HD Radio

[PTBoardOp93]

If HD radio sounds better than conventional FM, there's no reason at all to use .wav files in station libraries. They ought to just compress 'em down to 128kbit/s AAC files and call it a day. After all, that's what HD listeners are hearing and if regular FM sounds worse...

Correct. When I got in the biz, radio played compressed tracks on the air just fine. If it wasn't played directly from a CD, it was compressed. Spots, music, imaging. All of it.

Back then it was largely MP2. All Westwood One, Premiere, and ABC Radio syndicated programs were delivered in MP2. The syndicator could select mono/stereo and the bit rate, from 32 kbps to 384 kbps.

We also played music off of minidisk.

 

[AMRadioGuy]

Correct. When I got in the biz, radio played compressed tracks on the air just fine. If it wasn't played directly from a CD, it was compressed. Spots, music, imaging. All of it.

Back then it was largely MP2. All Westwood One, Premiere, and ABC Radio syndicated programs were delivered in MP2. The syndicator could select mono/stereo and the bit rate, from 32 kbps to 384 kbps.

We also played music off of minidisk.

So... I'd beg to differ here for sure. When we went from using Barix Boxes to Bridge IT units at the stations I work for, the difference was noticeable - even on AM. And when we upped the bitrate on the Bridge ITs, again this was clearly audible on the air. As I went through and upgraded the music library on one of our AMs, being meticulous about source material, it's amazing how much better it sounded!

One of the stations I work for (FM) has a lot of heavily compressed tracks in their library. They sound... dreadful... on the air.

I set up the processing for the other AM I did a bunch of work on, and also set up the processing for its FM translator. The owner wanted to know why on earth the translator sounded so much better than the full power FM with a much nicer processor. Two words: source material. That AM & translator had all high-quality source material (it was oldies, so mono 45 mixes wherever appropriate, always good bitrate and good sounding sources) in the library and it showed when it was on the air.

Again, most people don't necessarily notice this - sure! Just as most people don't notice bad sounding processing, either. But just because they don't notice it consciously doesn't mean it doesn't matter...

 

[Wimmmex]

You've called my bluff - I don't own an HD radio...

You got it right @Kelly A !! ha-ha!

 

[AMRadioGuy]

You got it right @Kelly A !! ha-ha!

Kinda... I don't own one because my daily driver is a '66 Chevy Corvair with an AM/FM 8-track tape deck and the family car I drive through the PA winters is a little too old to have an HD radio. As I said in my post, my mother's car does have one and I've spent considerable time listening to it, along with in many other friends cars I've been in...

 

[Kelly A]

Kinda... I don't own one because my daily driver is a '66 Chevy Corvair with an AM/FM 8-track tape deck and the family car I drive through the PA winters is a little too old to have an HD radio. As I said in my post, my mother's car does have one and I've spent considerable time listening to it, along with in many other friends cars I've been in...

So let me get this straight: You claim to be in your twenties (GenZ) but call yourself AMRadioGuy and drive a 66 Corvair? As David has pointed out, you're what's known as an 'outlier'.

 

[DaveBayArea]

Correct. When I got in the biz, radio played compressed tracks on the air just fine. If it wasn't played directly from a CD, it was compressed. Spots, music, imaging. All of it.

Back then it was largely MP2. All Westwood One, Premiere, and ABC Radio syndicated programs were delivered in MP2. The syndicator could select mono/stereo and the bit rate, from 32 kbps to 384 kbps.

We also played music off of minidisk.

Later on people began to understand the effects of cascaded compression. These algorithms are designed to throw away information they think the human ear can't hear. Two layers of compression will be more noticeable than one. Some, such as Internet streaming or HD, cannot be avoided. But you can easily encode your audio to lossless .flac for the source material. With digital storage as cheap as it is these days there's no reason not to.

Dave B.

 

[PTBoardOp93]

But you can easily encode your audio to lossless .flac for the source material. With digital storage as cheap as it is these days there's no reason not to.

Absolutely, that's the right thing to do in 2024.

When I started in the biz in the 90s, there was no streaming, no HD radio and nothing digital in the airchain after the playout computer and satellite receivers, so no risk of colliding algorithms.

 

[davideduardo]

So let me get this straight: You claim to be in your twenties (GenZ) but call yourself AMRadioGuy and drive a 66 Corvair? As David has pointed out, you're what's known as an 'outlier'.

To clarify, in professional research, a person with unusual preferences in any field or area is called an "outlier" is that is factual, not offensive.

And in radio, that means a person whose tastes and preferences are quite unique and can't ever be satisfied by 'one-to-many' broadcast radio.

 

[Kelly A]

To clarify, in professional research, a person with unusual preferences in any field or area is called an "outlier" is that is factual, not offensive.

And in radio, that means a person whose tastes and preferences are quite unique and can't ever be satisfied by 'one-to-many' broadcast radio.

I get that, and neither of us meant it to be offensive. You have to admit, that lifestyle of loving AM radio and driving a 66 Corvair is unusual for a 20-something in modern life. Nothing wrong with it, just unusual. Ergo: outlier as compared with the majority of 20-somethings, would still be an accurate term.

 

[Dr. Bob]

That might be so... but it's not all about frequency response and noise floor and stereo separation.

I'm sorry, but analog FM sounds superior to me hands down. The reality is that the codec HD radio uses is... not great at all. It's outdated and very, very lossy.

Low bitrate mp3 files might have more stereo separation, frequency response, etc. than a decent cassette deck, but I'm taking the cassette every. single. time. At least it won't suffer from swishy drum syndrome.

Lets take a look at some specs and compare:

Lossy Compression: And this is where the wheels really come off for HD radio. I mentioned bitrate upstream. 128kbit/s is low. Really low. The compression standard is (as I understand it) similar to AAC. 128kbit/s is going to leave behind a lot of artifacts. Things like snare drums start sounding absolutely awful - swirly-like, reverb trails end up distorted, and all the stereo separation in the world doesn't matter a lot if it ends up distorted. From what I understand, a distorted stereo soundstage is indeed common at 128kbit/s.

If HD radio sounds better than conventional FM, there's no reason at all to use .wav files in station libraries. They ought to just compress 'em down to 128kbit/s AAC files and call it a day. After all, that's what HD listeners are hearing and if regular FM sounds worse...

Sure, analog FM has some issues too - things like pre/deemphasis can cause problems. But the reality is those problems are just not as awful sounding as the artifacts left behind by digital compression. Sometimes it's not just about specs - they don't always paint an accurate picture. Multipath distortion is also an issue with FM. But I don't think there's a lot of debate that analog distortion is more pleasing to the ear than digital distortion...

Oh, and of course, none of this debate even matters if the STL is a lossy piece of crap... or the station uses lossy files on-air like one of the stations in my area does.

And, of course, the other reality is that most people today are just so used to listening to audio that is digitally compressed that they think that Sirius XM sounds good. I mostly exist in an analog world, so that digital compression stands out like a sore thumb to me. It is not pleasing at all.

You kind of eluded to the issue with your discussion of lossy files. You can’t judge what a codec sounds like by running previously encoded audio through it. Ideally, if you feed the HD codec with non-data reduced audio, it will sound reasonably close to the source to most (but maybe not to you). This was all addressed during the peliminary HD testing as well as after. Here is a study by NPR about the HD codec verses bit rate:

https://modeltheory.org/papers/ssk/ssk2006hd-codec.pdf

Notice that with audio straight from the source CD the participants gave less than a perfect score. The broadcaster decides what bit rate to allocate to each subchannel, including those for data. My experience aligns closely to the NPR study, for those channels at 48 kbps and above HD fed non-data reduced audio HD sounds very close to the source material. Lower data rate channels less so and I have heard 24 kbps channels fed with previously encoded audio that sounded horrible. Under the conditions of at least 48 kbps bit rate, unencoded audio and with moderate audio processing, to my ears, HD sounds better than analog even if the analog is not experiencing multipath. Modern FM broadcast processors do a great job of increasing the loudness but as a side effect they smash the high end due to the 75 uS pre-emphasis curve. You can’t get away from physics - as Bob Orban so eloquently put it, “loudness, brightness, distortion - pick any two.” If you like smashed and/or dull high end audio, that’s your preference but studies show that a majority of listeners believe that well executed HD audio sounds close to the (non-data reduced) source.

 

[fybush]

And the key point, for the purposes of interesting discussion here on these boards, is that it's fine to be an outlier - we are all outliers here to some extent! - as long as you can put it in perspective and understand why the "average listener" isn't going to hear what we hear.

There's a lot of very bad HD audio out there in the real world - lossy source material, processing that isn't carefully set up, early generations of importers and exporters that really need to be updated.

None of those things make HD Radio "bad." They're just bad implementation of the technology.

I'm an outlier, too. I've been all over the country listening fairly carefully to thousands of FM stations in hundreds of markets over the last few years. And here's my conclusion: when it's done well, with careful attention to source material and processing and latest-generation encoding, HD FM fixes a lot of the problems with analog FM. I have lost count of how many times I've been in a hotel room trying to aircheck a format that depends on a low noise floor, especially classical or public radio talk, and finding the difference between a noisy multipath analog signal and solid HD makes all the difference between listenable and not.

Listeners don't need to know HD exists to benefit from it. If it's just "there" in the car they own - and right now that's about a one in three chance across the universe of hundreds of millions of vehicles on the road - they get a cleaner signal with less "static" and more stability as they drive around rough terrain.

I wouldn't build a new commercial FM facility without HD. I wish the costs of an HD build would come down more, so that it's less of an obstacle for smaller operators in the noncommercial world.

You'll notice I've said nothing about bitrates or dividing up subchannels, and there's a good reason for that: the compression algorithms in newer equipment have gotten so much better in the last few years. We're not broadcasting to audiophiles in perfectly quiet rooms. We're reaching real world listeners in noisy cars. They're accustomed to bit-reduced audio, for the most part. What they really don't like is "static," which for the non-expert listener is what we'd call multipath, picket-fencing and all the other problems with analog FM that HD mostly fixes when it's done right.

 

[kfbkfb]

What's the trend line for HD radio broadcasts (excluding usage to feed an FM translator), are more FM (or AM) radio stations adding HD broadcasting capability, holding steady or declining (slowly or dramatically)?

I have the Sony XDR-S3HD table radio (the only radio I've owned that isn't instant on, it has to initialize for a few seconds), I used it a lot to listen to Radio Disney 1190 AM in HD and now occasionally to FM HD subchannels.


Kirk Bayne

​

 

[PTBoardOp93]

What's the trend line for HD radio broadcasts (excluding usage to feed an FM translator), are more FM (or AM) radio stations adding HD broadcasting capability, holding steady or declining (slowly or dramatically)?

Audacy dropped a few HD subchannels last year as they struggled to find more cost saving measures. Other than that, it's roughly flat.

 

[fybush]

Largely stable, Kirk. FM HD is nearly universal among larger commercial and non-commercial players in large and most medium markets. There's little room for growth in that universe, and little to no reason for stations to drop HD once they're equipped with it.

It's still rare among small stations and in small markets, except where subs are being used to feed translators, and given the costs involved, it's going to stay rare for those stations.

I don't have the exact numbers at my fingertips, but it's probably about a quarter of all FM stations that have HD, a number that's neither declining nor likely to grow very fast.

There are always exceptions: I am adding HD next month to an independently-owned commercial station in my market that's operated without it for many years and is still #1 in the market even in all-analog. The owner is careful with his money - but it's also past time to replace an elderly transmitter, and I helped persuade him that if he's buying new, he may as well have a fully equipped modern signal for the 2020s.

 

[Mediafrog+]

I have the Sony XDR-S3HD table radio (the only radio I've owned that isn't instant on, it has to initialize for a few seconds)

I’ve had radios in the past that weren’t “instant on” due to a process known as “letting the vacuum tubes warm up”.🤣

 

[kfbkfb]

Hence my phrasing - my parents owned a Zenith tube FM/AM radio (I sometimes listened to WDAF FM 102.1 on it) and of course they owned tube TV sets...and now back to the regularly scheduled thread...


Kirk Bayne

 

[cc333]

I’ve had radios in the past that weren’t “instant on” due to a process known as “letting the vacuum tubes warm up”.🤣

Not radio related per se, I have an Ampex reel to reel tape recorder which uses tubes, and I need to let it warm up for a minute (the motor also takes a bit to come up to full speed, but that's a lubrication issue I need to figure out).

...and now back to the regularly scheduled thread...

...already in progress...

c

 

[BruceB]

Largely stable, Kirk. FM HD is nearly universal among larger commercial and non-commercial players in large and most medium markets. There's little room for growth in that universe, and little to no reason for stations to drop HD once they're equipped with it.

It's still rare among small stations and in small markets, except where subs are being used to feed translators, and given the costs involved, it's going to stay rare for those stations.

I don't have the exact numbers at my fingertips, but it's probably about a quarter of all FM stations that have HD, a number that's neither declining nor likely to grow very fast.

There are always exceptions: I am adding HD next month to an independently-owned commercial station in my market that's operated without it for many years and is still #1 in the market even in all-analog. The owner is careful with his money - but it's also past time to replace an elderly transmitter, and I helped persuade him that if he's buying new, he may as well have a fully equipped modern signal for the 2020s.

We have an Alpha Media group in Dayton
and no HD on any of them. I hear they are kind of frugal.

 

[Mark Roberts]

Hence my phrasing - my parents owned a Zenith tube FM/AM radio (I sometimes listened to WDAF FM 102.1 on it) and of course they owned tube TV sets...and now back to the regularly scheduled thread...

So...what happened to the radio the day in 1974 when WDAF-FM became KYYS?

 

[AMRadioGuy]

So let me get this straight: You claim to be in your twenties (GenZ) but call yourself AMRadioGuy and drive a 66 Corvair? As David has pointed out, you're what's known as an 'outlier'.

Oh no question about it. I am very much an outlier!

Then again - in a radio context... pretty much everyone on this board is an outlier. Your average Joe responding to a radio survey is not going online to a radio forum to discuss the medium.