HD Radio Self-Noise

[Mikey Radio]

That brings up the question of whether radio or TV transmission facilities will even be needed in the future. In other words; if consumers consume radio programming via their ubiquitous smartphones which is the way they run their lives anyway, why should radio or TV bother with traditional transmission gear, tower/land leases, and all the utilities and maintenance plus licensing required to keep it all running?

To that point, even my 2017 General Motors vehicle (so 6+ year old technology now) has the ability to act as a WiFi "hot spot", so every passenger in and around the vehicle can connect their smart phones or mobile devices to the infotainment system and stream or use the internet or apps via high-speed WiFi...Though it does come with a monthly fee. Again, that's technology that's already 6 years old. If newer cars could connect up to satellite and/or cell data, and allow the driver to select content they want via the in-dash infotainment center (podcasts, Apple Music, Spotify, etc) that would eliminate the need for a cell phone with that content to be connected, AND it would virtually eliminate the need for OTA AM/FM radio for many. This may already be available; the last time I went "new car shopping" was a few years ago.

 

[Brian Bowers]

"However, if HD is playing havoc with its analog counterpart, where's the FM analog audio quality benefit?"

I don't think anyone is saying it is.

I believe that's what the OP's ham-radio.com HD Radio Self-Noise study is showing/proving. There are two soundfiles provided in the link where you can actually hear it. I believe I'm also hearing it in my local area. Guaranteed most listeners wouldn't notice or care, so except for a few;, you're right, it's probably a "nothing-burger", which is probably here to stay. If this is indeed what is happening to FM analog transmission with HD; I do find it discouraging from an engineering standpoint.

I also wonder if any major FM radio broadcasters will in the future turn off their FM HD signals as a way to save money. They've made cutbacks in every other department; I wonder if this one is next?

 

[rustyhodge]

A theory I have (and it is mine) is that people vary considerably in their sensitivity to digital artifacts.

I've also found that people who have non-linear hearing or can't hear certain frequencies are also prone to hearing artifacts more which makes sense given that the whole premise of perceptual codecs is masking artifacts. But if you can't hear the frequencies that mask the artifacts, then you're only hearing the artifacts.

This is also true when listening to digital audio on very poor quality speakers or headphones, for me at least. Same thing with club DJs who tend to use EQ to extremes at times for effect, it makes the otherwise-masked artifacts stand out.

I think part of that is that he has perfect pitch (and I don't). He pretty much can't stand digital anything other than uncompressed formats.

I'm curious to do some A/B testing with 128k AAC, 256k AAC vs lossless audio. I think the majority of people equate 128k with MP3, which also almost everyone can tell a difference from uncompressed sources.

But I was at a high-end audio show a decade ago, and a vendor had one of the first DACs that had an iPhone connector on it, and I was trying it out. It did sound good, but it was also hooked to some legendary-in-audiophile-circles amps and speakers. People were coming in the room, and commenting how amazing the amps sounded, and asked what the source was, and were very surprised when I told them they were 128k AAC files.

My personal opinion, based on A/B comparisons with a high-quality tuner from 1990, an NAD 4300, which has been re-capped, and the Sangean HDT-1X tuner is that the 4300 has a punchier sound with better stereo separation than the HD reception on the Sangean.

I think you need to take into account that most stations process their analog audio differently from their digital audio.

That being said, I believe that HD radio now uses a variation on "parametric stereo" that was part of the AAC-HE spec, which effectively re-synthesizes the stereo separation based on rules, in the same way it re-synthesizes the over 10khz content (spectral band replication or whatever it's called now).

There may be more noise on the NAD but there are no digital artifacts that are added as a result of HD encoding and decoding.

Also the HD radio CODECs aren't as good as AAC because they had to invent their own (for some marketing/licensing reason).

(Sorry if we're getting off-topic)

 

[rustyhodge]

I also wonder if any major FM radio broadcasters will in the future turn off their FM HD signals as a way to save money. They've made cutbacks in every other department; I wonder if this one is next?

If the HD signal doesn't have the reach of the analog signal, then possibly. But I think there are a lot of stations that extend their usable coverage area with digital's substantially less noisy signal at the edges.

What do you have to pay Xperi annually to transmit HD Radio? I've heard anecdotal reports of stations dropping it because of that cost.

 

[Kelly A]

I also wonder if any major FM radio broadcasters will in the future turn off their FM HD signals as a way to save money.

How would turning off HD carriers save any money? The investment is already made and a sunk cost.

They've made cutbacks in every other department; I wonder if this one is next?

Maybe savings having to pay someone to program music on additional HD2-5 channels, but there are no savings from 'turning off' HD-1.

 

[Brian Bowers]

How would turning off HD carriers save any money?

Are there no annual or monthly fees paid to DTS, or was it a one time fee? It's been a while, and I've forgotten.

 

[Kelly A]

Are there no annual or monthly fees paid to DTS, or was it a one time fee? It's been a while, and I've forgotten.

There is a one time larger fee, than small renewal fees along the way. Once you get past the initial investment, any other fees amount to accounting rounding errors in scope.

 

[Brian Bowers]

Once you get past the initial investment, any other fees amount to accounting rounding errors in scope.

I guess that's what I was getting at (however miniscule they may be). Corporate's been cutting wherever they can. I wonder if HD is immune. Maybe it is now, but who knows when and if the slashing will ever stop in radio.

 

[PTBoardOp94]

There are royalties to Xperi for using HD multicast channels ($1000/year last time I knew, but that price may not be current). That fee does not apply to the HD1 simulcast. That may be what Brian was thinking about.

 

[Kelly A]

I guess that's what I was getting at (however miniscule they may be). Corporate's been cutting wherever they can. I wonder if HD is immune. Maybe it is now, but who knows when and if the slashing will ever stop in radio.

Companies always get their cost reduction bang for the buck in FTE's. That's because full time employees come with 29-30% of benefits on top of salaries. The Xprei fees are also based on market size, so it's not like smaller markets would save much by eliminating HD. The problem is; much of the cost savings since 2019 have already been realized. Groups have carved down positions pretty close to the bone, and part timers and interns are pressed into temporary service so less annual cuts are necessary.

 

[Brian Bowers]

so less annual cuts are necessary.

Ha! I've heard that story before. I won't even be surprised when radio station employees are being asked to help out and bring in their own toilet paper.

pressed into temporary service

Temporary?

 

[Kelly A]

Ha! I've heard that story before. I won't even be surprised when radio station employees are being asked to help out and bring in their own toilet paper.

Sarcasm of course.

Temporary?

Sure. Part timers used for things like promotion are usually dismissed when the weather gets bad or the Holidays and over. Interns are limited how long they can remain as interns depending on state laws and the agreement with schools. Many states now require interns be paid at least minimum wage.

 

[TomásEstefan]

When was this published, 1997? Come to find out, HD radio interference for modern receivers never was a thing.
Sure, you use some capacitance sliderule tuner from the 60's might hear the sidebands, but that's likely the time one needs to evaluate the vintage of their hardware, especially when .001% of the radio listening public might suffer an issue.

One might ask then why is it that the night time reception of KIEB 1150 in some suburban locations in the Los Angeles area is significantly damaged by the digital skywave side bands of KSL 1160, no matter what type of radio is used? Same issue in portions of San Diego suburbs when listening to 1170 KCBQ.

 

[fybush]

One might ask then why is it that the night time reception of KIEB 1150 in some suburban locations in the Los Angeles area is significantly damaged by the digital skywave side bands of KSL 1160, no matter what type of radio is used? Same issue in portions of San Diego suburbs when listening to 1170 KCBQ.

Because this whole conversation has been about FM, not AM. The problems with the MA-1 "hybrid" AM system are well known and undisputed - and irrelevant to the FM discussion here.

 

[davideduardo]

Ha! I've heard that story before. I won't even be surprised when radio station employees are being asked to help out and bring in their own toilet paper.

The way I wormed worked my way into my first job in radio was by either bringing toilet paper to the studio bathroom or taking the employee collection and going to the market to buy a package of TP. Stations: WJMO/WCUY in Cleveland and cheap owner was Richard Eaton's United Broadcasting.

That was 64 years ago.

 

[Brian Bowers]

The way I wormed worked my way into my first job in radio was by either bringing toilet paper to the studio bathroom or taking the employee collection and going to the market to buy a package of TP.

Interesting story (Personally, I started out answering request lines for a few DJ's on the weekends during my high school years)! OK, but at that time you saw a *future* in radio, I'm sure. I would question anyone who did that today, trying to worm their way in (I'm kind of snickering as I write this).

Temporary?

Sure.

Oops. Sarcasm again on my part.

 

[Kelly A]

Let's put this discussion into perspective: When FM IBOC/HD radio was introduced over twenty (20) years ago there was this hue and cry from some engineering folks who claimed there would be all sorts of adjacent and co-channel noise and interference. From the opinions who matter, that's actual consumers, it was never a thing. That was true for purely analog listeners or those who had HD-capable tuners. Sure, there were other teething issues like analog vs. audio digital delay, refining things like importers and exporters, and moving to single transmitters from original high-level combining, but that's all in the past.
This whole radio nerd 'see I found a problem with HD Radio' is not only about twenty-five years too late, but none of the concern is anything new or consequential.

 

[TomásEstefan]

Because this whole conversation has been about FM, not AM. The problems with the MA-1 "hybrid" AM system are well known and undisputed - and irrelevant to the FM discussion here.

Oops ! Didn't realize the actual topic was FM

 

[TomásEstefan]

Let's put this discussion into perspective: When FM IBOC/HD radio was introduced over twenty (20) years ago there was this hue and cry from some engineering folks who claimed there would be all sorts of adjacent and co-channel noise and interference. From the opinions who matter, that's actual consumers, it was never a thing. That was true for purely analog listeners or those who had HD-capable tuners. Sure, there were other teething issues like analog vs. audio digital delay, refining things like importers and exporters, and moving to single transmitters from original high-level combining, but that's all in the past.
This whole radio nerd 'see I found a problem with HD Radio' is not only about twenty-five years too late, but none of the concern is anything new or consequential.

I will say that for DXers the adjacent channel problem is catastrophic, but for typical consumers, they wouldn't know what we are talking about!

 

[Kelly A]

I will say that for DXers the adjacent channel problem is catastrophic, but for typical consumers, they wouldn't know what we are talking about!

Exactly, and DX'ers mean nothing to the broadcast business because they spend zero money at sponsored businesses, nor are likely to donate to public radio in the process of DX-ing. I get it, it's a hobby one can do in their basement, but regarding any contribution to the signals they collect? DX'ers are by definition; parasites.