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Digital Radio Mondiale
I am currently working on a single chip, which is capable of receiving and decoding Digital Radio Mondiale DRM transmissions. Even though the standard has been explained in great detail on Wikipedia I wonder who ever gets to read that...So have a look at my personal FAQ:
What is Digital Radio Mondiale?
Have you listened to any AM shortwave radio transmissions lately? No? Why not? Pobably because they sound like crap. However, this crap can be heard around the globe! Unlike your local FM station, which sounds better.The idea behind DRM is that the music is not transmitted "as is" over the existing AM frequencies. Instead, it is send digitally. On the same frequencies.
How does it work?
As you may or may not now... Computers run on 0s and 1s. An MP3 file is basically nothing more than a sequence of 0s and 1s. Let's assume that a high pitched tone represent a 1, and a low pitched tone represents a 0.Now the MP3 can be send over a phone line. That is the same principle a fax machine works by the way! Or over your favourite AM radio station.
Does it really work on just two tones?
No. There are up to 64 different tones. Or something... I dunno... It is encoded by OFDM. Don't ask me how that works.... Look it up at WikipediaDoes it use MP3s?
Nope. Of course not. How big is an MP3? I bet you can burn 12 hours of music on a single CD. But MP3 is ooooooold. Instead, AAC is used to send the mail. Same principle. Different format. With it you can burn 60 hours of music on a single CD. And with the highly specialised HVXC/CELP-format, you can burn over 15 days(!) of your favourite speaches. But those two don't work on music.Why so small?
Decades ago, the only way to talk to somebody on the other side of the world was morsecode. Remember? Dit..Daa.Dit..Da...Dit... Sounds horrible? Yeah. And it was slower that the spoken word. However. Even with heavy interference, one was able to receive a message.Does it REALLY sound better?
Listen for yourself...| - | An AM signal: | amsignal.mp3 |
| - | A DRM signal: | drmsignal.mp3 |
It is the same like DAB, right?
NOOOO!! DAB was designed for FM bands. It requires completely new radio stations. Which are expensive. VERY expensive. Plus, the audio quality is not that much better. So why should the stations even bother investing in this technology? For the "coolness" factor of being digital? C'mon...DRM sounds better than a usual AM transmission. And it uses the same frequencies. All the radio stations need is a single encoder. Which is MUCH MUCH MUCH cheaper than a new radio station.