Please Explain to me...

[HHalland]

How AM HD is supposed to work? Is there a second channel of stuff or is it just the same crummy program? The HD radio I bought makes everything sound the same, boomy and flat. Analog and HD both sound crappy. Although s guy I was talking to at the store told me after I bought this radio that there are no HD stations that come in here way Northeast of San Fransisco. So am I hearing HD or am I hearing regular? AM radio sounds the same, and the FM is boring and sounds like a cassette tape that I left on my dashboard. Overall there is no WOW fraction for all of the money I spent. I can not even hear DX ANYMORE as the radio is not sensitive at all, and I don;t like it, but I can't send it back becasue it was a B-Stock radio and it sounds like crap. I liked my Sony AM Stereo radio for DXing and it still sounds better. This is a sham. It's like everyone telling me that Starbuck makes good coffee. It's not good. I like Denny's

 

[Tom Wells]

Same program on AM HD. You probably are not receiving in HD, because the audio is "quite different" by intent.

The analog reception is high-frequency limited by design, so that when HD pops in, you go "WOW!"
Of course, it sounds clippy and sparkly, but contains high frequencies now (necessarily) removed from the analog output.
If this were not done, the high-frequency "events" would confuse decoding of the HD sidebands, now occupying space that would have been used to transmit such information in analog.
This trick fools those not wise to the game.

The sensitivity is low enough that the digital display clock frequency noise does not intrude into the analog performance.

You are right about the coffee analogy. Starbucks is "well marketed". Not necessarily good coffee, but it is sold as such.
I like a good dark roast coffee, and S-bucks just doesn't cut it.

No FM HD? At least on FM, the IBOC detriment to the analog is arguably minimal, whereas in AM, there is no benefit and great harm caused.

 

[Mike Walker]

Come on Tom...measurements of the ANALOG SECTION of the Sangean tuner show flat response to 15khz under strong signal conditions.

Like many (most car units) tuners and receivers, most HD radios blend and gradually suppress high frequencies as signal level drops...so that the listener WILL NEVER HEAR NOISE, whether listening to analog or digital signals.

Given a strong signal (WKBC-FM here in Wilkes County, or WFDD in Winston Salem), analog FM sounds fantastic on the Accurian. Except for a narrower stereo image, and loss of highs FROM THE 75us PRE-EMPHASE REQUIRED FOR ANALOG FM, it's fairly close to "HD".

HD sounds brighter than FM because, as anyone who's an engineer at an FM station will tell you, an FM station can be bright, or it can be loud. It can't be both, because with the treble boost from the 75us pre-emphasis, 100 percent modulation is reached MUCH SOONER at high frequencies. In order to be able to modulate fully in the midband, where the ear perceives loudness, highs MUST be rolled off. Pre-emphasis (boosting highs during transmission) and de-emphasis (cutting them on playback) is done on FM for the same reason that dolby does it on tape...to reduce hiss (and yes I'm aware that while dolby is "dynamic"...varying in response to the recorded audio, FM's pre-emphasis/de-emphasis is constant regardless of audio content).

HD has no such limitations...no pre-emphasis...so a station can use lots of loudness processing (compression/limiting), and still be BRIGHT. So EVERY HD signal has more high frequency content than it's analog counterpart. FULLY EXTENDED, full modulation highs with negligible distortion...in other words IMPROVED CLARITY is one of the greatest advantages of HD.

If Tom is correct, then when you compare HD on one radio, with analog on another, the analog should sound as good...and spectral balance (bass/midrange/terble) should be about the same. I ENCOURAGE YOU TO TRY IT! The results will be the same as with the HD radio when it switches to digital...HD will be FAR brighter and clearer. And it's not an "artifact"...in the studio, the HD sounds much closer to the original (cd or mic input) than does the analog signal. It measures that way, too!

I'm guessing that maybe you bought the Polk or Boston Acoustics HD radio. Both have that "warm/fuzzy sound" that many enjoy. It's a characteristic of the radio, NOT HD (you can tell because, as you pointed out, ALL sources sound that way...not just HD.)

 

[amfmsw]

Close. Dolby B is constant pre/de-emphasis.

Dolby C is dynamic, and unless the operator really knows what they're doing, turns everything to mud if the levels aren't loud enough. Or just as bad, choppy sounding, like bad recording tape with drop-outs,

 

[700WLW]

HD sounds brighter than FM because, as anyone who's an engineer at an FM station will tell you, an FM station can be bright, or it can be loud.

There is no difference, between analog FM and the supposed CD-like quality of FM HD - FM HD actually sounds worse, because the the digital artifacts. And yes HHalland, you are correct, in assuming that HD Radio is a farce (in so many words) - programming the HD channels is not a priority, with job cut-backs/consolidation. The HD channels are just more of the same repetitive terrestrial radio, and will eventually contain commercials (there are only a few tens-of-thousands listeners), if there are ever enough listeners, which will never happen. Reception of the HD channels is problematic, even with, externally-mounted FM dipole and AM-loop antennas.

 

[Tom Wells]

Come on Tom...measurements of the ANALOG SECTION of the Sangean tuner show flat response to 15khz under strong signal conditions.

Like many (most car units) tuners and receivers, most HD radios blend and gradually suppress high frequencies as signal level drops...so that the listener WILL NEVER HEAR NOISE, whether listening to analog or digital signals.

Given a strong signal (WKBC-FM here in Wilkes County, or WFDD in Winston Salem), analog FM sounds fantastic on the Accurian. Except for a narrower stereo image, and loss of highs FROM THE 75us PRE-EMPHASE REQUIRED FOR ANALOG FM, it's fairly close to "HD".

HD sounds brighter than FM because, as anyone who's an engineer at an FM station will tell you, an FM station can be bright, or it can be loud. It can't be both, because with the treble boost from the 75us pre-emphasis, 100 percent modulation is reached MUCH SOONER at high frequencies. In order to be able to modulate fully in the midband, where the ear perceives loudness, highs MUST be rolled off. Pre-emphasis (boosting highs during transmission) and de-emphasis (cutting them on playback) is done on FM for the same reason that dolby does it on tape...to reduce hiss (and yes I'm aware that while dolby is "dynamic"...varying in response to the recorded audio, FM's pre-emphasis/de-emphasis is constant regardless of audio content).

HD has no such limitations...no pre-emphasis...so a station can use lots of loudness processing (compression/limiting), and still be BRIGHT. So EVERY HD signal has more high frequency content than it's analog counterpart. FULLY EXTENDED, full modulation highs with negligible distortion...in other words IMPROVED CLARITY is one of the greatest advantages of HD.

If Tom is correct, then when you compare HD on one radio, with analog on another, the analog should sound as good...and spectral balance (bass/midrange/terble) should be about the same. I ENCOURAGE YOU TO TRY IT! The results will be the same as with the HD radio when it switches to digital...HD will be FAR brighter and clearer. And it's not an "artifact"...in the studio, the HD sounds much closer to the original (cd or mic input) than does the analog signal. It measures that way, too!

I'm guessing that maybe you bought the Polk or Boston Acoustics HD radio. Both have that "warm/fuzzy sound" that many enjoy. It's a characteristic of the radio, NOT HD (you can tell because, as you pointed out, ALL sources sound that way...not just HD.)

My comments about audio with limited upper-end only refer to the AM signal transmitted when AM HD is in use.
The tuner and amp are likely flat to 20khz, but the audio at the station MUST be limited to avoid interfering with the HD sidebands.
I wonder what the "effective IF bandwidth" is of the AM RF/IF/detector with analog AM service?

 

[Mike Walker]

am/fm/sw you are absolutely wrong. ALL flavors of dolby are dynamic (including the original dolby a, which was a professional format). That's why 3 head dolby cassette decks (and fm tuners with dolby back in the 70s) use(d) a reference tone to set the "dolby level". Tracking of the dolby circuit requires that the input and output level be brought to standard level, and bias and equalization properly adjusted for EACH TAPE USED. Dolby FM stations used to broadcast the reference tone once or twice a week so people with dolby FM could adjust the reference level. "95 Q" (WROQ) in Charlotte used to do it at midnight a couple of times a week...I think Sunday and Wednesday night...so audio nerds could set up their dolby decoders for proper decoding.

This page gives a pretty good description of how various noise-reduction techniques work. Note: dolby b is a simplified version of dolby a, and as such it compresses/expands only low level signals which would otherwise be swamped by noise. Dolby a splits the audio spectrum into three bands, dolby b only one. That's the only difference. Since there is only one band, dolby b is less succeptible to mistracking artifacts than, say, dolby c...but they can still be quite audible.

 

[Mike Walker]

Tom...I thought you were talking about FM HD (vs analog) in your comparison. I was obviously wrong, and apologize. I get a little on-edge here having do defend EVERY idea. Geez! I'm sure you can understand.

As for AM, I think you'll agree with me that ANY reduction in audio bandwidth on analog AM to "make room for HD" is clearly the work of Satan!

 

[1q2w3e]

Tom...I thought you were talking about FM HD (vs analog) in your comparison. I was obviously wrong, and apologize. I get a little on-edge here having do defend EVERY idea. Geez! I'm sure you can understand.

As for AM, I think you'll agree with me that ANY reduction in audio bandwidth on analog AM to "make room for HD" is clearly the work of Satan!

Having set up an AM HD staiton myself...

there is no need to limit the bandwidth of the AM analog signal to 5kHz. As a matter of fact, on the iBiquity software (on the exciter) you can set the analog for 8kHz or 5kHz bandwidth. Knowing that many AM stations have limited the bandwidth to around 5 Khz already (even before Clear Channel made it their mandate), you will basically have no change in audio before or after an HD implementation.

Any noise on the analog signal is due to non-linearities of either the antenna system (more than likely) or the tranmsitter (less likely). And yes I have heard a number of AM stations have some noise on their analog signal. In ALL instances, the engineer was working very hard to get the linearity corrected.

Some stations have tried to implement HD without scanning and sweeping their antenna system. If they did, they would find that they have have some phasing issues that only appears at the extreme ends of their channel. Hense the non-linearities.

In one of my instances... I needed to shift the phase to the input of the phasor by adding some feedline. This rotated the Smith chart to a more linear plot, giving a more linear output and no noise on the analog signal.

 

[EasyPeazy]

Tom...I thought you were talking about FM HD (vs analog) in your comparison. I was obviously wrong, and apologize. I get a little on-edge here having do defend EVERY idea. Geez! I'm sure you can understand.

As for AM, I think you'll agree with me that ANY reduction in audio bandwidth on analog AM to "make room for HD" is clearly the work of Satan!

Having set up an AM HD staiton myself...

there is no need to limit the bandwidth of the AM analog signal to 5kHz. As a matter of fact, on the iBiquity software (on the exciter) you can set the analog for 8kHz or 5kHz bandwidth. Knowing that many AM stations have limited the bandwidth to around 5 Khz already (even before Clear Channel made it their mandate), you will basically have no change in audio before or after an HD implementation.

Any noise on the analog signal is due to non-linearities of either the antenna system (more than likely) or the tranmsitter (less likely). And yes I have heard a number of AM stations have some noise on their analog signal. In ALL instances, the engineer was working very hard to get the linearity corrected.

Some stations have tried to implement HD without scanning and sweeping their antenna system. If they did, they would find that they have have some phasing issues that only appears at the extreme ends of their channel. Hense the non-linearities.

In one of my instances... I needed to shift the phase to the input of the phasor by adding some feedline. This rotated the Smith chart to a more linear plot, giving a more linear output and no noise on the analog signal.

Moreover, how many receivers manufactured in the last 15 years even approach 5 kHz?

I'd be surprised if most of the non-HD car radios manufactured today crack 4 kHz.

 

[1q2w3e]

Tom...I thought you were talking about FM HD (vs analog) in your comparison. I was obviously wrong, and apologize. I get a little on-edge here having do defend EVERY idea. Geez! I'm sure you can understand.

As for AM, I think you'll agree with me that ANY reduction in audio bandwidth on analog AM to "make room for HD" is clearly the work of Satan!

Having set up an AM HD staiton myself...

there is no need to limit the bandwidth of the AM analog signal to 5kHz. As a matter of fact, on the iBiquity software (on the exciter) you can set the analog for 8kHz or 5kHz bandwidth. Knowing that many AM stations have limited the bandwidth to around 5 Khz already (even before Clear Channel made it their mandate), you will basically have no change in audio before or after an HD implementation.

Any noise on the analog signal is due to non-linearities of either the antenna system (more than likely) or the tranmsitter (less likely). And yes I have heard a number of AM stations have some noise on their analog signal. In ALL instances, the engineer was working very hard to get the linearity corrected.

Some stations have tried to implement HD without scanning and sweeping their antenna system. If they did, they would find that they have have some phasing issues that only appears at the extreme ends of their channel. Hense the non-linearities.

In one of my instances... I needed to shift the phase to the input of the phasor by adding some feedline. This rotated the Smith chart to a more linear plot, giving a more linear output and no noise on the analog signal.

Moreover, how many receivers manufactured in the last 15 years even approach 5 kHz?

I'd be surprised if most of the non-HD car radios manufactured today crack 4 kHz.

Excellent point....

If you look on www.nrscstandard.com you will find a whole report on what typical AM radios do with their audio response. They also found out that more people like the 5 - 6kHz range when listening to AM radio. Now that will depend on the program material and all, but to me as an engineer that came as a surprise.

It is a very eye opening report!

 

[SUPERCASTER]

I clicked on your link (above) and was totally amazed and surprised by the

very eye opening report!

Like most HD supporters false claims, just more and more empty promises.
The latest, false, HD Radio sales pitch is that HD radios decode Motorola C-Quam stereo.
Some people will do or say anything to profit from, and promote, their defective products, and false agenda.

 

[EasyPeazy]

I clicked on your link (above) and was totally amazed and surprised by the

very eye opening report!

Like most HD supporters false claims, just more and more empty promises.
The latest, false, HD Radio sales pitch is that HD radios decode Motorola C-Quam stereo.
Some people will do or say anything to profit from, and promote, their defective products, and false agenda.

I don't think anyone is marketing HD Radios for reception of AM Stereo. A few users have stumbled onto that undocumented feature and have shared it on message boards like this one.

 

[SUPERCASTER]

I clicked on your link (above) and was totally amazed and surprised by the

very eye opening report!

Like most HD supporters false claims, just more and more empty promises.
The latest, false, HD Radio sales pitch is that HD radios decode Motorola C-Quam stereo.
Some people will do or say anything to profit from, and promote, their defective products, and false agenda.

I don't think anyone is marketing HD Radios for reception of AM Stereo. A few users have stumbled onto that undocumented feature and have shared it on message boards like this one.

No C-QUAM decoding on HD radios. That would violate Motorola's patents, and is denied by reps from Sangean.
http://www.radio-info.com/smf/index.php/topic,63680.msg451170.html#msg451170

 

[vsa]

1q2w3e wrote: "...If you look on www.nrscstandard.com you will find a whole report on what typical AM radios do with their audio response. They also found out that more people like the 5 - 6kHz range when listening to AM radio. Now that will depend on the program material and all, but to me as an engineer that came as a surprise..."

More people LIKE the 5 - 6 kHz range??? What an extremely convenient discovery that coincidentally matches iBiquity's needs to a tee!!! By the way, I'll buy TWO of those bridges that you're selling. ;D

 

[EasyPeazy]

No C-QUAM decoding on HD radios. That would violate Motorola's patents, and is denied by reps from Sangean.
http://www.radio-info.com/smf/index.php/topic,63680.msg451170.html#msg451170

Personally I don't care if they decode C-QUAM or not. I'm simply refuting your claim that this is "the latest, false, HD Radio sales pitch."

Your own assertion is that Sangean has said publicly that their radio DOESN'T do this.

If that's the case, how could this possibly be a "false, HD Radio sales pitch?" The people manufacturing the radios are the people trying to sell them.

It doesn't seem to me that they're trying to sell them on this supposed feature.

 

[MotoMuzak]

Hi all, I am back after my general non-existance for a couple months (I had to temporarily suspend my file on here because I was having trouble with my previous E Mail system. Now that I am on Google Mail, this hopefully won't have to happen again. And NO, Radio-Info didn't ban me! I more or less banned myself, so to speak.......)

Actually, a couple (?) very early model/s of Accurian IBAC rigs did support CQuam on AM. Several months ago, whilst at a Portland Radio Shack, I tested one of these radios, tuned to the local Radio Disney station, KDZR 1640. 1640 falls right in the middle of the AM Expanded bandplan, in which all stations in the spectrum 1620-1700 have to be stereo by FCC mandate, reportedly.

Tuned it in and sure enough, there it was in stereo. This was in a store-front (one-story mini mall) Radio Shack listening through headphones. The quality really wasn't that great, supposedly the bandwidth of the AM tuners on those rigs is around 4 KHz or so. But at least it was there.

Apparently CQuam was withdrawn from all the newer (I believe, winter 2006 onward) Accurian IBACs because of licensing problems like Supercaster mentioned above. So far as I can tell there probably won't be any more produced that have CQUAM, at least not that I can see..............

 

[FreddyE1977]

Perhaps someone on this board will be able to answer this question for me.

I don't yet have an HD radio. A few weeks ago I noticed that whenever my local AM
station which carries ESPN switches into day pattern, their audio quality falls off significantly. (It almost sounds as if you are listening over an old-style analog phone line.) The audio goes back to full-quality when they shift back to night pattern. During the day I notice that if I off-tune slightly from their frequency in either direction, I get a strange whirring sound that resembles a dial-up PC modem. Is this station testing in HD, and is that why their analog audio is so lousy during the day? I have emailed their engineering dept. but no one will answer the question.

 

[MotoMuzak]

If you are hearing an AM IBAC (or perjoratively, "H.D. Radio") track, it'll sound like scratchy static, or like a wideband dial-up computer modem (and aside from ISDN, is there such a thing? ;o) Chances are that's what you are hearing.

Try to get a digital-tuned analogue radio (not an IBAC, a regular radio that uses an LCD display and buttons instead of a traditional dial and tuning knob) and tune 10kHz up or down. So if you are listening to a radio station on 800, for example, and it's running IBAC, you'll hear noise on 790 or 810. Depending on your radio's bandwidth you'll likely hear splattering on the regular AM as well. (Sounds like loud static in the background.)

That's why IBAC on AM will never work, no matter what the Iniquity execs and/or engineers seem to think!!!

 

[SUPERCASTER]

Perhaps someone on this board will be able to answer this question for me.

I don't yet have an HD radio. A few weeks ago I noticed that whenever my local AM
station which carries ESPN switches into day pattern, their audio quality falls off significantly. (It almost sounds as if you are listening over an old-style analog phone line.) The audio goes back to full-quality when they shift back to night pattern. During the day I notice that if I off-tune slightly from their frequency in either direction, I get a strange whirring sound that resembles a dial-up PC modem. Is this station testing in HD, and is that why their analog audio is so lousy during the day? I have emailed their engineering dept. but no one will answer the question.