Dolby FM Broadcasting?

Almost all car radios support HD transmission. Many AV receivers do too. Today there is no need in standalone tuner - no one will buy it. But table radio do have their niche, though still diminishing with proliferation of network media players.

Getting off topic... but sort of. Aftermarket car radios are dropping HD support I think I got the last or second to last model in JVC's "Arsenal" series with HD whenever I bought not the Jeep I have now but the one before that. Ended up pulling it out because I didn't want to lose it. And if you aren't listening through an AVR but your old rack of separates or the little integrated in your spare bedroom (not like anyone we know, right?) you don't have any options.

This seems odd to me as HD radio has the potential to sound good but they aren't targeting the high end at all. I used to thoroughly enjoy one of my local NPR affiliate's subchannels late at night, but if I'm reading in bed or something I haven't had an HD tuner in the bedroom in ages. Don't even know if they're still good or not. Wait, scratch that - just looked, they're apparently off the air (WAMU-HD3 aka Intersection) and their other subchannel is floundering - apparently they were going to get dropped too and some listeners created a foundation to keep it on the air.
 
Huh ... I just bought a new head for the car at Best Buy and they only had one HD Radio in stock. Plan is to hook my trusty old Connect converter to one of he AUX in ports - something I've been doing for years with the stock radio anyway.

hd-radio.jpg
 
Digital radio was a great idea back in 1993 when we were first promised that it was "right around the corner". Unfortunately, just like with digital TV, the U.S. picked a system that was inferior to the international standard, so it took them almost a decade to get it working well enough to be approved by the FCC -- and by the time HD Radio receivers became somewhat widely available in 2005, Internet streaming and iPods had already stolen its thunder.

Especially now that we have thousands of channels and custom music playlists at the touch of a button on our smartphones, public interest in HD Radio remains negligible, and the corporate bean counters are probably going to soon declare it unwanted and obsolete, just like they're doing with CD players, which are also disappearing from the dashboards of many new vehicles today.
 
I'm not real impressed by the sound of the HD signal. That and the dropping in and out makes it annoying if you aren't in a strong reception area. I put some aftermarket stereo in a car my mother had, and as soon as it went digital it was obvious. The sound was brighter and had that characteristic "warble" to it that low bitrate digital sound has. It also popped in and out randomly which got annoying since there was always a second or two of silence as it kicked back in. I found the menu option to shut it off and left it with standard analog capability only.

I guess the Dolby FM thing was an effort to work around the S/N limitations of the MPX system we use? I know I've seen things either with the decoder board, or with connections provided to connect to an external decoder but thats it. Mostly that was about the same time as quad FM was supposed to be the next big thing. I still run several tube based demultiplexers for FM stereo on mono tuners, and I own a couple of AM/FM simulcast tuners so you could say I'm a bit behind the times.
 
I'm not real impressed by the sound of the HD signal. That and the dropping in and out makes it annoying if you aren't in a strong reception area. I put some aftermarket stereo in a car my mother had, and as soon as it went digital it was obvious. The sound was brighter and had that characteristic "warble" to it that low bitrate digital sound has. It also popped in and out randomly which got annoying since there was always a second or two of silence as it kicked back in. I found the menu option to shut it off and left it with standard analog capability only.

I guess the Dolby FM thing was an effort to work around the S/N limitations of the MPX system we use? I know I've seen things either with the decoder board, or with connections provided to connect to an external decoder but thats it. Mostly that was about the same time as quad FM was supposed to be the next big thing. I still run several tube based demultiplexers for FM stereo on mono tuners, and I own a couple of AM/FM simulcast tuners so you could say I'm a bit behind the times.

HD radio only have about 256kbps bandwidth. When more than 2 channels are squeezed into it - don't be surprise with poor quality. If put only one channel into it - sound will be VERY good. As to drop outs - it is also expected. Digital transmission is less than 10% of overall power of FM station. If they used all power for digital only, you would have coverage area much wider than with standard FM (even if consider mono only service).
 
I think all of the local stations had 2 or 3 sub-channels. The main one sounded best, the second and third ones were simply horrible, though of course they were the ones with arguably better programming most of the time.

I'm definitely not one of those "all digital is bad" types, just what I experienced listening to HD radio sounded poor. Heck, I can hear it when radio stations use crappy digital sources over the analog transmission, it sounds like low bitrate mp3 files from back in the Napster days. I don't claim to have magic ears but that warbly digital artifact stuff just drives me up a wall.
 
I liked the content more than the SQ. There might have been services out there that had good predictive playlists but I wasn't using them at the time. Now in my life Spotify kind of plays that role along with some music centric Facebook groups but those weren't a thing a few years ago.
 
HD radio only have about 256kbps bandwidth.

It's even worse than that. The digital bandwidth for HD Radio on FM is 96 kbps, to be divvied up among however many HD streams the station is broadcasting.

On AM it's 36 kbps, with only one digital stream (simulcasting the analog) allowed.
 
It's even worse than that. The digital bandwidth for HD Radio on FM is 96 kbps, to be divvied up among however many HD streams the station is broadcasting.

On AM it's 36 kbps, with only one digital stream (simulcasting the analog) allowed.

96kbps is actual per channel bitrate for two main channels if three streams are used.
 
96kbps is actual per channel bitrate for two main channels if three streams are used.
No, 96 kbps the total maximum bitrate for FM HD Radio, split up among all of the station's HD channels:

http://www.radioworld.com/digital-radio/0014/the-best-process-for-hd-radio-audio/331731

"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."

For example, some valid combations:

HD1 only: 96 kbps
HD1 and HD2: 64 + 32 kbps or 48 + 48 kbps
HD1, HD2, and HD3: 32 + 32 + 32 kbps
 
I apologize if this has been mentioned in a previous post.

Remember that in terms of FM broadcast signals HD means hybrid digital not high definition.

And careful calibration on the receive side (to match the transmitted signal) was needed for the best FM Dolby performance.






 
Remember that in terms of FM broadcast signals HD means hybrid digital not high definition.
According to iBiquity (the company who invented it), the "HD" in HD Radio doesn't actually stand for anything:

https://www.lifewire.com/death-of-hd-radio-534505
Lifewire said:
Unlike HD television, where the HD stands for high definition, iBiquity is on record as stating that the HD in HD Radio doesn't stand for anything. It's just a branding term, and while it's true that HD Radio can offer higher audio quality than analog radio, that isn't always the case.

Calling it "hybrid digital" makes sense now, but the original intent (which will probably never come to pass) was for AM and FM stations to cease hybrid analog/digital operation and transition to digital-only transmission, at which point it will still be called HD Radio even though it's no longer hybrid.
 
seems likely to me as well, there are just too many pieces of analog radio equipment around that would go dead if the switch was made. If that nice alignment generator I bought became a doorstop before I learned to use it properly I'd be awful pissed off.
 
seems likely to me as well, there are just too many pieces of analog radio equipment around that would go dead if the switch was made. If that nice alignment generator I bought became a doorstop before I learned to use it properly I'd be awful pissed off.

I don't know if you can say that with confidence though... Probably more people watch TV than listen to FM, and we did that deal back in what, 2009? I still have a couple converter boxes somewhere, as well as a component HDTV tuner.
 
I wonder what the percentage of OTA TV users are vs the percentage of OTA radio users are though. Even if there are more TV users in the country, a lot of them use some flavor of cable service.
 
I don't know if you can say that with confidence though... Probably more people watch TV than listen to FM, and we did that deal back in what, 2009? I still have a couple converter boxes somewhere, as well as a component HDTV tuner.
That's because the FCC has sold off increasingly large chunks of the former UHF TV band for use by mobile phone carriers. You may remember in the late '80s/early '90s when channels 70 through 83 suddenly disappeared from new TVs -- that's the first time they did that. Back when cell phones were still analog, you could sometimes pick them up by tuning through those upper UHF channels on your TV.

Having both analog and digital TV on the air at the same time meant that each station was taking up two channels (both their original, real analog channel and their new "virtual" digital channel), wasting a lot of band space. After analog TV was forced off the air in 2009, channels 52 through 69 were also sold off for use by mobile data carriers. And now the FCC is planning to sell off channels 37 to 51, forcing almost 1000 TV stations to change channels (so in the coming months, if you watch over-the-air digital TV, you'll probably need to do a channel rescan on your tuner): http://fortune.com/2017/04/19/tv-stations-channels-faq/
 
Try an outboard Dolby B NR box for an encoder, and see if your small transmitter can have the pre-emphasis set to the European standard and you should do just fine. Rethought it out.
Standard US FM de-emphasis is 75uS. European is 50 uS. The Dolby FM uses 25 uS. I still have a Dynaco FM-5 tuner modified to switch between 25 and 75 uS de-emphasis. I lived in Minneapolis in the 1970's where only one FM station, the PBS, broadcast in Dolby FM. The Dolby de-coding can be done outboard easily.

Using European 50 uS de-emphasis for Dolby FM will not work well.
 
The idea was that 25 µS pre-emphasis combined with the extra brightness of undecoded Dolby B NR would end up sounding the same as a standard 75 µS FM signal, on a receiver without Dolby decoding. But with the advent of improved audio processing like the Optimod, FM stations' audio modulation became loud enough that it was above the Dolby threshold most of the time (the Dolby symbol on your tape deck's level meters), at which point there is actually no Dolby encoding or decoding taking place, leaving you with only that 25 µS pre-emphasis, which would sound terribly dull on a standard 75 µS receiver.
 
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