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(Short-, Medium-, Long)wave Radio Meets Digital Stereo
cryptec writes "Today shortwave radio will have some new life pumped into it as the German broadcaster Deutsche Welle will be the first full time shortwave broadcaster of DRM (Digital Radio Mondiale). DRM is a full stereo fully digital broadcast system. The quality of the broadcasts are close to that of FM radio. For samples check out this link." Akai adds this link to an article in the San Francisco Chronicle with some more information, like the involvement of the BBC and Voice of America in this undertaking.
There are in the US people who actually live so far out in the middle of nowhere that shortwave is the only option for radio unless they want to put up a huge antenna.
Its also a fairly widespread hobby. Starting cost can be as low as $10 for a garage sale world band radio up to several thousand for the latest in equipment.
Its pretty fun being able to hear programs from austalia, india, or wherever someone can muster a few kilowatts to bounce a signal off the ionosphere.
Coded Orthogonal Frequency Division Multiplexing
It's similar in purpose to CDMA. It is spread spectrum, sorta. It uses many narrowband carriers transmitting in parallel. The data transmitted on the subcarriers uses forward error correction coding, it's sorta like RAID1 for radio. They can also use tricks like sending the more important data at lower speeds. It's a pretty robust system, but it was mostly designed to combat multipath fade at VHF and above.
I've had enough abrasive sigs. Kittens are cute and fuzzy.
Well, PSK31 doesn't have error checking like DRM does. DRM has configurable "robustness modes" for use in more or less noisy environments.
Did you ask your friend to put the PSK31 signal on the speaker? The really cool thing about PSK31 is that your computer can copy a signal you can't even hear.
(For anyone who's wondering, we're still talking about digital radio. PSK31 is a modulation technique for text which fits a slow TTY-like signal into 31.5 Hz of bandwidth).