Long Wave non-real-time digital radio?

[JasonW]

Hello All,

I am no fan of HD radio. I would, however, like to posit the notion of another, not-yet-existent form of digital radio.

Instead of struggling to cram a river's worth of audio bandwidth into a creek's worth of digital audio bandwidth in real-time and trying to make it sound good, why not broadcast music (and news, if desired) at its full audio bandwidth but at a *lower* data rate to an iPod-type receiver for slightly delayed (a few minutes later) playback?

This would be analogous to the way deep-space probes transmit full-color images (and sometimes audio, from planetary landers) over billions of miles of space using low power, small antennas, and rather low data rates. The data packets are error-corrected before the image (or audio stream) is displayed (or played) later.

In other words, this "iPod radio" would "download" songs and other audio files over the air instead of over the internet. While this delayed radio playback might not be desirable for live radio news, it would be fine for music and non-time-critical news analysis programs.

This type of broadcasting could use the Long Wave band, which is little used in North America except by a decreasing number of aviation Non-Directional Beacons (NDBs). Such an "iPod receiver" would permit true CD-quality audio. -- JasonW

 

[Ai4i]

In this world of "gimme more bandwidth, I need more bandwidth", there is still a lot to be said for narrow bandwidth systems. The most efficient way to send data over the greatest distance with the least power is still extremely slow Morse, and for voice it is SSB.<P ID="signature">______________
Proud 2 B a pioneering satellite radio subs¢riber
Ai4i is always on the trailing edge of technology
______________</P>

 

[JasonW]

> In this world of "gimme more bandwidth, I need more
> bandwidth", there is still a lot to be said for narrow
> bandwidth systems. The most efficient way to send data over
> the greatest distance with the least power is still
> extremely slow Morse, and for voice it is SSB.

I heartily agree--the narrowband FM used for NOAA Weather Radio doesn't sound as good as broadcast FM, but the low-powered NOAA transmitters achieve surprisingly long ranges with listenable signals.

That's what I meant but didn't express well, that a narrowband Long Wave radio signal using a low data rate could be used to feed songs and other audio files to iPod-type radio receivers. Once all of the files were in the receivers, they could play back the songs at full audio bandwidth with CD-quality sound. -- JasonW

 

[Mediafrog]

> why not broadcast music (and news, if desired) at its full audio
> bandwidth but at a *lower* data rate to an iPod-type
> receiver for slightly delayed (a few minutes later)
> playback?

But how long could you keep a delayed stream going? Wouldn't the playback eventually catch up to the live datastream at such a low rate?

> This type of broadcasting could use the Long Wave band

If wristwatches and other small clocks can use the 60 kHz WWVB time reference signal, then I suppose longwave datastreams could be made to work with small I-Pod type devices. But the Longwave band is extremely susceptible to lots of electrical crud, so you need to be in a "quiet" area for it to work well. The issue would be getting a continuous "clean" signal for all the data to be downloaded.

> which is little used in North America except by a decreasing
> number of aviation Non-Directional Beacons (NDBs).

And if you go below 200 kHz, there is very little of anything left. The NDB's are mostly between 200 and 415 kHz, with a few exceptions. I've been hearing of the "imminent shutdown" of these signals for the past decade, but they seem to keep hanging around. I would bet in ten years most of these will be gone.

Of course Europe and Asia still have the Longwave broadcast band, 150-285 kHz.

 

[JasonW]

> But how long could you keep a delayed stream going?
> Wouldn't the playback eventually catch up to the live
> datastream at such a low rate?

It would never catch up at all. Like an iPod downloading songs from a computer connected to the internet, the "iPod radio" would never start playing audio files until they were completely "downloaded" off the air. The receiver would receive all of the data stream of a song (or more likely, a set of songs) and would then alert the user that the file is in the receiver's memory and ready to play. While this was playing, the next set would be in the process of being downloaded into a different section of the receiver's memory.

Long Wave radio propagation is pretty much "ducted" between the ground and the ionosphere--that's why WWVB covers the US like a blanket. Yes, the Long Wave band is noisy in many places, but using a high-power transmitter and a low data rate (with error-correction software in the receiver) would permit CD-quality audio files to be downloaded into the receiver.

Long Wave Non-Directional Beacons (NDBs) will probably be around forever (as well they should--they're simple, cheap to buy and cheap to operate, easy to use, and very reliable), but with their numbers being "culled," more unused channels are opening up in the Long Wave band. -- JasonW