and later a set of tubular bells. This proved rather popular with listeners, who could now adjust their clocks and watches daily, so the BBC decided to invest in some more high-tech clocks from the Synchronome Company. These provided audible ‘ticks’, which the announcer then simply counted down.[]

What Is Replacing Shortwave? (Radio World)

A joint effort is necessary to bring the digitization of radio to a successful end

Analog shortwave will celebrate about 100 years of existence in 2028 when many hope 5G will have been properly defined, tested and applied, though broadcasting is low on its long list of perceived advantages.

It’s true that shortwave was typically a medium of the Cold War that peaked in 1989 and that afterward its listenership dwindled. Many international broadcasters gave up on it as the post-war transmitters got rustier and the energy bills kept mounting.

After all, when budget cuts are needed, no transmitter will go on strike or write to the press, as happened when the BBC World Service tried to unsuccessfully close its Hindi shortwave transmissions in 2011. In 2020 these broadcasts stopped, when committed BBC Indian listeners, writers and thinkers who opposed it in 2011 did not protest too much.

The slow death of shortwave has been blamed on the internet and satellite. As technology and content are inextricably linked, shortwave created its type of content that is no longer favored by the savvy FM listener, internet user and cellphone obsessed.[]

Filter Basics: Stop, Block and Roll(off) (Nuts and Volts)

A casual observer might think that wireless systems consist primarily of filters connected by the occasional bit of circuit! Block diagrams of transceivers often include as many filters as any other function. This is true at the system level, just as it is at the circuit level — and many circuits behave in a filter-like way, whether intended to be a filter or not! That makes understanding filter basics important for wireless success.[]


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DRM30 on a Smartphone: KTWR Shows Us The Way

Image via the KTWR Blog

Many thanks to SWLing Post contributor, Dan Van Hoy, who writes:

[Regarding the reception of DRM via smart phone,] I happened to find this KTWR Guam post about decoding DRM30 with a smart phone, app, and an RTL-SDR:

Convert Smart Phone to DRM 30 HF receiver!

We are pleased to report successful use of an SDR Dongle used to directly receive and Decode DRM 30 over HF today.

The SDR Dongle is an RTLSDR v3 type connected to an android smartphone using an OTG cable (phone or tablet must be OTG capable).

The Software used:
1. Android driver (free)
2. DRM+SDR Android App ($4.99)

The Frequency of the HF broadcast is directly assigned within the DRM+ SDR app with two settings
1. Frequency in Hertz
2. RF Gain (0-512)

Demonstration video showing Clean DRM decode of AAC Audio and Journaline data along with live metadata.  (our signal was very strong, so only a short wire used for Antenna, DX’rs will need an appropriate Antenna)

Now anyone with a smartphone and a $20 SDR can receive DRM 30 HF broadcasts…

Click here to read this post on the KTWR blog.

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Final step for proposed rule to allow AM broadcasters to use all-digital transmissions

Many thanks to SWLing Post contributor, Paul Evans, who notes:

The Federal Register has today published the proposed rule for AM stations to go digital. This is close to the final step.

https://www.federalregister.gov/documents/2020/01/07/2019-27609/all-digital-am-broadcasting-revitalization-of-the-am-radio-service

Comments before 2020-03-09, replies by 2020-04-06.

Thanks for the tip, Paul!

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KiwiSDR update brings integrated DRM reception!

Many thanks to SWLing Post contributor, Mark Fahey, who shares the following tweet from KiwiSDR:

“Happy Holidays. Software update brings integrated DRM receiver (Digital Radio Mondiale) based on Dream 2.1.1 to all KiwiSDRs. Stock BeagleBone-Green/Black based Kiwis support one DRM channel, BeagleBone-AI Kiwis support four. Development work continues.”

Ironically, I had only recently published a post asking if anyone had ever attempted to decode DRM using a KiwiSDR. Turns out, several readers had by porting the IQ audio output into the DREAM application. Now that KiwiSDR will have a native DRM mode, this will no longer be necessary.

Many thanks, Mark, for sharing this tip! As you say, this is “mega news!”

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Cambridge Consultants design a prototype $10 DRM receiver

DRM broadcast (left) as seen via a KiwiSDR spectrum display.

Many thanks to SWLing Post contributor, Michael Bird, who shares the following news via Cambridge Consultants:

Digital launched, ever so long ago, with TV and radio. So what’s the big story? It’s that the last piece of the digital jigsaw is finally in place: a system called Digital Radio Mondiale (DRM), designed to deliver FM-radio-like quality using the medium wave and short wave bands.

We’re familiar with AM on medium wave and accustomed to the horrible buzz, splat, fade away and back again. But it does have a great advantage in that it will reach for hundreds of miles from a single transmitter. That’s a lot easier than FM or DAB, which both need transmitters every 30 or 40 miles. No fewer than 443 DAB transmitter sites are needed to cover the UK alone.

So take a modern digital scheme, apply some clever (and low cost) computing power, and you can get good sound for hundreds of miles. You get to choose radio stations by name instead of kilohertz, and you can even receive text and pictures. Emergency warning and information features are also built into DRM.

Great technology. But will it fly? Is it available for everyone?

The new news is that India, through its national broadcaster All India Radio, has invested in and rolled out a national DRM service, live today. Just 35 transmitters cover that large country. New cars in India have DRM radios in them now. Other countries like South Africa, Malaysia and Brazil are likely to follow India’s lead.

But something’s missing. The radios that can receive DRM are still prohibitively expensive, especially for those markets that would benefit most. So vast swathes of the world remain unconnected to the services that DRM can provide. Where’s the cheap portable that you can pick up from a supermarket to listen to the news or sport?

Cambridge Consultants has just held its annual Innovation Day, where we throw open our doors to industry leaders and reveal future technology. One of our highlights was the prototype of a DRM design that will cost ten dollars or less to produce, addressing that vital need for information by the 60-ish per cent of our global population that doesn’t have internet or TV. It’s low power, so can run from solar or wind-up.

This design will be ready in 2020, available for any radio manufacturer to licence and incorporate into its own products. We’re doing our bit to make affordable radios for every corner of the globe!

Click here to read this post at the Cambridge Consultants website.

Michael also shares this piece from Radio World regarding this project.

I must admit: there have been so many proposed low-cost DRM receiver designs that never came to fruition, it’s easy to be skeptical. I assume the $10/9 Euro design will be for the receiver chip only–not the full portable radio, of course. They plan to bring this to fruition in 2020, so we’ll soon know if they succeed.

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Ongoing DRM tests in Hungary: Could DRM be decoded via a KiwiSDR–?

Budapest, Hungary (Photo by @DNovac)

Several readers have written recently asking about the DRM tests we mentioned in a previous post. These tests are being sponsored by the Budapest University of Technology from June 1, 2019 to May 31, 2020–thus, they’ve been on the air for several months already. 

The programming, which was produced by Radio Maria, is being played in a loop–repeated over and over again. The signal is a modest 100 watts and is being transmitted via a 5/8 wavelength vertical on 26,060 kHz.

This is a low-power DRM broadcast using a very modest antenna, so I suppose it goes without saying that expectations should be in check. It’s a very long-shot for those of us living outside of Europe, of course. With that said, there are a number of KiwiSDR sites nearby Budapest:

You could certainly see the distinctive DRM signal on a KiwiSDR waterfall display, but I’m not sure how you’d decode it.

KiwiSDRs do have an IQ mode, however. I am very curious if anyone has ever used a KiwiSDR to decode DRM, perhaps, using Dream? Could the KiwiSDR IQ be fed into DREAM with a virtual audio cable?

Please comment–have you ever decoded DRM via a KiwiSDR site?


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Hungary conducts low-power DRM tests

Budapest, Hungary (Photo by @DNovac)

(Source: Radio World via Michael Bird)

BUDAPEST, Hungary — Digital Radio Mondiale transmissions began from Budapest, Hungary, last June. Although two Hungarian broadcasters previously tested DRM on medium wave, the transmissions are the country’s first DRM trials on shortwave.

The Department of Broadcast Info-Communications and Electronic Theory at the Budapest University of Technology is conducting these latest trials. Csaba Szombathy, head of the broadcasting laboratory, is also head of the project, which will last for at least 12 months.

While the 11-meter 26,060 kHz frequency is well known for use in local broadcasting, it’s rarely implemented for international broadcasting. […] Researchers have also performed tests in this frequency to measure coverage and determine optimal mode and bandwidth on various occasions in Mexico and Brazil. The new Hungarian trials will add to this research.

Szombathy initially operated the transmitter with just 10 W of power into a 5/8-inch vertical monopole. Radio Maria, a Catholic station, is providing a 25-hour program loop, while a Dream DRM software-based encoder broadcasts the signal using AAC encoding. In spite of the low power, the program was reportedly received in the Netherlands.

In early September, Szombathy moved the antenna and transmitter to a slightly different location to improve coverage. He increased the power to 100 W.[…]

Click here to read the full article at Radio World.

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