Photo by Brock Wegner on Unsplash
Many thanks to SWLing Post contributor, Alan, for his recent article in Radio World titled “The Modernization of Broadcast Radio.” In it, Alan argues that the proposed “AM Radio for Every Vehicle Act” in the U.S. should go beyond preserving legacy systems and instead embrace Digital Radio Mondiale (DRM) as the future of terrestrial broadcasting. Drawing comparisons with digital transitions in countries like Norway, Switzerland, India, and China, Alan highlights the potential to reduce transmission costs, increase coverage reliability, and enhance emergency communications — all while offering a path to modernize U.S. broadcasting infrastructure.
Millions of receivers in cars, and now a new low cost portable has just been released in the Indian market, made in India using receiver module in the UK by very smart hardware and software engineers. It is highly integrated.
None of this is aimed at the USA market which is still using broadcast technology which is over 100 years old. Stay in fairy land.
What is the “new low cost portable” that “has been released”? What is the manufacturer and model? Where it can be ordered?
I have told you before where you can get the DRM1000 module outside of Asia.
There will be none marketed in areas where there are no transmitted signals such as the USA. It will be a waste of money and time.
You will have to go to India and buy almost any new car if you want a car receiver.
https://www.radioworld.com/tech-and-gear/digital-radio/solar-grove-introduces-a-personal-drm-receiver
DRM suffers from several problems. First it doesn’t handle selective fading well. Of course, neither do the current in band on channel digital formats. But if DRM is to take hold, it needs to offer something that the current technology doesn’t have. And right now, I can’t think of anything it does significantly better than the MW AM HD signals.
Jacob,
Selective fading is caused by multiple reflections from the ionosphere and is worst in the high frequency bands. My article is recommending 47 – 88 MHz which is above 30 MHz in the VHF low band which is not usually reflected from the ionosphere, it goes straight through. It is in the broadcaster’s interest to maximise the radiation towards the horizon and in some cases below as well and not send the radiation upwards.
As for high frequency bands the broadcaster should use mode C and D which is designed for selective fading. DRM is sent in bursts to allow for reflections which arrive later to be ignored. Mode D has the longest gaps.
The multiple ‘carriers’ of DRM also have pilot signals added to allow the receiver to measure the relative levels and apply the inverse to an equaliser. The number of pilot tones varies depending on the mode. The critical factors include the signal strength at the receiver, the signal to noise ratio and the MER ratio used in the transmitter.
It is much better than MW because the high frequency audio is present and when stereo is transmitted even in the high frequency bands, reflections do not move the image.
As for HD radio in the AM band, it is almost dead due to the use of adjacent channels to carry the data signal which is about <0.1 % of the carrier power in hybrid mode and in pure digital mode 90 % of the power is the carrier which contains no data.
The DRM audio uses the latest audio compression algorithm xHE AAC® which produces very good stereo sound at much lower bit rates. HD radio uses the old MP3 compression algorithm which has been modified so only HD radio receivers can decode when the royalties for HDRadio® has been paid by the manufacturer. It addition the available bit rate is selected by the broadcaster. In HDRadio® the HD2 – HD4 channels are only 20 kbit/s each. If errors are high the receiver mutes. It is only HD1 which blends back to analog and maybe even analog mono.
Lastly in HD radio the data below the station frequency is identical to that above the frequency, where as in DRM all data is unique allowing for more error correction.
Hopefully North America, can adopt the DRM, if it is found to be the better system! But, now for the transmission towers. Will their height be an obstacle to low flying aircraft, as FM towers are usually built quite high as transmission is “line of sight”..?
This aspect of tower siting is regulated by the US Federal Aviation Administration and hasn’t been a problem here since AM broadcasting began. There have always been tower strikes by aircraft but they are pretty rare.
Michael,
In DRM all of the transmission power is given to the data. In HD radio in the FM band the digital power is a maximum of 4 % of the FM power.
No more E-mails I`m tired of reading them Go Away!
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Interesting.
It’s unfortunate that Digital Radio Mondiale shares it’s Acronym with Digital Rights Management, which is causing a huge disruption of the ATSC 3.0 rollout in the television end of the spectrum.
Why stop with DRM receivers? Let’s also mandate that all cars must be flying, just like the ones from The Jetsons. I know it may sound ridiculous, but in fact, the status of flying cars is surprisingly similar to the one of DRM receivers – only single pieces are known to exist and you can’t actually get any of them from any major store. So it’s kind of hard to foresee lawmakers mandating something that doesn’t really exist on the market.