(Source: DRM Consortium)
A new era begins for Brazilian radio broadcasting with the arrival and installation of a first shortwave digital radio DRM transmitter developed and manufactured in the city of Porto Alegre by BT Transmitters. The transmitter will be sited at the public broadcaster (EBC) Rodeador Park, near the capital Brasilia, to be connected to one of the huge HF antennas of EBC (National Amazon Radio is transmitted from there).
The equipment (a transmitter of 2.5 kW) will be tested on an experimental and scientific basis with the help of the University of Brasilia (UnB) and the Ministry of Science, Technology and Innovation.
The National Radio of the Amazon broadcasts from Brasilia especially to the Northern, Amazonian region of Brazil. The signal will be also available in the neighbouring countries to the north of Brazil. This is primarily a domestic shortwave digital project aimed at the Amazon where about 7 million riverside and indigenous people live. They are far from any other means of communication as there is no mobile phone or internet coverage.
Rafael Diniz, the Chair of the DRM Brazilian Platform, thinks that: “Shortwave digital radio (DRM) for the Amazon region will ensure a new level of communication and information as Nacional’s programming is both popular and educational. It brings audio and much more at low energy cost to whole communities there. With the adoption of digital radio, one of the major problems, that of poor sound quality affecting at times shortwave, will end. Listeners will be able to enjoy DRM broadcasts in short wave with a quality similar to that of a local FM station together with textual and visual multimedia content.”
“This is a huge step forward, says Ruxandra Obreja, DRM Consortium Chair, “not just for Brazil but for the whole of Latin America. When everything else fails or does not exist, DRM will provide information, education, emergency warning and entertainment at reduced energy costs.”
Click here to read this article at the DRM Consortium website.
As a side note, I do hope the DRM Consortium or the University of Brasilia and the Ministry of Science, Technology and Innovation somehow make DRM receivers available to the “7 million riverside and indigenous people” they hope will eventually benefit from their broadcasts. At this point, however, this sounds more like a university experiment similar to those conducted at the Budapest University of Technology in Hungary.
http://drmnainfo.blogspot.com/2020/09/details-on-radio-nacional-da-amazonia.html will give you much more information
Much more information on the Brazilian experiments
http://drmnainfo.blogspot.com/2020/09/details-on-radio-nacional-da-amazonia.html
Whilst the power is low, the antenna gain is high and there are plans for much higher power, more than Radio New Zealand Pacific which is covering the South Pacific Ocean, and over spilling into the USA on occasion.
I hope this isn’t a project to determine if the DRM could service isolated communities; that is bound to lead to failure. The radios are power hungry and the signal iffy. Instead, perhaps they should do what RNZI does and use the DRM to feed FM transmitters at strategic locations. A few solar low powered FM transmitters fed by DRM shortwave in villages would bring a lot more to the table
Firstly,
This project is not designed to be a broadcast service. It is to find out the characteristics of the ionosphere over the Amazon. As a result they will then know how much power is required.
Secondly,
On this site they are talking of SDR receivers demodulating analog signals. You are not complaining about the power consumption of those receivers. Most new DRM receivers are SDR receivers. What is the actual power consumption? This was also the charge made of DAB receivers. When investigated the person who measured it had no receivable DAB signals so the power value was not real. Power consumption drops as specialized chips designed for specific tasks use much less power
Thirdly,
The Amazon is a huge area. a 2.5 kW transmitter in the MF band in the USA doesn’t cover much area.
Fourthly,
Radio New Zealand International DRM is transmitted at 50 kW average power, and remember that the 67 – 100 % which is the carrier in an AM signal is not used.
Your information about modern DRM receivers is out of date. https://www.inntot.com/drm-software-receiver-stack/ Have a listen to the BBC example is over a distance of 3182 km from Singapore to Southern India using a set of stereo speakers or headphones.
Much more information on the Brazilian experiments
http://drmnainfo.blogspot.com/2020/09/details-on-radio-nacional-da-amazonia.html
Whilst the power is low, the antenna gain is high and there are plans for much higher power, more than Radio New Zealand Pacific which is covering the South Pacific Ocean, and over spilling into the USA on occasion.
Another nice piece of flowery propaganda from the DRM consortium. During the early stages of the Covid crisis I spent many weeks listening to DRM broadcasts around the world via Kiwi SDRs and direct here in Hong Kong using my SDRPlay and the DRM+ SDR app on my Android phone. I can say one thing with absolute certainty: DRM requires nearly perfect conditions, high power (bare minimum 50KW) and a good receiver with good antenna on the users end. 2.5KW simply will not work, especially in this period of poor SW propagation unless it was some type of NVIS arrangement for a nearby audience. Even then, results will vary.
As Thomas suggests, you still have the affordable receiver problem. There aren’t any. Only photos and promises, many of these already broken. It’s a chicken and egg situation that may never be resolved. The world is not crying out for more DRM and DRM radios for many obvious reasons. A good old-fashioned AM/FM/SW radio for about $10 works just fine. You can buy them on the street here in Hong Kong. The KISS principle (Keep It Simple Stupid) applies in radio too. Radio can be simple, cheap and useful. The same may never be said about DRM.
Dan,
How much of your listening was from India? DRM has 35 high powered DRM transmitters up to 500 kW in the medium frequency band. Where are these SDR receivers in relation to the coverage areas of the transmitters?
They transmit two programs from a single transmitter along with emergency warnings for monsoons etc which contain detailed text and images. This is not possible with AM or FM.
What about the new Siberian DRM transmitter using a purpose build DRM receiver in Hong Kong?
I suggest that living with 1910 AM technology for MF and HF and with 1935 technology for FM is fit for purpose anymore. In Norway there is no longer any AM or FM radio, only DAB+. Many countries and Europe have switched off AM transmitters and many high frequency (AM) transmitters as well due to the high cost to broadcasters.
I notice you are not saying the same things about DAB+ where 82 million receivers have been sold. The signal processing is virtually identical to that in DRM. A DAB+ transmitter transmit usually around 18 program which is a huge cost saving. DRM above 30 MHz can do this too. In addition DRM does not have the energy wasting carrier of AM where between 67 – 100 % of the transmitted power contains no sound or information.
So if the receiver is an SDR all that is required is to add the decoding firmware for DAB+/DRM and add a display for the images and text.
Mr. Mangoman I’ve read your previous comments about DRM. Seems you comment any time there’s a possible opening for promoting DRM. Guessing you might be with the DRM Consortium?
Instead of simply talking about the virtues of DRM I suggest you share some information about how you successfully decode it at your QTH. What equipment do you use? I recall someone else asking you this and you didn’t reply. Have you ever even tuned to DRM?
I assume you must be with the consortium and feel an obligation to defend the mode. If you are with the consortium, say so. It’s okay.
Share your real world observations, logs, and maybe describe your reception setup. What works for you? Recordings would be good. Like Dan, I’ve had very little fortune decoding shortwave DRM even when I use my WinRadio and switch between a number of my SWL and ham antennas. Once got 5 monutes of clear VON DRM copy and about fell out of my chair. Rare stuff! Share your knowledge with us instead of reciting DRM specs please. Ask Thomas if he could post your stuff in a guest article. I bet he would.
Hi, John,
I don’t think Mangosman is affiliated with the DRM Consortium, but he’s obviously passionate about DRM and other digital modes used in broadcasting.
Of course, I’d be more than pleased to post how-to articles about achieving stable DRM reception.
In terms of DXing, I agree that it’s no where near as effective at blanketing the globe as good old AM and SSB modes.
Cheers,
Thomas
No, Alan’s just a rabid fanboy with a long and odd backstory. Not much of it is very flattering to him, so I’ll bite my tongue on that until an appropriate time. Let’s just say he’s got a long history of being very wrong, very insistently & belligerently…
Alan and I have butted heads over digital encoding and broadcasting technologies for nearly 2 decades. AFAIK he’s never actually received any DRM himself, aside from maybe via webSDRs (and he didn’t know KiwiSDRs could receive and decode DRM until somebody else enlightened him on a DRM mailing list the other week).
I notice that many of the posters are from the North America which have no DRM broadcasts aimed at that continent. The only DRM broadcasts from that country are aimed at Cuba from North Carolina. (USA Government Radio Marti)
I also live in a location well away from any DRM coverage areas. Most High Frequency broadcasters use directional transmitting antennas to maximise their signal strength into their target areas.
I am not part of the DRM Consortium. I have worked in the technical side of a national broadcaster including passing exams in transmission for more than 20 years.
I am critical of HD radio because it uses the transmission channels of other broadcasters resulting in very low powered digital signals, hence poor digital coverage area compared to their analog area.
There are chips available which can demodulate all frequency bands, and decode DAB+ DRM, AM and FM, we need this in all new radios. I have omitted HDradio because outside of the USA no one wants to pay licence fees to xperi for broadcasts we will never have to receive. In Europe DAB+/FM receivers do not cover AM. The advantage of a receiver which will work anywhere in the world is what you get with AM/FM receivers (SW broadcasters all use AM). We need a digital version of that. DAB+ is good in high population density and DRM for all areas.
I do live where we have had high powered DAB+ for 11 years (We were the first country to do so and it is widespread now in Europe to the point where Norway has switched off network AM and FM). The signal processing in DAB+ and DRM is nearly identical.
I have a pocket DAB+/FM receiver and at a location where the DAB+ starts to breakup, the FM signal is in mono and hissy. The AM broadcasters transmit the same program on DAB+ in stereo and the missing high audio frequencies. It sounds great.
I was pilloried on another site about the sound quality on DAB+. When challenged the main poster could not describe the effect on the sound, state program/musical piece with problems. Now commercial broadcasters are using an even lower bit rate! The number of listeners continues to rise!
Before I mention reliability, I rely on measurements and side by side comparison rather than an impression from a few chance receptions where the conditions are unknown as an example http://s836646369.websitehome.co.uk/public_html/R15-WP6A-C-0299!P1!PDF-E.pdf
Improving reliability. At a radio frequency level, the type of modulation is irrelevant. Receivers need a filter which is tuned on the frequency of reception and the bandwidth being that of the signal. Radio Frequency amplifiers can overload producing intermodulation distortion that causes out of channel interference to be translated into the channel of interest. Software Designed Receivers use a local oscillator and mixer, just like analog radio but the frequency of the oscillator is very close to that of the signal being received. The result is a frequency close to audio. Out of channel interference in analog results in inaudible frequencies but in digital signals this causes errors and hence unreliable reception. This means RF filtering is important. The next stage is an analog to digital converter, whose linearity is improving making reception more reliable.
The RF, oscillator, mixer and ADC must be shielded from any computer doing decoding because of the interference radiated by the computer and also dedicated decoding chips.
Using directional aerials as discussed on this site is also useful.
For maximum reliability you need a receiver designed specifically for digital reception. In the DRM case you need a newer one so that it will decode xHE-AAC audio.
Lastly go to an area which is in the coverage area of a DRM station, the North Island of NZ is nice, India, hopefully Brazil, once they get their 100 kW transmitters on air
I must agree, Dan. In fact, I recently said much of the same thing in another comment thread:
https://swling.com/blog/2020/09/cant-receive-anything-on-your-new-shortwave-radio-read-this/#comment-650252
It sort of amazes me sometimes how I’ll receive a strong DRM signal (esp. as compared with AM carriers) but can’t get a decode, save the Newsline data. Other times, I can decode the DRM audio but it just not good enough for 100% copy. Typically it’s closer to 50% copy and there’s nothing more frustrating than trying to enjoy the actual content of a broadcast and it drop out.
There are exceptions: VOA targets Cuba with DRM broadcasts and I’m sure even a portable could easily pick up the signal there. And, yes, in India via the local radio networks you can decode DRM.
But over HF/shortwave? I’ve personally had very little luck. As you say, it requires near ideal conditions. When it works, it’s fabulous, but most of the time it does not.
-Thomas
The comparison with the Hungarian University is unfair.
Firstly 2 500 Watts is much more than the 10 then 100 W.
The frequency used in Hungary is in the 26 MHz band which is not suitable for covering the huge size of the Brazilian Amazon. Much lower frequencies are more likely to be used for this large coverage area.
I should have been more clear. I was only pointing to the fact that it’s a DRM experiment in partnership with a university. This one in Brazil will have a proper HF antenna as well. If I recall, the one in Hungary was a very modest antenna.