Many thanks to SWLing Post contributor, Stefano Mollo (VK6WFM), who writes:
I have been lately experimenting with DRM 30, with the aim of coming up with a cheap solution to get on air for next to no $$$, for small, local broadcasters that would either go pirate on FM or would not go at all due to the impossibility here in Australia to get a proper FM license at a cost that does not involves selling a kidney (or two)!
I am a ham radio operator, so I turned my attention to DRM30; [the DRM application] DReaM has the capability of acting as a transmitter as well, so I started experimenting.
Click here to download DReaM via SourceForge.
I was very successful at transmitting a DRM30 / 10 kHz signal with a $ 0.50 TX module otherwise intended to transmit data with an Arduino. The signal was received with an SDR + HDSDR + Virtual Audio Cable + DReaM in reception mode.
So far, so good; with this experiment I realised that DRM 30 can, in fact, yield excellent quality at ANY frequency (as I used the 433Mhz LIPD range in my experiment) or better said, with any medium, as long as it is linear enough to transport the DRM signal.
I wanted to find a way to show the World – literally – what can be achieved with DReaM in TX mode…for free!!!
So, after some trial and error, I have set up the system below which allows anyone in the World to “tune in” my “DRM30 radio station” and listen to my DRM30/18 kHz signal, in full blown stereo. Quality is exceptional, and just imagine to send DReaM’s signal to a proper transmitter instead of streaming it over the internet ….
So…point your VLC Media Player (on Windows) to stream from:
…then pipe VLC’s output to DReaM’s input via Audio Cable (or any other Virtual Audio Cable you like).
In DReaM, select the audio cable output as the sound card’s signal input device:
Then select L+R as Channel:
Set the sample rate to the highest value:
One more thing you need to set is the “Channel Estimation: Time Interpolation” parameter to Linear; this is very important!
After few seconds you should be able my test signal, in full stereo, streamed from a PC running DReaM in TX mode, whose output is then captured by MB Recaster and streamed to an ICE Cast server I have in the Cloud. Note that no particular configuration was needed on the ICE Cast server, at all.
This is an example of what can be achieved on a solid transmission channel with DRM30 and only 18 kHz bandwidth (i.e. the normal bandwidth of an AM channel).
One can achieve the same exact audio quality using any channel linear enough to transport an 18 kHz wide DRM30 signal. It doesn’t matter the frequency, or the physical medium per se.
[…]My aim with this experiment is not to send DRM over IP; there are much simpler ways or streaming audio over IP.
Rather, my aim is to demonstrate what can be achieved with 18 kHz +DRM30 on any frequency and on any medium (which, could be for example the electrical distribution overhead lines …. just saying …. 🙂 ).
If only the local regulator would support this, instead of enforcing draconian regulations … such as the restriction of just 6 kHz on shortwave.
Please share your thoughts.
Fascinating experiment, Stefano! Thanks for sharing!
Post readers: If you’re in the mood to do a little experiment, let us know if you’re able to decode Stefano’s 18 kHz DRM30 broadcast over IP! Please comment!
This is something I have been wondering about
Let’s say I buy a normal cheap SW receiver radio, and I want to tune in to a DRM broadcast in a frequency less than 30 MHz
I would tune in to the DRM station in the normal SW radio receiver, then connect the headphone output of the radio receiver to Line-in of a laptop running Dream
Dream would then decode the Line-in signal to proper audio
Do you think this would work? Or is a standard radio receiver incapable of receiving DRM signals?
As Radio New Zealand International does
The DRM technology in the frequency bands of broadcasting below 30 MHz also allows repetitive linkage in FM, that is, the digital signal is received in the long wave, medium wave and short wave bands and retransmitted by FM signal Analogic instead of taking the signal via internet and / or satellite.
Happy Holidays.
Greetings from Rosario, Santa Fe, Argentina.
It’s called DRM-FM transponder
Jeremias,
Transponders are used in satellites and consist of a sensitive receiver a frequency changer and a power amplifier. Note: The signal is not demodulated and as such if FM is the input so is the output. If the input in TV’s case is QPSK in it will be QPSK out. In both cases the signal is unchanged except for the frequency and the power level.
Translators is the name used for a similar process but on the ground.
On channel repeater can be used in DRM, DAB+ and all digital HD radio where a receiver amplifies the signal, it is converted to in intermediate frequency where it is accurately filtered. This signal is then converted back to the original frequency amplified to a high power and radiated from a separate isolated antenna.
In Australia we have many DVB-S2 satellite receivers in isolated villages which demodulate the signal back to digital signals for TV and a multitude of analog sound channels. The TV signal is modulated into DVB-T for transmission to conventional digital TVs and the sound signals are FM modulated and transmitted to FM receivers. These sites are called retransmission sites.
So your DRM-FM transponder should be called DRM-FM retransmitter.
Mangosman
Jeremias,
Reasonably close to you, high powered High Frequency DRM transmissions will commence in some months time. They will probably be from Brasília, Brazil. The disadvantage will be the transmission of Portuguese and not Spanish.
No mention of the predicted coverage area as yet.
Mangosman
La tecnología DRM en las bandas de frecuencias de radiodifusión por debajo de los 30 MHz también permite enlazar repetidoras en FM, es decir, la señal digital se recibe en las bandas de onda larga, onda media y onda corta y se retransmite por FM en señal analógica en lugar de tomar la señal por internet y/o satélite.
Felices Fiestas.
Saludos desde Rosario, Santa Fe, Argentina.
I wish that posters would do some research before sounding off. In the USA you are lumbered with hybrid HD radio and its poor performance particularly its low power digital signal which surrounds an analog signal with which it interferes. Also the digital signals are in the adjacent channels occupied by other broadcasters. As a result HD1 listening is blended to analog if the digital signal is poor. HD2 – 4 reception stops. Lastly the HD radio in the AM band both hybrid and all digital contain the carrier which is between 67% to nearly 100 % of the transmitted power. The carrier contains no audio at all.
The USA has never comparatively tested HD radio and DRM both in the AM and the FM bands and HD radio will not work on HF radio.
Outside of the USA….
In DRM a few low powered pilot signals replace the powerful carrier, reducing the electricity consumption in the transmitter by at least 60 % and this without providing transmitter cooling which also is reduced.
As far as receivers are concerned India population 1,300 million compared to the USA’s a little over 300 million, now has widespread high powered DRM dual language transmission. Now a number of auto manufacturers are installing DRM radios as standard equipment, including their very small vehicles. They also manufacture DRM radios. See http://www.drm.org . On every weekday, All India Radio nationally transmits DRM only for an hour. These same transmitters transmit AM and DRM in the whole of the one adjacent channel for the rest of their transmissions. There are also 3 high powered digital only DRM in the “AM” band along with HF (SW) DRM transmitters as well.
DAB+ is used extensively in Europe including an analog radio switchoff of national networks in Norway and more than 50 % of listening in the UK using the older DAB. Australian capital cities greater than 25 % DAB+ listening. Many new cars have DAB+ as standard equipment. www. worlddab.org
Stephano should be congratulated for using his ham licence to innovate.
Stephano, How about trying DRM+ in the 6 metre band which is within the 47 – 68 MHz band specified by the DRM consortium https://www.etsi.org/deliver/etsi_es/201900_201999/201980/04.01.02_60/es_201980v040102p.pdf
In the USA, nothing in the current rules prevents an UNlicensed Title 47, Part 15.2xx broadcaster from using DRM on the MW band since such broadcasts are deemed noise within acceptable limits to the FCC. Without adequately performing consumer-grade DRM receivers, reception of those broadcasts does require a mixture of computer and DReaM software, though. Furthermore, decoding of such weak digital broadcasts on the MW band can primarily on be accomplished outdoors with a portable DRM receiver.
No kidding about selling the kidneys on the black market… 😉 Bah, governments love the MONEY and technical excellence must sit in the back seat while money rides in the front.
Yes, DRM is just a terrific radio technology. It can and will be improved slightly, but it’s still excellent as currently standardized. Keep at Stefano!
Thank you Tom, very appreciated 🙂
Cheers, Stefano.
Let me start by saying that, probably, I got it wrong; I’m still wrapping my brain around the “DRM” stuff, so probably I’m missing some details, but… given that you need 18Khz to have a CD quality, stereo transmission, I wonder if, using a (say) “phone” quality transmission it may be possible to reduce the needed bandwidth so that it will fall inside the (allowed) 6Khz, in such a case, and if I got it right, it may be possible to experiment with DRM over ham bands; sure, you won’t have an “HiFi stereo broadcast signal”, but I think that (if it works) it may be a step toward a wider adoption of the DRM
Thoughts ?
Hi Andrew;
yes, you can generate a 5 (not 6) Khz wide DRM30 signal exactly in the same way I did.
And yes, if you feed that 5 Khz wide DRM digital signal into your SSB/USB HAM TX, you will transmit a beautiful, nice and clear DRM30 signal.
Of course, quality will not be CD-like, and it will not be stereo, but still, all considered, it will be impressive.
BUT …..
HAMs have access to VHF and UIHF and above frequencies; there is no reason whatsoever that prevent DRM30 to be transmitted say in 70 cms band. provided that in your country a HAM can transmit with a digital modulation (or any modulation) and with the necessary required bandwidth, then you can simply use non-HF frequencies.
73,
Stefano
Perth, Western Australia.
The thing I dont like about DRM is that it requires a special receiver system… like FM or some other digital modes… Call me old fashioned but if you cant hear it on a 30 cent crystal radio Im just not that interested. AM has done more to democratize radio than any other mode. DRM may be a power saving option that could entice broadcasters but the reception equipment would needs be complicated as well and probably expensive.
No thanks,,, it’s OK for the shack and experimenters, but if the broadcast industry changes over you can kiss low budget short wave listening goodbye. If power saving was an issue then why hasnt SSB taken over the broadcast industry? My guess would be the added expense to receivers that most of the world couldnt afford.
My two cents
joe
…I never said anything about power saving.
DRM is a revolutionary technology that allows stereo, CD quality audio, on Medium and Shortwave or any other frequency.
The receiving equipment is substantially free, but technically not that easy, *for now*.
The fact is that it’s a mature and excellent technology, very cheap to implement, which allows the average person to be on air. And this is certainly something that the big boys of Commercial radio do not want at all. But they cannot stop technology and if they have a problem with that, well, their problem, not mine.
It doesn’t really work as you claim. The specification may be free, but not only is transmitting and receiving not free, from cost or regulation, but also it doesn’t let very many people hear you. The receivers for it are very expensive and, to go by the reviews here, don’t work very well. That doesn’t let you reach the people that most would like. Without a cheap receiver, people in poor economic conditions can’t hear it, so the people using short wave to broadcast to those people (this is most large broadcasters) won’t use it, so the casual hobbyist will only receive it on an SDR because there really isn’t that much to hear, so the radio manufacturers don’t focus on building radios with it in, and the loop continues. It’s great technology from one aspect, but if you can’t economically receive it, then it doesn’t do its job.
In this case, the thing that lets a lot of people go on the air whether the radio industry wants it or not is the internet. To go on air with DRM requires a broadcast license or a willingness to do pirate radio, so essentially what you needed before. The quality improved and the audience shrank, that’s all.
No Laurence, you are incorrect.
One does not necessarily need a broadcasting or transmitter license; it depende where you live;
If you live in Australia, then there are a number of frequencies where anyone can transmit without a formal license or paying anything; same goes for New Zealand and the USA;
Don’t know about the UK or Europe, but I must assume that in every developed country there is a similar “Class/Blanket license” which enables the general public to freely use any transmitter on specified frequencies within certain limits of power.
So, as far as hobby radio goes, DRM + a class license = excellent and legal solution for small / hobby stations, with cristal clear stereo audio 🙂
Receivers are few and expensive, yes, agrees … NOW; like for any new technology, until it is not wide spread, it will be expensive; think the very first color TVs’ or the very first electric cars, and so on.
But this will gradually change and DRM receivers will become cheap as chips, just as today I can get an LCD TV almost for free ….
Once again I must disagree. DRM isn’t brand new. People have transmitted it for quite a while (several years in production, two decades in experimentation) for limited purposes. Similar radio technologies, such as DAB, DAB+, and HD have existed for similar or less time and are much more widely adopted. If cheap receivers were going to be made, I’d expect at least a few experimental and probably terrible models to exist at relatively low prices. However, all the experimental and terrible sets available cost a ton. If they were broadcasting for an affluent audience, that wouldn’t necessarily mean a dead end, but most possible drivers of the technology (read large radio transmitters) aren’t doing that.
About the frequencies available for broadcast, I have absolutely no clue what you’re getting at. If you mean amateur bands, sure it’s free to broadcast on them. However, there are few people with the equipment to receive this other than other licensed amateur operators because people don’t listen to it casually (thus your audience is really small), and this isn’t new as you could transmit an analog or otherwise modulated signal on it before. You can communicate, but not really broadcast unless you want the other users of the bands to dislike you for monopolizing the available bandwidth. Broadcasting to listeners at large requires using a band that can be easily received by them, which isn’t possible without a license, even if they could receive DRM, which they can’t.
I’d really like for DRM to be widely adopted, because it lets high-quality audio be sent over skywave. I want cheap receivers made for people who need to receive the signals but can’t afford something expensive. I have no nostalgia for analog shortwave–if we can replace it with something better, even if it’s more complex, I’m all in. However, it’s wishful thinking to believe that this is happening without considering the roadblocks that it has hit head on.
Stefano: “If you live in Australia, then there are a number of frequencies where anyone can transmit without a formal license or paying anything; same goes for New Zealand and the USA”
Going to have to agree with Laurence N on that one: in practice, in Australia, no there’s not. I won’t speak for NZ, but I suspect it’s not much different.
I had this same discussion, specifically in reference to DRM, with someone else (maybe you?) on a different forum recently. I’ll simply summarise that long, convoluted, very specific post here as:
* LF frequencies are out, due to either power, bandwith/separation, emission type, or transmission length restrictions.
* MW broadcast band is out. You’re simply not allowed to broadcast on the MW BC band at all, regardless of power.
* All HF & VHF frequencies are out, due to either power, bandwith/separation, emission type, or transmission length restrictions. That includes the FM broadcast band’s exception for “Wireless audio & auditory assistance transmitters”, which allows for frequency modulation only.
Now, of course nobody playing with such things here takes much notice of that, & we do it anyway as long as it flies under the radar (i.e. we don’t cause interference, annoy broadcasters, or step on the ham’s toes). But we know it’s not legal, and that doing it legally requires at least a ham or experimental broadcast licence.