Why HD radio is a joke and analog FM broadcasts will stay

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Why HD radio is a joke and analog FM broadcasts will stay

Post by dietermoreno on Sat 10 Aug 2013 - 18:58

Why HD radio is a joke and analog FM broadcasts will stay:

The TL;DR answer is: bandwidth.

Now for the mathematical physics explanation. Warning: simplified science content and simple maths ahead.

The FM broadcast band has only 100 khz per station of bandwidth.

The Nyquist Sample rate requires that in order to achieve an error free symbol rate, double the bandwidth of the symbol rate is needed.

So if the symbol rate is 54 kbps, then 108 khz of bandwidth is needed.

108 khz of bandwidth has exceeded the 100 khz of FM station bandwidth.

So if the symbol rate is 1411 kbps for uncompressed audio, then 2.822 MHZ of bandwidth is needed.

2.822 MHZ of bandwidth has exceeded the 100 khz of FM station bandwidth.

HD radio thus has to make due with less, and uses Windows Media Audio instead of MP3, which WMA has even higher compression than WMA. WMA stereo has only 8kbps.

Thus, 8kbps WMA fits in a 15 khz each side band double side band suppressed carrier FM broadcast sub channel above the stereo signal.

DSL solved the problem by simply adding more bandwidth, so a 54 kbps signal that needs 108 khz of bandwidth if it had 10.8 MHZ of band width it could have a bit rate of 5.4 Mbps.

Unfortunately, the FM band can not just give each station 2.822 MHZ of bandwidth for CD quality, because then there could only be about 5 stations in the approximately 20 MHZ of bandwidth that the FM band covers.

Even giving it MP3 quality would be unacceptable bandwidth.

The analog-to-digital transition worked for TV, but that's because you could never see reference quality to begin with in the first place when it was analog because it used too much bandwidth that could not travel far enough, and so with compression codecs to reduce the bandwidth so the signal will travel farther the TV signal will appear to be a much better quality than you are used to for analog TV, but vastly inferior to the quality of a DVD or bluRay, maybee the same as a YouTube video or NetFlix.


Why would anyone want to listen to an 8kbps WMA broadcast when they can listen to a 320kbps MP3 on their iPods, or listen to the analog signal which is higher quality than the digital signal if you are close to the station?



Conclusion: FM radio isn't going to go all digital any time soon, if ever, at least that is until someone figures out how to compress CD quality into 8kbps.

Either that or expand the FM band to include the low VHF analog television band and the high bandwidth needed to stream uncompressed audio could be fullfilled by the band width of a TV channel the new FM band would be full digital and the old FM band would stay analog to allow for more stations, and the new FM band could be digital simulcasts of existing analog FM stations only for the most popular stations in the area since there would be a limit of 6 digital CD quality FM stations. 320 kbps MP3 compression would more likely be used and it would allow for 4 stations in each TV channel for a total of 24 digital 320 kbps Mp3 FM stations. 160 kbps Mp3 could also be used at a compromise for quality, and that would put the new FM band at the same number of stations as the old FM band which is 50 stations.

but given a choice of streaming 160 kbps from the radio or 320 kbps from a 4G smart phone, which would you prefer?

Thus, by the time the new FM band existed in maybee 20 years from today in 2033, 4G smart phones would probably already be able to stream uncompressed audio and make a 160kbps radio broadcast stream look like a dinosaour.

Conclusion: The whole new FM band in digital on the old low VHF TV band thing isn't going to happen because of the internet.



TL;DR: bandwidth is why.
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Re: Why HD radio is a joke and analog FM broadcasts will stay

Post by AOE_Fan on Sat 10 Aug 2013 - 19:11

Goodbye dietermoreno, I've had enough of your spam.
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