HD Radio limitations

[dnewhous]

I'm curious, what's the max bit rate FM and AM can broadcast in our current hybrid digital situation? The wikipedia only gives bit rates for a hypothetical all-digital world.

 

[Kelly A]

96kbps-FM 40kbps-AM

 

[landtuna]

96kbps-FM 40kbps-AM

Really? The FM digital signal OTA sounds way better than any 96kbps stream over the Net I've ever heard.

 

[Kelly A]

Really? The FM digital signal OTA sounds way better than any 96kbps stream over the Net I've ever heard.

HD Radio does use a relatively low bitrate. With present “hybrid” (i.e., analog+digital) systems, AM HD-R typically runs at 40 kilobits per second. A single FM channel in HD-R is typically 96 kbps. But many FM stations multicast, splitting that bitrate across several HD “streams.” The result in both cases is that the final bitrate is comparable to that for a Web stream.

 

[landtuna]

HD Radio does use a relatively low bitrate. With present “hybrid” (i.e., analog+digital) systems, AM HD-R typically runs at 40 kilobits per second. A single FM channel in HD-R is typically 96 kbps. But many FM stations multicast, splitting that bitrate across several HD “streams.” The result in both cases is that the final bitrate is comparable to that for a Web stream.

So is the total aggregate digital bandwidth on FM HD greater than 96kbps? Your post seemed to suggest it is not, yet it sounds much better than a 96 kbps net stream.

 

[dnewhous]

I thought AM couldn't multicast.

 

[davideduardo]

So is the total aggregate digital bandwidth on FM HD greater than 96kbps? Your post seemed to suggest it is not, yet it sounds much better than a 96 kbps net stream.

Different CODEC

 

[ContinuousWave]

I thought AM couldn't multicast.

It cannot under current IBOC hybrid method...which is why a lot of AMs have been turning off IBOC.

 

[semoochie]

Incidentally, I recently received KRKO Everett WA, in full digital mode, during a test, in Portland OR. It was rock solid and sounded pretty good! When I was dxing about 35 years ago, I could sort of hear it. I don't think you can anymore.

 

[Kelly A]

So is the total aggregate digital bandwidth on FM HD greater than 96kbps? Your post seemed to suggest it is not, yet it sounds much better than a 96 kbps net stream.

As David says, different CODEC plus the audio is processed more and differently than what one would typically find with a web stream. The total digital bandwidth of all IBOC-FM streams don't exceed 96kbps, 40kbps for AM.

 

[Kelly A]

Incidentally, I recently received KRKO Everett WA, in full digital mode, during a test, in Portland OR. It was rock solid and sounded pretty good! When I was dxing about 35 years ago, I could sort of hear it. I don't think you can anymore.

Once Fall starts with shorter days, I can easily listen to out of town AM-HD stations on my car radio in Northern Virginia. Typically those stations are: WCBS-HD, WLW-HD, and WBZ-HD. Unlike some who regularly post on the HD Radio board, given the choice, I'd rather hear the HD signal than the skywave analog.