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AM HD TURNOFF PACE ACCELERATES
- Thread starter Savage
- Start date
TheBigA said:
Reality is showing you the facts. I'm just fleshing out facts with anecdotal information.
When I further illustrate by explaining the simplest technical fundamentals which fully support assertions others and I have made,
these are not dealt with, but instead you return us to the specific examples of humans which you dismiss as anecdotes.
If you never read the US Digital radio white papers years before this happened, then GET a copy.
It clearly states that the AM version will make wideband noise and outlines in advance the tortured mentality by which such
noise will be ignored. Sometime well before 2000 I was working in Livonia Michigan on RS232/422 interface issue and another field service person from Poughkeepsie NY handed me a copy he had printed out, thinking I might be interested.
When I had lunch that day, I read most of it, and my first thought was the FCC would never approve the AM version,
because it would have to produce exactly as much noise as described. But it did get approved.
Unless a specially dumbed down radio is used, or a commuications receiver, the audio WILL contain hiss.
That would be most radios in existence.
Some listeners may have profound upper end hearing loss, and hiss cannot annoy them as much. Lost sibilants DO, though.
Those without hearing loss are simply being trained to think AM sounds like having -20 db hearing protection earplugs
all the time, except that there's this hissing or mushyness, so let's not listen to THAT station at all. Too weak.
There have been steps made which have mitigated some of the noise, maybe as much as 5 db during the years this experiment
has gone on.
I weary of offering facts to the closed-of-mind.
Here's just one last one to consider: WGN and WLS seem to have decided it's not worth it.
Tom Wells said:
Casting insults isn't a replacement for facts, which once again you've not provided.
I asked for quantitative facts on affects of HD on signal and audience. You refer me to some unlinked white paper. That's not facts. I'm not asking for a lot.
Tom Wells said:
That's nice to know, but irrelevant. Those stations that choose to use it have not experienced any quantitative audience loss as a specific result of it. In fact WBBM-AM, which encodes HD, has more audience than WGN and WLS. I'm not saying that HD is the reason, but it certainly hasn't hurt. And no, Savage, it hasn't helped either. But NOT using it hasn't helped GN or LS either.
TheBigA said:
Then provide some proof it HASN'T helped WGN or WLS to stop using it.
In competetion, dead weight must be trimmed off, and what's not helping will be quickly discarded.
WBBM is short term radio by definition. Their cycle is so short there's no reason to stay tuned, unless you're in a vegetative state.
They cannot be compared in any way to WGN and WLS, and you're welcome to see WBBM as competing with WLS and WGN,
but they are apples and oranges.
Even I can stand a few minutes of hiss listening to WBBM if I'm hoping to check road conditions etc.
I apologize if you take oblique commentary as insult. I suppose I should have just said "Argghh!"
It's nothing specifically YOU, per se. It's a whole world of chosen closed mindedness enforced by media/marketing.
It seems you are speaking from some sort of elevated balcony, and I'd really like to converse at street level.
As a skid mark between electronic behavior and the expectations of users, I daily
deal with with people who simply want things to work, while absolving themsleves of any responsibiliites.
A fixation upon metrics tied to monetization has been so helpful, the entire world is now enjoying the abundance
provided by such smart economics. Daily new stories erupt about how people's investments have gone wildly sucessful, right?
HD AM works as well junk derivatives. Get some money from these suckers, then amscray.
It's almost never about making things work better or learning how to understand things better, take better care of things,
or how to more effectively use anything already exisiting, that's never profitable enough.
Going back to old boring responsible finances and radio modes is just not exploitative enough to satisfy modern greed and gluttony.
Isn't it just about time for the taxpayers to bail out the banks again?
Until you acknowledge facts regarding AM modulation, not much more progress is possible.
Denying such facts makes it much easier to believe that self-interference could be irrelevant.
Tom Wells said:
I did. The ratings. WBBM-AM's cume is about the same as WGN and WLS put together. A few years ago, both of those stations were rated higher.
Tom Wells said:
Which "facts" are you talking about? All I read is a lot of subjective comments that are unworthy of an engineer. As you well know, a scientist deals in quantitative facts, and so far, you've presented none.
Once again:
Fact No 1. AM modulation principle
AM modulation results when two frequencies are combined, one of them being an
audio range frequency, and the other, any useful frequency that can be made to propogate wirelessly.
With no modulation, all power is in the "carrier".
As modulation increases, and/or more complex audio is mixed with the rf, less and less power is in the carrier,
and more power is distributed in the complex sidebands until the carrier disappears at full modulation peaks.
No analog modulation of any kind can be mixed in that does not somehow subtract power from the carrier.
Even if someone has defined 5 khz as no longer audio, if it didn't subtract power from the carrier it would not exist.
Dissent/discussion/contention or agreement?
Fact No 1. AM modulation principle
AM modulation results when two frequencies are combined, one of them being an
audio range frequency, and the other, any useful frequency that can be made to propogate wirelessly.
With no modulation, all power is in the "carrier".
As modulation increases, and/or more complex audio is mixed with the rf, less and less power is in the carrier,
and more power is distributed in the complex sidebands until the carrier disappears at full modulation peaks.
No analog modulation of any kind can be mixed in that does not somehow subtract power from the carrier.
Even if someone has defined 5 khz as no longer audio, if it didn't subtract power from the carrier it would not exist.
Dissent/discussion/contention or agreement?
Of course HD is an "analog" modualation, as it referenced to a continuous function, the carrier.
And, by being part of the wide range of "audio" frequecies not only are there products related to the carrier, there
are hamonics created referenced to all the "audible" frequencies.
None of the audio created by HD is directly useful to humans, and the reduction in modulation and audio bandwidth
necessary are only further detriment to intelligibilty.
The sum of all the products produced subtract from the power remaining in the carrier.
In the case of high level modulation, at 100%, the total instananeous power is the power of the carrier plus another
50%, the additional power comes from the audio amplifier itself.
PWM transmitters simply have real-time addressable power modules to create the same waveform as would be producd by
the more elementary method.
I don't think I suggested the HD sidebands were not still an "analog" modulation.
If it is audible and created by the station itself, then it is analog modulation.
In cases where an amplifier stage develops an rf parasitic oscillation due to failing capacitors, etc,
even though the product may be above the bandwidth of the transmitter/antenna, the reduced power and mushy sound
produced is well known and understood.
Until the "undesired" oscillaltion is cured, the full power that should available to give to the "desired" audio is limited.
And, by being part of the wide range of "audio" frequecies not only are there products related to the carrier, there
are hamonics created referenced to all the "audible" frequencies.
None of the audio created by HD is directly useful to humans, and the reduction in modulation and audio bandwidth
necessary are only further detriment to intelligibilty.
The sum of all the products produced subtract from the power remaining in the carrier.
In the case of high level modulation, at 100%, the total instananeous power is the power of the carrier plus another
50%, the additional power comes from the audio amplifier itself.
PWM transmitters simply have real-time addressable power modules to create the same waveform as would be producd by
the more elementary method.
I don't think I suggested the HD sidebands were not still an "analog" modulation.
If it is audible and created by the station itself, then it is analog modulation.
In cases where an amplifier stage develops an rf parasitic oscillation due to failing capacitors, etc,
even though the product may be above the bandwidth of the transmitter/antenna, the reduced power and mushy sound
produced is well known and understood.
Until the "undesired" oscillaltion is cured, the full power that should available to give to the "desired" audio is limited.
Tom Wells said:
Wrong. All radio averages about 11 or 12 minutes average listening spans. The PPM has shown us that listening for hours on end is not a reality.
People are interrupted by things at work, in the car and at home (the three locations where, in each, about a third of radio listening take place). It does not matter whether it's a music FM or a talk AM or an news AM, the average listening times are just about the same.
The difference is that listeners return to stations that please them many times... after a lunch break, after a phone call, after taking the trash out.
The average listening "time per incident" to WGN, WLS and WBBM is about the same.
Tom Wells said:
Ratings or "metrics" have been used to evaluate radio since the early 30's. This was also the time when marketing companies like Proctor & Gamble determined that they could develop new products with the help of research and consumer feedback.
"Metrics" or ratings are just a way for stations to get feedback from listeners about what they like. For advertisers, it is a way to determine which stations can justify higher prices and which can not.
Ratings have nothing to do with the crises of the recession, new media and whatever else has happened to radio.
richllewis said:
Clear Channel skipped over Jackson entirely with HD, or at least that was the case when I lived in the state a few years ago. The only HD in Jackson is MPB and Jackson State's jazz and news public radio station. MPB's statewide HD network is really, really good and has some strong HD coverage.
As for Memphis, my understanding is WDIA has gone through some issues at their transmitter site. Either tower trouble or flooding trouble or both, I forget exactly what, so they have been running lower power on an STA for a long time.
But my guess would be that WDIA, being an actual icon of broadcast radio in Memphis and still very heavily listened to by a VERY loyal core audience, got complaints about the sound quality so they turned it off. Or maybe it just broke.
The WREC site never flooded during the recent incidents and never went off the air during the worst of it. In fact I think one of the other Memphis stations, maybe WDIA, was using WREC's site for a while as emergency facilities.One more time... WGN radiates a 50,000 watt carrier at all times. If WGN 100% modulates, 720 will radiate 75,000 watt signal. 50kw for the carrier plus 25kw in sidebands. In an analog AM signal at 100% modulation, 1/3 of the power is in the sidebands.
Should WGN decide to add IBOC, at 100% modulation the analog carrier will be 50,000 watts. The analog sidebands will add 25,000 watts to the signal -- exactly the same as if they didn't run IBOC. The IBOC signal is a completely different animal. It currently runs at -20dBc. This means the IBOC would radiate a 500watt QAM signal using OFDM. This OFDM basically provides a "constellation" of data. The orthogonal carriers provide a Y axis component to produce a lattice that maintains a means of coordinating this data constellation into a useable QAM output. Unlike analog, which produces a constant carrier output augmented by modulation percentage, the QAM signal produces a steady RF output regardless of modulation. IBOC has no effect on the analog carrier or it's modulation levels. Analog has no effect on IBOC's signal. When an analog signal is unmodulated, only the carrier is emitted. IBOC emits a constellation of data regardless of modulation percentage.
One more thing: Take a sweep generator and check the IF response of as many different AM receivers as you wish. Get back to me with how many of them have -3dB down points much above 3,500Hz.
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Should WGN decide to add IBOC, at 100% modulation the analog carrier will be 50,000 watts. The analog sidebands will add 25,000 watts to the signal -- exactly the same as if they didn't run IBOC. The IBOC signal is a completely different animal. It currently runs at -20dBc. This means the IBOC would radiate a 500watt QAM signal using OFDM. This OFDM basically provides a "constellation" of data. The orthogonal carriers provide a Y axis component to produce a lattice that maintains a means of coordinating this data constellation into a useable QAM output. Unlike analog, which produces a constant carrier output augmented by modulation percentage, the QAM signal produces a steady RF output regardless of modulation. IBOC has no effect on the analog carrier or it's modulation levels. Analog has no effect on IBOC's signal. When an analog signal is unmodulated, only the carrier is emitted. IBOC emits a constellation of data regardless of modulation percentage.
One more thing: Take a sweep generator and check the IF response of as many different AM receivers as you wish. Get back to me with how many of them have -3dB down points much above 3,500Hz.
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Perhaps I am misleading by not specifying "Instantaneous power output."
Agreed that full modulation of a 50kw is 75kw, the carrier plus the audio, but that's the positive side of the modulation.
At the instaneous opposite half of the sine wave, the audio is not adding the amplitude, it's subtracting.
If the audio modulation becomes too high, the waveform becomes discontinuous, and we hear splatter across a MUCH
wider bandwidth. The RF envelope is then "pinched off" and the square cornered waveform produces many products
that only sound bad. Either on that frequency, or adjacents.
I agree that the iboc "constellation" is, unchanging, 500 watts on a 50 kw.
The terminolgy is much like calling a migrane headache a "halo".
Five hundred watts of screeching interference which would have been available for the "human-intended" modulation.
Analog modulation certainly has an effect on a iboc signal. If it's too high, and the carrier pinches off, there's no carrier left
for the constelaltion to be relative TO, and then decode drops.
Which is why ibiquity states that neagtive modualtion peaks MUST be limited at -94% in order to insure
the carrier is always still somewhat there.
IF response, width and skirt shape vary all over the place.
IF response also varies by what frequency is chosen.
I have a high preference for AM using 262.5 khz.
Then, too there "hi-fidelity" flat-top IF "stagger tuning" that permits center tuning while still keeping high frequencies
in balance.
There's coils with overcoupling, unity coupling and undercoupling.
These all "behave" differently.
The whole point of "tuning" is to select the user's desired sound.
The "average" radio, up until the point at which fixed tuning steps were introduced, was about 6 db down at 10 khz.
This would permit side tuning of local stations to achieve a balance between low and high frequencies
that was as crisp or dull as desired.
In cases of listening to strong distants, the frequency balance was usually pretty good center tuned,
and the 10 khz whistle was still audible, but center tuning allowed the user find a minimum point.
I might have a few radios areound here as dull as 3 db down at 3500.
Any of the radios with magnetic "can" headphones, for sure.
1927 Atwater Kent model 35
1934 Philco cheapie cathedral
1930 Majestic Super screen grid
A few really cheap 5 tube AMs
Last would be my wife's Kenwood HD car radio.
I really must make an aircheck of how weird it sounds on AM.
The sensitivity is fine now that it has a real whip antenna, but even a telephone landline never sounded so bad.
It can't be tuned at all, it only has fixed preset "steps".
Maybe the IF reponse is wide enough to sound OK, but we'll never know because there's no way to tune it.
Even the Collins R390 A in the 4khz filter mode has enough crispness to enjoy most signals, if not center tuned.
Once the IF bandwidth gets that narrow, the ability to tune continuously becomes more important.
Agreed that full modulation of a 50kw is 75kw, the carrier plus the audio, but that's the positive side of the modulation.
At the instaneous opposite half of the sine wave, the audio is not adding the amplitude, it's subtracting.
If the audio modulation becomes too high, the waveform becomes discontinuous, and we hear splatter across a MUCH
wider bandwidth. The RF envelope is then "pinched off" and the square cornered waveform produces many products
that only sound bad. Either on that frequency, or adjacents.
I agree that the iboc "constellation" is, unchanging, 500 watts on a 50 kw.
The terminolgy is much like calling a migrane headache a "halo".
Five hundred watts of screeching interference which would have been available for the "human-intended" modulation.
Analog modulation certainly has an effect on a iboc signal. If it's too high, and the carrier pinches off, there's no carrier left
for the constelaltion to be relative TO, and then decode drops.
Which is why ibiquity states that neagtive modualtion peaks MUST be limited at -94% in order to insure
the carrier is always still somewhat there.
IF response, width and skirt shape vary all over the place.
IF response also varies by what frequency is chosen.
I have a high preference for AM using 262.5 khz.
Then, too there "hi-fidelity" flat-top IF "stagger tuning" that permits center tuning while still keeping high frequencies
in balance.
There's coils with overcoupling, unity coupling and undercoupling.
These all "behave" differently.
The whole point of "tuning" is to select the user's desired sound.
The "average" radio, up until the point at which fixed tuning steps were introduced, was about 6 db down at 10 khz.
This would permit side tuning of local stations to achieve a balance between low and high frequencies
that was as crisp or dull as desired.
In cases of listening to strong distants, the frequency balance was usually pretty good center tuned,
and the 10 khz whistle was still audible, but center tuning allowed the user find a minimum point.
I might have a few radios areound here as dull as 3 db down at 3500.
Any of the radios with magnetic "can" headphones, for sure.
1927 Atwater Kent model 35
1934 Philco cheapie cathedral
1930 Majestic Super screen grid
A few really cheap 5 tube AMs
Last would be my wife's Kenwood HD car radio.
I really must make an aircheck of how weird it sounds on AM.
The sensitivity is fine now that it has a real whip antenna, but even a telephone landline never sounded so bad.
It can't be tuned at all, it only has fixed preset "steps".
Maybe the IF reponse is wide enough to sound OK, but we'll never know because there's no way to tune it.
Even the Collins R390 A in the 4khz filter mode has enough crispness to enjoy most signals, if not center tuned.
Once the IF bandwidth gets that narrow, the ability to tune continuously becomes more important.
You have analog QAM and digital QAM confused. CQUAM limited negative peaks at 96% modulation because at maximum modulation, the carrier is phase shifted relative to the linear sidebands. This difference results in an effective carrier that instantaneously appears to be 96% of what it should be to the sidebands. Negative modulation peaks are limited to 96% for THAT reason. There are no such constraints with an IBOC analog OR digital signal.
iyiyi said:
No, there are no such constraints, but running the modulation past the point where the carrier is so weak or neutralized that there is
no reference for the constellation, the "bits" in the constellation do not "exist".
Sufficent data redundancy, buffering, and high/low data modes permit some loss of data.
If you have a suggestion for how the constellation can exist without reference to a "somewhat" continuous rate function such as a sine wave or even a square wave, please elaborate.
Even though the power available in the "carrier" varies as modulation subdivides the power into sdiebands, enough remains
(if not cut off completely) to provide reference for the 500 watts of data modulation at the frequencies above 5 khz.
I've never had occasion to find that my mind has generated "false facts", so I can generally consider that when my mind tells
me I've read something factworthy AND it fits in with reality as I have experienced and been taught in radio engineering school,
then it's a fact, amd I retain it for reference at times such as this.
Please cite ibiquity documentation that would suggest uncontrolled, over 100% negative modualtion peaks are "just fine".
Even the digital-only ibiquity AM method REQUIRES a small "vestigal" carrier for the bits to be referenced to.
richllewis said:
I was in Mississippi and Alabama a few weeks ago. The MPB station in Meridian, MS had consistent signal in HD in Union, Mississippi and Silas, Alabama. I also heard some HD stations in Mobile, Alabama. I was listening to gospel quartet music on WKSJ 94.9 and the HD was a few seconds behind the analog.
muiscmike said:
Yeah there's been a mismatch for a month or two now. The HD went off a while back, and when it came back on, the audio was all screwed up, sounding really warbly and tinny in HD on the main channel but basically OK on the HD-2. Been like that, with the bad delay, ever since.
You're thinking of the defunt Magnavox PMX AM Stereo system, which required negative modulation to be limited to -95% to prevent the receiver from "popping". C-Quam does not have this problem, and can be fully modulated to -100%.iyiyi said:
The cosine correction in the receiver's C-QUAM decoder chip does reach its maximum level at this point, so you may hear some distortion in a stereo receiver as the carrier approaches pinchoff, but there is no objectionable popping noise, and no technical requirement -- either by Motorola or by the FCC -- that the negative modulation must be limited below -100%.
WLW has had their IBOC off for a few days. I hope it stays off and they return to their 10-15 khz bandwidth. Their audio used to sound delightful on a wide band radio. If fact, most cheap radios have a wide bandwidth and AM can sound fairly good on them. I'll gladly give up receiving WOR at night in return for a better sounding WLW. I hope their engineers read these posts. Leave IBOC on the FM band where it works better.
Just turn it off and go back to stereo
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