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Expert thoughts on HD

F

FM_Listener

Curious what you experts think about HD radio (on the FM band).

My personal observations are that it's nice to have the extra logical channels sometimes, but the audio quality even on the primary channel is lousy. Some people seem to think it sounds better, but I think they just perceive a lack of static and distortion (caused by multi-path) as better, and they don't realize the severe lack of dynamic range and high frequencies.

This paper seems to show that even if the analog signal were turned off the max bit rate is still 98.4 kbps (yuck):

https://hdradio.com/sites/default/files/waveforms_fm.pdf

I've also read that some true audiophiles in Europe are not too happy with DAB because broadcasters have chosen to give up fidelity in favor of more logical channels. Sirius XM is the extreme example of this poor trade off.

Thanks for any opinions.
 
The whole HD-1 thing does accomplish a couple things:

1. A better signal to noise ratio than analog FM.
2. Wider frequency response and stereo separation than analog FM.

I submit much of the criticism of the HD-1 audio quality (depending on the station and format) is due to the stations audio processing of the HD-1 stream in an effort to closely match the analog audio, instead of the other way around. That way when the receiver switches between the digital and analog audio, the difference isn't as noticeable. Stations effectively 'grunge-up' their HD-1 audio so is sounds close to their overly processed analog audio.

The exception seems to be with classical music stations, where the audio quality accuracy and dynamic range is more important than the analog loudness wars, left over from the 1970's.
 
HD is great for OTA television, not so much with radio. IMO, HD1 audio quality is sub-par at best most HD2, HD3 subchannels are barely listenable. Better off streaming from your phone into the car stereo or headphones.

The only positive to HD radio is the FCC allowing HD2 programming on FM translators. Some of those stations have good formats.
 
Big D said:
HD is great for OTA television, not so much with radio. IMO, HD1 audio quality is sub-par at best most HD2, HD3 subchannels are barely listenable. Better off streaming from your phone into the car stereo or headphones.
.
Click to expand...

The quality of each HD channel depends on the percentage of the total HD bandwidth given to it.
 
I did my college thesis on HD radio vs the European standard (DAB/DAB+ digital radio). This was back in 2007. But at the time there were many studies relating to certain levels of interference an HD station with side channels would cause adjacent freq. This was especially an issue with high power stations vs LPFM and markets that have basically no space in between stations. Honestly, I listen to HD, but I didn't expect it to last this long.
 
polenta3 said:
But at the time there were many studies relating to certain levels of interference an HD station with side channels would cause adjacent freq. This was especially an issue with high power stations vs LPFM and markets that have basically no space in between stations. Honestly, I listen to HD, but I didn't expect it to last this long.
Click to expand...

Because of the FCC's decades old adjacency rules, this is literally not a problem anywhere. Unless you're a pirate trying to squeeze yourself into the band.
 
Kelly A said:
The whole HD-1 thing does accomplish a couple things:

1. A better signal to noise ratio than analog FM.
2. Wider frequency response and stereo separation than analog FM.

I submit much of the criticism of the HD-1 audio quality (depending on the station and format) is due to the stations audio processing of the HD-1 stream in an effort to closely match the analog audio, instead of the other way around. That way when the receiver switches between the digital and analog audio, the difference isn't as noticeable. Stations effectively 'grunge-up' their HD-1 audio so is sounds close to their overly processed analog audio.

The exception seems to be with classical music stations, where the audio quality accuracy and dynamic range is more important than the analog loudness wars, left over from the 1970's.
Click to expand...

Agreed, Kelly A

As an LPFM. Our car listeners don't have to drive too many miles to reach the edge of our service contour. Matching HD1 quality to our analog service was key to making the blending more seamless.

I would add that HD Radio sometimes gets a bad rep because some station might still be using poorly encoded mp3 files as a source. Since we're a grade-school station, you can imagine the varied quality of the original audio programs submitted to us; some done in our studios and some done at home on a little iPad or smartphone.

Overall, I find HD Radio an excellent addition to our LPFM service.
 
polenta3 said:
I did my college thesis on HD radio vs the European standard (DAB/DAB+ digital radio). This was back in 2007. But at the time there were many studies relating to certain levels of interference an HD station with side channels would cause adjacent freq. This was especially an issue with high power stations vs LPFM and markets that have basically no space in between stations. Honestly, I listen to HD, but I didn't expect it to last this long.
Click to expand...

Mexico just reduced its spacing requirements; they are now similar to what they are in the rest of Latin America and much of the world. And Mexico, particularly the large markets, has a rapidly growing number of HD operations. Even with stations just 400 kHz apart, they don't interfere.
 
I wish the FCC would relax the adjacent protection. I was complaining about this in the Denver/Boulder forum. They are putting translators on channels that wipe out (distant, but listenable if you have the right equipment) co-channel stations, while a perfectly open channel sits there protected because of adjacency.

With my home analog tuner there is one somewhat distant station I listen to that has a very strong station next door. With the IF filter setting on wide I get a bit of noise, but on narrow it's fine with hardly any loss of fidelity. I think almost all car tuners have all kinds of automatic things built in to minimize issues.

And I really don't get the scenario of protecting a high power station from an adjacent low power translator.
 
Ralph Martin said:
I would add that HD Radio sometimes gets a bad rep because some station might still be using poorly encoded mp3 files as a source.
Click to expand...

You're absolutely right Ralph. MP3 files sound bad because of the 'dueling algorythms' between the audio file and the HD Radio Encoder/Exporter. Stations that run HD radio, do themselves an incredible disservice by using MP3's on the air. How ironic that a LPFM understands that simple fact, yet commercial stations don't always.

Ralph Martin said:
Overall, I find HD Radio an excellent addition to our LPFM service.
Click to expand...

And I applaud you, and your school's efforts in making the commitment to run HD radio on your LPFM. As you've seen, having done so really is a technical advantage, provided one can afford it going in. As you've probably noticed; many LPFM's around the country have failed because they've either been started with good intentions but held unrealistic expectations. That, and many failed stations have been under-capitalized.
 
Kelly A said:
As you've probably noticed; many LPFM's around the country have failed because they've either been started with good intentions but held unrealistic expectations. That, and many failed stations have been under-capitalized.
Click to expand...

I know that there are several anecdotes of failed or failing LPFM's. The way I look at it; unlike most other FM broadcast services, LPFM's vetting process continues long after the granting of the construction permit. The fact that many didn't honestly know what they were getting into is understandable in a service designed to allow new players. Those who've decided to move on learned something. I encourage them not to give up their valuable sense of community service in whatever they choose to do next!

I've been fortunate to correspond with a number of LPFM's who have succeeded against enormous odds. They've become an excellent source of pride and connection in their communities. Listen to KDRT-LP in Davis, CA for an hour; it just "feels" like Davis. Listen to KFOK-LP in Georgetown, and you feel like you've just spent a bit of time in their little mountain town. What a compliment LPFM is to the larger commercial and non-com operations!

Will LPFM's adopt HD Radio?? It worked for us, and now the cost has come down around 50% from when we started. Hybrid digital is an interim technology by design. Let's see what happens.
 
Last edited:
Ralph Martin said:
I know that there are several anecdotes of failed or failing LPFM's. The way I look at it; unlike most other FM broadcast services, LPFM's vetting process continues long after the granting of the construction permit. The fact that many didn't honestly know what they were getting into is understandable in a service designed to allow new players. Those who've decided to move on learned something. I encourage them not to give up their valuable sense of community service in whatever they choose to do next!

I've been fortunate to correspond with a number of LPFM's who have succeeded against enormous odds. They've become an excellent source of pride and connection in their communities. Listen to KDRT-LP in Davis, CA for an hour; it just "feels" like Davis. Listen to KFOK-LP in Georgetown, and you feel like you've just spent a bit of time in their little mountain town. What a compliment LPFM is to the larger commercial and non-com operations!

Will LPFM's adopt HD Radio?? It worked for us, and now the cost has come down around 50% from when we started. Hybrid digital is an interim technology by design. Let's see what happens.
Click to expand...

Here in central NH we now have WNHN-LP (94.7) in Concord.....the format is Jazz/Blues......and is EXTREMELY popular around the Capital area (their coverage is only about a 5-6 mile radius around Concord -- they have WHOM (Mt. Washington) blasting away at 94.9, and WQNH-LP in Deerfield -- also on 94.7!!
Originally WNHN-LP was WCNH-LP; it played classical music....The owner sold the station to Concord after he got a CP for a new station in nearby Bow for 91.5...he moved the call sign over and now carries classical music via the HD2 service of WEVO (89.1)/NH Public Radio.
Together the 2 LPFMs fill their respective niches admirably.....!!
 
FM_Listener said:
I wish the FCC would relax the adjacent protection. I was complaining about this in the Denver/Boulder forum. They are putting translators on channels that wipe out (distant, but listenable if you have the right equipment) co-channel stations, while a perfectly open channel sits there protected because of adjacency.

With my home analog tuner there is one somewhat distant station I listen to that has a very strong station next door. With the IF filter setting on wide I get a bit of noise, but on narrow it's fine with hardly any loss of fidelity. I think almost all car tuners have all kinds of automatic things built in to minimize issues.

And I really don't get the scenario of protecting a high power station from an adjacent low power translator.
Click to expand...

There have been many fights it Chicagoland in recent years due to this. Mostly translators. One was in the loop and not more than 18 watts, yet it was causing major interference to two suburban stations; one in NW Indiana and one in the NW Suburbs.
 
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