Is AM-HD really FM Quality?

[ajc_trw]

San Francisco is in a unique situation in answering this question. KCBS is broadcasting IBOC on AM while symalcasting on FM. Anyone with an HD radio can switch between AM-HD and FM and tell us if they sound the same.

I thought of asking in HD Radio but I thought the trendy folks in SF would have an HD radio and wouldn't mind giving us a review of the latest in technology.

So San Francisco, inquiring mind want to know. Please! ;D

 

[LKellerIII]

Perhaps this is a sign of how far AM has fallen. I've had an HD car radio for over a year now, and listen to the HD2 channels on FM often, but it's never occurred to me to check the AM HD band.

I'll check, and get back to you...

 

[RadioStarOne]

No, but it is in stereo though.

 

[LKellerIII]

San Francisco is in a unique situation in answering this question. KCBS is broadcasting IBOC on AM while symalcasting on FM. Anyone with an HD radio can switch between AM-HD and FM and tell us if they sound the same.

I thought of asking in HD Radio but I thought the trendy folks in SF would have an HD radio and wouldn't mind giving us a review of the latest in technology.

So San Francisco, inquiring mind want to know. Please! ;D

Short answer - NO - not FM quality. As Radio Star pointed out - it seems to be in stereo, though it has a somewhat echo-like quality,..not so much real stereo with true separation, but a slight delay between the right channel and the left. I may be wrong, but that's the way it sounded to me.

Sorry, but I'm uneducated about sound from a scientific perspective, and I'm not up on the terminology, so I can only describe it in simple English.

I listened first to 740 for about 30 seconds, then switched (via the band-button) to 106.9, then repeated the exercise 3 times. To my ears, the FM signal was still clearly superior for clarity, as well as highs and lows.

However, when I switched between 740 and my other AM pre-sets (560, 680, 810, 910, 960), 740 sounded better than the other AMs to me.

By the way - you don't have to be "trendy" to have an HD radio. My older car needed a new CD player. The AM/3 band FM/CD/MP3-ready unit was only $20 more with HD than without. I considered it a real bargain since I can get about 15 new commercial free FM HD2 music streams now. It doesn't have the variety that XM/Sirius would provide, but there's no monthly fee, either.

 

[radioman148]

San Francisco is in a unique situation in answering this question. KCBS is broadcasting IBOC on AM while symalcasting on FM. Anyone with an HD radio can switch between AM-HD and FM and tell us if they sound the same.

I thought of asking in HD Radio but I thought the trendy folks in SF would have an HD radio and wouldn't mind giving us a review of the latest in technology.

So San Francisco, inquiring mind want to know. Please! ;D

The problem with AM HD for me is that you can't get the AM signal in HD very far--20 miles or so in my case.

 

[pqgeorge]

San Francisco is in a unique situation in answering this question. KCBS is broadcasting IBOC on AM while symalcasting on FM. Anyone with an HD radio can switch between AM-HD and FM and tell us if they sound the same.

I thought of asking in HD Radio but I thought the trendy folks in SF would have an HD radio and wouldn't mind giving us a review of the latest in technology.

So San Francisco, inquiring mind want to know. Please! ;D

The problem with AM HD for me is that you can't get the AM signal in HD very far--20 miles or so in my case.

Ditto here. The AM-HD (IMHO) decoded signal sounds "synthetic" in terms of the high-end frequency response. It sounds like somebody is trying to get the extra high frequency response, but is hitting a brick wall. To compensate, it sounds like the highs were re-introduced after the fact. And yes, the coverage area on an AM-HD station is very limited. I live about 25 miles from the WBZ (1030/Boston) transmitter site in Hull, MA, in their main lobe. Their signal always drops in and out of sync with the HD carrier. Even with a longwire antenna (I'm a ham operator), their signal has tendency to fluctuate in and out of decoding. Very irritating. WMKI (1260) also an HD station just blinks the HD display but never decodes.

AM-HD, IMHO, is definitely not "ready for prime time". I've always equated AM-HD in trying to make "a silk purse out of sow's ear". It doesn't cut it.

I know that Tom Ray (that great WOR/New York engineer) swears by HD Radio. His station (WOR/710, New York City) was the first full-time HD-AM station. In the past, we've had a few a couple of "spirited" conversations about HD radio (pro and con), both on voice and on e-mail. Obviously, I was in the "opposing" point of view. And you know Tom's POV. But, if anyone could make HD-AM work, Tom's the man.

Personally though, I don't think HD-AM is long for this world.

 

[Michael Rivers Kramer]

San Francisco is in a unique situation in answering this question. KCBS is broadcasting IBOC on AM while symalcasting on FM. Anyone with an HD radio can switch between AM-HD and FM and tell us if they sound the same.

I thought of asking in HD Radio but I thought the trendy folks in SF would have an HD radio and wouldn't mind giving us a review of the latest in technology.

So San Francisco, inquiring mind want to know. Please! ;D

The problem with AM HD for me is that you can't get the AM signal in HD very far--20 miles or so in my case.

Ditto here. The AM-HD (IMHO) decoded signal sounds "synthetic" in terms of the high-end frequency response. It sounds like somebody is trying to get the extra high frequency response, but is hitting a brick wall. To compensate, it sounds like the highs were re-introduced after the fact. And yes, the coverage area on an AM-HD station is very limited. I live about 25 miles from the WBZ (1030/Boston) transmitter site in Hull, MA, in their main lobe. Their signal always drops in and out of sync with the HD carrier. Even with a longwire antenna (I'm a ham operator), their signal has tendency to fluctuate in and out of decoding. Very irritating. WMKI (1260) also an HD station just blinks the HD display but never decodes.

AM-HD, IMHO, is definitely not "ready for prime time". I've always equated AM-HD in trying to make "a silk purse out of sow's ear". It doesn't cut it.

I know that Tom Ray (that great WOR/New York engineer) swears by HD Radio. His station (WOR/710, New York City) was the first full-time HD-AM station. In the past, we've had a few a couple of "spirited" conversations about HD radio (pro and con), both on voice and on e-mail. Obviously, I was in the "opposing" point of view. And you know Tom's POV. But, if anyone could make HD-AM work, Tom's the man.

Personally though, I don't think HD-AM is long for this world.

Then again even with the limited range of the decoded signal...The added noise with IBOC extends a lot farther.

 

[radioman148]

San Francisco is in a unique situation in answering this question. KCBS is broadcasting IBOC on AM while symalcasting on FM. Anyone with an HD radio can switch between AM-HD and FM and tell us if they sound the same.

I thought of asking in HD Radio but I thought the trendy folks in SF would have an HD radio and wouldn't mind giving us a review of the latest in technology.

So San Francisco, inquiring mind want to know. Please! ;D

The problem with AM HD for me is that you can't get the AM signal in HD very far--20 miles or so in my case.

Ditto here. The AM-HD (IMHO) decoded signal sounds "synthetic" in terms of the high-end frequency response. It sounds like somebody is trying to get the extra high frequency response, but is hitting a brick wall. To compensate, it sounds like the highs were re-introduced after the fact. And yes, the coverage area on an AM-HD station is very limited. I live about 25 miles from the WBZ (1030/Boston) transmitter site in Hull, MA, in their main lobe. Their signal always drops in and out of sync with the HD carrier. Even with a longwire antenna (I'm a ham operator), their signal has tendency to fluctuate in and out of decoding. Very irritating. WMKI (1260) also an HD station just blinks the HD display but never decodes.

AM-HD, IMHO, is definitely not "ready for prime time". I've always equated AM-HD in trying to make "a silk purse out of sow's ear". It doesn't cut it.

I know that Tom Ray (that great WOR/New York engineer) swears by HD Radio. His station (WOR/710, New York City) was the first full-time HD-AM station. In the past, we've had a few a couple of "spirited" conversations about HD radio (pro and con), both on voice and on e-mail. Obviously, I was in the "opposing" point of view. And you know Tom's POV. But, if anyone could make HD-AM work, Tom's the man.

Personally though, I don't think HD-AM is long for this world.

Then again even with the limited range of the decoded signal...The added noise with IBOC extends a lot farther.

The noise it causes is not worth the small advantage it provides IMO.

 

[pqgeorge]

On the noise issue, I have to agree. In spite of the limited range for the decoded signal, AM-HD is a killer in terms of interference. Especially at night, the adjacent frequencies are bathed with IBOC splatter for hundreds of miles. The analog signal sounds no better than a "dial-up" POTS line. Some stations tweak their frequency response down to 4 kHz with the use of "brick wall" filtering in order to "protect" the IBOC subcarriers. The result, the analog sounds like crap.... plain and simple. I have my thoughts about FM-HD as well. But that will have to wait for another time.

In the real world, AM-HD will never sound like FM. It's like trying to put a square peg into a round hole.

 

[K6JHU]

I am not a believer in AM HD. I do listen to the HD-2 and HD-3 channels a lot. Where I have done a comparison test between AM and the same signal on HD-2, the HD-2 signal has been consistently superior in terms of sound quality.

Having said that, where I am listening to AM HD, the big advantage is that you do not hear the AM interference generators (power lines in particular). The sound is rock steady. What I would like to do is find a station that still plays music on AM and is in HD to hear how that sounds. I have not had good luck.

 

[radioman148]

I am not a believer in AM HD. I do listen to the HD-2 and HD-3 channels a lot. Where I have done a comparison test between AM and the same signal on HD-2, the HD-2 signal has been consistently superior in terms of sound quality.

Having said that, where I am listening to AM HD, the big advantage is that you do not hear the AM interference generators (power lines in particular). The sound is rock steady. What I would like to do is find a station that still plays music on AM and is in HD to hear how that sounds. I have not had good luck.

I cannot find an AM-HD music station either in order to make that comparison.

 

[ajc_trw]

Thanks to all who answered. Like I said San Francisco is in a unique position to compare FM-Quality (AMHD) with FM (the real deal).

I guess if you want FM quality you need an FM station.

To IBOC:

 

[DanStrassberg]

In the real world, AM-HD will never sound like FM. It's like trying to put a square peg into a round hole.

In theory, AM HD ought to sound pretty much like FM HD on a station that is broadcasting HD-2 and HD-3 sub-channels. When broadcasting two sub-streams plus a main stream, most FMs will divvy up the 96 kbps HD bit rate into three 32 kbps streams. The AM bit rate is 32 kbps--period, exclusive of the small amount of bandwidth used for station ID and song titles on the digital display. So if AM HD sounds different from FM HD on a station that is running three streams, somebody ought to explain why.

 

[SFStatic]

AM HD sounds like FM to me on a Boston Acoustics Receptor. FM HD sounds great, but not quite CD quality, in my opinion.

 

[LKellerIII]

AM HD sounds like FM to me on a Boston Acoustics Receptor. FM HD sounds great, but not quite CD quality, in my opinion.

That could be part of the problem. My AM-HD listening experiment was on my car radio - a mid-priced JVC unit with high quality FM sound. But it's been my experience the last 20 years or so that AM bands on car stereos are low quality for sound and reception. I remember that 'back in the day,' those AM only car radios had superior sound, and got much better reception (with less static) than current car radios.

In the late 70s, I owned a 69 Mercury Cougar (a real boat) with an AM radio that would pull in distant low power stations like 990 KKIS in Concord like it was KGO or KCBS.

Of course, that means that even if AM HD has high quality sound, the public won't be drawn back to the AM iband if the sound is still sucks on the radios they already listen to.

 

[DaveBayArea]

To my ear, AM HD sounds significantly worse than FM. Both monitored on a home stereo with a Sony XDR-F1HD, a Yamaha amplifier, and JBL Studio Monitors. It sounds like a bad webcast. Even FM HD doesn't sound as good as a high-quality Webcast stream, IMHO.

Dave B.

 

[fybush]

In my travels, I've had the chance to listen to many of the AM HDs that are on the air around the country. Many sound atrocious - but I've heard just enough that don't sound that way to convince me that there is a black art to creating good-sounding AM HD. The secret, at least with talk content, is to gently roll off the high end starting around 8 kHz, allowing the codec to do a better job with the lower frequencies and avoiding the synthesized high end that's so annoying. Another factor that's hard to avoid is cascading codecs - if you have a talk host originating via ISDN from a remote studio, then another layer of compression from studio to network TOC, then another layer of compression from network TOC to uplink, and sometimes yet another layer of compression if the program is delayed broadcast at the local end, you're lucky if any semblance of the original audio makes it through the far end even before it hits the IBOC codec.

That said, I've heard local programming via AM HD that sounds far better than you'd ever expect with just 32kbps...but it's a rare thing, and it takes an engineer who's willing (and able) to spend the time to get it right - and a transmitter facility that can pass the signal cleanly, too. There's certainly much more bad HD audio out there than good, on both FM and AM...but it really depends more on the individual station/engineer than on the system as a whole.

(I have not heard the San Francisco HD AMs recently, so cannot comment on them specifically.)

 

[SFStatic]

Cascading codecs is a big problem for am talk. As one great engineer I know says, it makes the audio sound "crunchy" by the time you roll through all of them on a satellite delivered syndicated show.

 

[DaveBayArea]

I don't know why I didn't think of that before. Of course that makes perfect sense. Now if only an AM broadcaster around here would actually start with a lossless source & take some care with processing. I bet it WOULD sound good.

Dave B.

 

[radioman148]

My ears aren't anywhere near as good as they used to be but AM HD sounds about equal to FM to me.