AM HD Radio audio response: 4.4 kHz!?

[kevtronics]

According to the specs on Dual's web site ( http://www.dualav.com/ ), the AM HD Radio digital audio response for their two HD Radio car tuners, the XHD6420 and XHD6425, is 30 Hz to 4.4 kHz. They list the FM HD audio response as 30 Hz to 20 kHz.

Whatever happened to "near-FM quality" 15 kHz audio from AM HD? 4.4 kHz is worse than many analog AM radios -- although Dual manages to boast an analog AM response of only 240 Hz (!?) to 3 kHz on their HD tuners.

Best Buy has the XHD6420 on display, but of course the stores in my area don't set up any kind of antenna with AM reception for their car stereo rack, so I can't verify what it sounds like on AM, either in analog or digital.

 

[pbf1]

Dual is the Kraco of the new millenium.

Kenwood's AM HD is 30-15k.

AM HD was always hyped as FM quality (and FM as CD quality).

 

[Radioman100]

According to the specs on Dual's web site ( http://www.dualav.com/ ), the AM HD Radio digital audio response for their two HD Radio car tuners, the XHD6420 and XHD6425, is 30 Hz to 4.4 kHz. They list the FM HD audio response as 30 Hz to 20 kHz.

Whatever happened to "near-FM quality" 15 kHz audio from AM HD? 4.4 kHz is worse than many analog AM radios -- although Dual manages to boast an analog AM response of only 240 Hz (!?) to 3 kHz on their HD tuners.

Best Buy has the XHD6420 on display, but of course the stores in my area don't set up any kind of antenna with AM reception for their car stereo rack, so I can't verify what it sounds like on AM, either in analog or digital.

I'd guess that's a misprint. They would have to add circuitry to rolloff the output of the HD Radio circuitry in those radios to make that spec accurate, and I seriously doubt a company like Dual would add unnecessary components to the design.

 

[hipporadio]

This is HORRIBLE performance for a “new technology” AM tuner—even in “analog mode”... But, alas—it seems commonplace!

EVERY TIME I question a Consumer Electronics-type about the lack of AM quality—they respond: “It’s AM... And we’re designing the receiver to avoid the effects of resident noise and RF interference”. A correct analogy would be: The radio biz is “interfering with itself”—especially when AM IBOC enters the fray!

I was listening to a Sangean WR-2 that I purchased as a gift to my parents. It sits on an ole-fashioned “pie cabinet” in their eastern-Indiana kitchen. There are pre-sets assigned to local 1580—WIFE; 700—WLW and 1070—WIBC—which degrade themselves with IBOC... WIFE DOES NOT—it has a year-old rig and modern digital processing and SOUNDS GREAT! The Sangean receiver has a fine AM section [allegedly using the chips employed in C Crane’s signature AM radio]. Although it CANNOT be tuned in 1 kHz increments [to “brighten” AM listening]—its digital “center-tune” offers a very “musical” AM audio quality. 1580 WIFE approaches “FM quality” on this radio with their local signal in their kitchen. WLW—just a tad-below “local” is full of “HD hash”—NOISE NOT apparent before their decision to degrade themselves with IBOC... WIBC—once awesome in quality – sounds like crap and is near-UNLISTENABLE on this fine radio!

WHY in the “modern age” of AM radio—with its advantage of fine transmission equipment, would some [in the “corporate radio realm”] purposely-choose to DEGRADE themselves on decent AM receivers? LESS than A-TENTH of ONE-PERCENT receive a “swishy” IBOC HD digital signal; yet these stations choose to degrade themselves to the over-99-percent listing on ANALOG receivers... THIS MAKES NO SENSE!

 

[Radioman100]

This is HORRIBLE performance for a “new technology” AM tuner—even in “analog mode”... But, alas—it seems commonplace!

EVERY TIME I question a Consumer Electronics-type about the lack of AM quality—they respond: “It’s AM... And we’re designing the receiver to avoid the effects of resident noise and RF interference”. A correct analogy would be: The radio biz is “interfering with itself”—especially when AM IBOC enters the fray!

I was listening to a Sangean WR-2 that I purchased as a gift to my parents. It sits on an ole-fashioned “pie cabinet” in their eastern-Indiana kitchen. There are pre-sets assigned to local 1580—WIFE; 700—WLW and 1070—WIBC—which degrade themselves with IBOC... WIFE DOES NOT—it has a year-old rig and modern digital processing and SOUNDS GREAT! The Sangean receiver has a fine AM section [allegedly using the chips employed in C Crane’s signature AM radio]. Although it CANNOT be tuned in 1 kHz increments [to “brighten” AM listening]—its digital “center-tune” offers a very “musical” AM audio quality. 1580 WIFE approaches “FM quality” on this radio with their local signal in their kitchen. WLW—just a tad-below “local” is full of “HD hash”—NOISE NOT apparent before their decision to degrade themselves with IBOC... WIBC—once awesome in quality – sounds like crap and is near-UNLISTENABLE on this fine radio!

WHY in the “modern age” of AM radio—with its advantage of fine transmission equipment, would some [in the “corporate radio realm”] purposely-choose to DEGRADE themselves on decent AM receivers? LESS than A-TENTH of ONE-PERCENT receive a “swishy” IBOC HD digital signal; yet these stations choose to degrade themselves to the over-99-percent listing on ANALOG receivers... THIS MAKES NO SENSE!

Naah... It makes PERFECT sense Hippo!

Very few people own radios that will let you hear the hash. I can't hear hash at all in my 2006 model vehicle. In fact, I've never heard it in ANY vehicle.

Might I be able to hear it on my cheap clock radio? Maybe, but it sounds like crap anyway and with all the other interference out there, who knows?

On the other hand, hardly anyone makes a decent AM radio anymore and hardly anyone is likely to. Adding HD is the only way to get most manufacturers interested in making AM radios with decent audio performance.

It really doesn't matter either way though. You can stick a fork in AM. It's either dead or dying, and the talk stations that actually matter are slowly moving to FM, like WIBC.

 

[hipporadio]

Again, the HD Gang shines—with their mastery of “intelligence” and ARROGANCE! It’s ALL the fault of the fine Sangean WR-2... And not one’s coveted BA HD Receptor—discontinued due to poor sales, reviews, and company embarrassment! I need to find an urban zoo so I can bang my head and live-up to the profile of another of your “HD elite” on this board :

‘Glad you mentioned WIBC—a flawed flip that is TWENTY-YEARS past its prime... One managed by a company prone to knee-jerk reactions and on the defense from an OFFICAL stockholder REVOLT! There is a lot of “history” behind the assorted licensee’s use [and abuse] of Indy’s 93.1 FM frequency... Jim Duncan even called it: “A true radio enigma”—before Emmis bought-out his publication.

FACT: Indianapolis has outgrown the coverage afforded at pattern/power-switch by the 1070 AM frequency. Affluent and growing Hamilton County is OUTSIDE the coverage-confines of WIBC until 8:30 AM [courtesy of extended Daylight Savings Time] in early-November. This is actually a problem that has been TWENTY-YEARS in the making – and has NOTHING to do with the alleged AM demodulation capacity of a Sangean WR-2 OR HD RADIO for that matter!

Nice try... NO cigar

 

[Radioman100]

Again, the HD Gang shines—with their mastery of “intelligence” and ARROGANCE! It’s ALL the fault of the fine Sangean WR-2... And not one’s coveted BA HD Receptor—discontinued due to poor sales, reviews, and company embarrassment! I need to find an urban zoo so I can bang my head and live-up to the profile of another of your “HD elite” on this board :

Maybe so, your memory seems to be suffering. We already discussed the Receptor's status in another thread not even a day ago. It's going strong on BA's website and in their web store.

‘Glad you mentioned WIBC—a flawed flip that is TWENTY-YEARS past its prime... One managed by a company prone to knee-jerk reactions and on the defense from an OFFICAL stockholder REVOLT! There is a lot of “history” behind the assorted licensee’s use [and abuse] of Indy’s 93.1 FM frequency... Jim Duncan even called it: “A true radio enigma”—before Emmis bought-out his publication.

FACT: Indianapolis has outgrown the coverage afforded at pattern/power-switch by the 1070 AM frequency. Affluent and growing Hamilton County is OUTSIDE the coverage-confines of WIBC until 8:30 AM [courtesy of extended Daylight Savings Time] in early-November. This is actually a problem that has been TWENTY-YEARS in the making – and has NOTHING to do with the alleged AM demodulation capacity of a Sangean WR-2 OR HD RADIO for that matter!

Nice try... NO cigar

Guess again. Bonneville did the exact same thing (right down to the final formats) with KTAR Phoenix a while back, and KTAR-AM certainly wasn't signal challenged. This is a scenario we're going to see play out again and again. It's been happening in Canada for years.

 

[Savage]

Isn't the upper frequency response on AM-HD "replicated" (IBOC-speak for "faked" or, if you prefer, "electronically reprocessed to simulate actual audio") above 4.5 kHz WITHIN the receiver? This would explain the counterintuitive 4.4 kHz bandpass for the AM section.

This appears to be the source of many listeners' objections to IBOC-AM sound. The codec doesn't do a very good job of simulating the analog waveforms; it can't keep up, hence the "chorusing" or "metallic" effect many listeners find objectionable. Most stations using IBOC-AM that I've heard sound like a bad internet audio stream. Literally the only positive is the lower noise floor.

 

[4dude]

Sounds like crap.... Compressed,etc..

 

[rbrucecarter5]

Very few people own radios that will let you hear the hash. I can't hear hash at all in my 2006 model vehicle. In fact, I've never heard it in ANY vehicle.

I hear the hiss clearly on every one of my car radios. In fact, I hear it on the narrowest bandwidth radio I own at home - a GE Superadio 1. Every station, every time, no matter how carefully I tune.

 

[Mike Walker]

I've actually never heard a SuperRadio 1. (I've owned a couple of SuperRadio IIIs, as well as the Radio Shack clone). Was the SuperRadio 1 REALLY narrow? The SuperRadio III is quite wide (of course, everyone knows that). Now the old Panasonic RF2200, THAT thing was narrow (and unbelievably sensitive!)

 

[JohnnyElectron]

At least Leonard Kahn's AM CAM-D goes up to 7.5KHz REAL analog before the digital starts to be intertwined up to 12KHz or so.

 

[rbrucecarter5]

I've actually never heard a SuperRadio 1. (I've owned a couple of SuperRadio IIIs, as well as the Radio Shack clone). Was the SuperRadio 1 REALLY narrow? The SuperRadio III is quite wide (of course, everyone knows that). Now the old Panasonic RF2200, THAT thing was narrow (and unbelievably sensitive!)

Yes - very narrow. The 3 is much wider even in narrow position - leakage through several transistor switches that were added to the design so a wide bandwidth could be selected.

A little thing called the gain / bandwidth product makes for the sensitivity. The 1 is narrow enough it even lessens second adjacent IBOC hash.

 

[kevtronics]

Isn't the upper frequency response on AM-HD "replicated" (IBOC-speak for "faked" or, if you prefer, "electronically reprocessed to simulate actual audio") above 4.5 kHz WITHIN the receiver? This would explain the counterintuitive 4.4 kHz bandpass for the AM section.

This appears to be the source of many listeners' objections to IBOC-AM sound. The codec doesn't do a very good job of simulating the analog waveforms; it can't keep up, hence the "chorusing" or "metallic" effect many listeners find objectionable. Most stations using IBOC-AM that I've heard sound like a bad internet audio stream. Literally the only positive is the lower noise floor.

AM HD's digital audio (at 36 kbps) is entirely synthetic above 5.2 kHz.

For FM HD at 96 kbps, the the faked highs begin at around 9 kHz.

 

[Radioman100]

AM HD's digital audio (at 36 kbps) is entirely synthetic above 5.2 kHz.

For FM HD at 96 kbps, the the faked highs begin at around 9 kHz.

Really? I suppose iBiquity gave you the details on the HDC? Mind sharing them with the rest of the class?

 

[LinoNYC]

AM HD's digital audio (at 36 kbps) is entirely synthetic above 5.2 kHz.

For FM HD at 96 kbps, the the faked highs begin at around 9 kHz.

Really? I suppose iBiquity gave you the details on the HDC? Mind sharing them with the rest of the class?

I've seen (and maybe able to find) a spectral analysis of the AM and although his assesment is correct, I do recall seeing SBR commecing at a slightly lower frequency, perhaps 4.7 khz.

The FM is more problematic, 96kbps requires the use of the full alotted subcarrier, as more channels are added, this gets subdivded so I'd expect the replication to begin at a lower frequency.


Lino

 

[JohnnyElectron]

Is AM HD always at 36KB? XM SatRad does a hell of a lot more at 32KB then HD does at 36K. It also seems like digital would be a whole lot more robust than what it is - I'm surprised it doesn't 'go as far as you would think' - if you have a clean analog, you should get HD, but you don't - at least not on my two radios.

 

[LinoNYC]

Is AM HD always at 36KB? XM SatRad does a hell of a lot more at 32KB then HD does at 36K. It also seems like digital would be a whole lot more robust than what it is - I'm surprised it doesn't 'go as far as you would think' - if you have a clean analog, you should get HD, but you don't - at least not on my two radios.

FRom what I have read the AM bitrate is fixed. We could have had a better codec if the developers had been willing to license one from Real Networks or even used the open source OGG, but this what you get when the Government allows the "free market" to decide a standard. Ibiquity wanted to nail-down all aspects and make them subject to license. If we'd had a better administration in Washington things might have turned-out better. Ironicly, their TX server runs on Linux!

BTW: I've heard sat radio repeatedly in cars and stores, it doesn't sound that great. I guess it's a matter of what flaws you are used to.

Lino

 

[Radioman100]

FRom what I have read the AM bitrate is fixed. We could have had a better codec if the developers had been willing to license one from Real Networks or even used the open source OGG, but this what you get when the Government allows the "free market" to decide a standard. Ibiquity wanted to nail-down all aspects and make them subject to license. If we'd had a better administration in Washington things might have turned-out better.

Do you really think that would have made any difference? After all, Bill Clinton, the Democrat's Democrat signed the telecom bill of '96, not a Republican.

It seems to me like he endorsed the "free market" in a big kind of way, and it has cost thousands of broadcasters their jobs.

If a Clinton had been in the White House, I assure you, things would have turned out exactly the same with iBiquity.

 

[ve3jf]

Is AM HD always at 36KB? XM SatRad does a hell of a lot more at 32KB then HD does at 36K. It also seems like digital would be a whole lot more robust than what it is - I'm surprised it doesn't 'go as far as you would think' - if you have a clean analog, you should get HD, but you don't - at least not on my two radios.

The AM system actually has two streams: a 20 kb/s "core" stream, carrying mono audio, and a 16 kb's "enhanced" stream, which can be combined with the core stream to provide stereo audio. The core stream is carried by the primary digital sidebands (the ones at 10-15 kHz from the carrier, causing all the havoc to adjacent channel stations), while the enhanced stream is carried by the other two sidebands, in the 0-10 kHz region. According to the test results produced by iBiquity, the enhanced stream is less robust than the core stream, so the stereo service area should be smaller than the mono service area. In most published reports that show actually measured coverage, however, they are very cagey about this difference, and never mention whether the decoded audio is stereo or not. Curiously, none of the anecdotal observations I've seen recently mention whether stereo audio is being received. It's not even clear whether all AM HD stations are actually transmitting a stereo signal. Comments?

Barry