"I-Buzz"

[Mike Walker]

I was in Hickory today, well within earshot of all the stations in the Charlotte, Gastonia, Concord, Belmont area. With the latest issue of Popular Communications in hand, which lists all the AM HD stations in the US, I tried hard to hear any "I-buzz" on the Charlotte area stations I knew to be in HD. I heard none, though admittedly the AM band is pretty damn full in this are. From my car, parked in the lot at Valley Hills Mall, there was something audible at nearly every spot on the dial betwen 550 and 1600...so perhaps the stations booming in were killing any "I-Buzz" on the sidebenad of HD stations. But wait...if the presence of even a very weak signal completely covers "I-Buzz", well...

 

[PocketRadio]

I was in Hickory today, well within earshot of all the stations in the Charlotte, Gastonia, Concord, Belmont area. With the latest issue of Popular Communications in hand, which lists all the AM HD stations in the US, I tried hard to hear any "I-buzz" on the Charlotte area stations I knew to be in HD. I heard none, though admittedly the AM band is pretty damn full in this are. From my car, parked in the lot at Valley Hills Mall, there was something audible at nearly every spot on the dial betwen 550 and 1600...so perhaps the stations booming in were killing any "I-Buzz" on the sidebenad of HD stations. But wait...if the presence of even a very weak signal completely covers "I-Buzz", well...

I've heard WTWP 1500 AM-HD IBUZZ all over WTRI 1520 AM in Maryland, within its protected contour. I talked with WTRI's station owner, and he stated that his lawyers advised that it wasn't worth taking legal action. WTWP's IBUZZ was written up in the WSJ:

"Digital Signals Spark Static From AM Radio "

http://online.wsj.com/public/article/SB114125971438087021.html?mod=todays_free_feature

"WSJ Reports on AM IBOC Interference"

"The WSJ article cites a listener in Elkridge, Md., who has had trouble tuning into WTRI(AM), 1520 kHz, since WTOP, at 1500 kHz in Washington, went HD Radio about a year ago."

http://www.rwonline.com/dailynews/show_issue.cgi?year=2006&month=3&week=9

Protected contour, or not, many AM listeners will be lost and the AM band will self-destruct.

 

[clouseau]

I was in Hickory today, well within earshot of all the stations in the Charlotte, Gastonia, Concord, Belmont area. With the latest issue of Popular Communications in hand, which lists all the AM HD stations in the US, I tried hard to hear any "I-buzz" on the Charlotte area stations I knew to be in HD. I heard none, though admittedly the AM band is pretty damn full in this are. From my car, parked in the lot at Valley Hills Mall, there was something audible at nearly every spot on the dial betwen 550 and 1600...so perhaps the stations booming in were killing any "I-Buzz" on the sidebenad of HD stations. But wait...if the presence of even a very weak signal completely covers "I-Buzz", well...

I've heard WTWP 1500 AM-HD IBUZZ all over WTRI 1520 AM in Maryland, within its protected contour. I talked with WTRI's station owner, and he stated that his lawyers advised that it wasn't worth taking legal action. WTWP's IBUZZ was written up in the WSJ:

"Digital Signals Spark Static From AM Radio "

http://online.wsj.com/public/article/SB114125971438087021.html?mod=todays_free_feature

"WSJ Reports on AM IBOC Interference"

"The WSJ article cites a listener in Elkridge, Md., who has had trouble tuning into WTRI(AM), 1520 kHz, since WTOP, at 1500 kHz in Washington, went HD Radio about a year ago."

http://www.rwonline.com/dailynews/show_issue.cgi?year=2006&month=3&week=9

Protected contour, or not, many AM listeners will be lost and the AM band will self-destruct.

You don't suppose this has anything to do with your consitant recommendations of $9.99 Pocket Radios do you. Mix in a little selectivity. Mike is either lying, or maybe there's an equipment issue. Whadda YOU think??

Or the fact that "THE LAST TIME" you posted this article, Elkridge has not moved any closer to WRTI than before. Radio Locator still calls it "Barely Perceptible" and in the "Fringe" category.

Good call on the no legal action. It's a "Barely perceptible" station at that location. You know that's a step beyond DX or "Distant" right?

Your year old article REPOSTED is just more of the same old "Grand Piano falling down the staircase". Please stop reposting links form a year ago! It makes the board unreadable.

Clouseau

 

[Tom Wells]

I am working in Stevens Point Wisconsin this week, and have been checking the Chicago iBOC AMs.
I am 250 miles out. The sidebands are still evident on all the 50kw AMs in daytime.
This is with the 1972 Motorola AM/FM car radio.
Tuesday night, WSCR 670 left the IBOC on, and WSM 650, which was "clear", had its upper sideband well-hissed.
Center tuned, it hissed. Lower sideband was clear and listenable.
WSM would be 750 miles.

More locally, WJMT AM 730 in Merrill Wisconsin, about 40 miles away is strong here, but has an odd, low mush
in the noise floor regardless of how I tune it. WGN 720 throws a very clear iboc on 710, so 730 is intermod with it also.
There is a weak something on 710, not copyable now, but without the hiss, maybe.
Well, I CAN copy it. It's signing off with the Star Spangled Banner. But I couldn't really "copy".
According to Radio-Locator I am mid-strength signal here for WJMT.
Other AMs not adjacent to IBOCs do not have this low-to medium frequency hiss, only the "normal" noise floor.
This is has been constant during daytime.

On the other hand, I find the sound of the AM IBOCs themselves in Chicago sound much better at this distance,
perhaps because AVC action always seems to result in narrower bandwidth of audio, something I've noticed in all
radios with AVC. Well, communications receivers excepted. The balance of audio seems better, with less
mid-range bass "thickness" in the voices. This makes it easier to hear the sibilant info.

Maybe I need to add a manual RF gain control for use in local reception.
If someone has a radio with wideband IF and manual gain control, try this for us, and see if low sensitivity can
decrease the self-jamming effect, or if the tonal balance seems improved.

 

[Tom Wells]

I was in Hickory today, well within earshot of all the stations in the Charlotte, Gastonia, Concord, Belmont area. With the latest issue of Popular Communications in hand, which lists all the AM HD stations in the US, I tried hard to hear any "I-buzz" on the Charlotte area stations I knew to be in HD. I heard none, though admittedly the AM band is pretty damn full in this are. From my car, parked in the lot at Valley Hills Mall, there was something audible at nearly every spot on the dial betwen 550 and 1600...so perhaps the stations booming in were killing any "I-Buzz" on the sidebenad of HD stations. But wait...if the presence of even a very weak signal completely covers "I-Buzz", well...

Please tell us again what kind of car and radio this was.
Modern car radio design may be so narrowband as to hide any hiss, and you may only hear a "mush" in the noise floor as I describe in the first-adjacent
situation in the previous post. If so, you must compare to other signals of same strength with/without iBOC adjacents before you decide you can't hear the
intermod of iBOC and analog signals.

In the example I note with WJMT, the noise is only maybe 10 db. Not much if turned down low.
But turned up above "background" levels, the mush is hard to miss. It's not a "hiss" on first adjacents, it is more a "mush".

 

[Mike Walker]

It's the car radio in a 2006 Chevy Equinox. While it has very extended bass on AM, I'd guestimate the treble to take a nosedive above about 5khz. Still enough highs to keep sibilants clear, and speech intelligible, but you sure as hell don't get the "sizzle" from cymbals or trumpets.

My real test should be later this summer when WBT Charlotte becomes the first BIG SIGNAL AM in NC to go HD. That should reveal "I-Buzz" if there's any to be heard, and I should be able to hear it at my home...about 80 miles north of Charlotte...as WBT comes in just fine, and there's nothing on 1100, or 1120 in the daytime to cover up the sidebands.

 

[rbrucecarter5]

You don't suppose this has anything to do with your consitant recommendations of $9.99 Pocket Radios do you. Mix in a little selectivity. Mike is either lying, or maybe there's an equipment issue. Whadda YOU think??

Clouseau - read my post to Tom Ray. A VERY selective AM radio like the GE Superradio 1 mitigates IBOC somewhat. There is no audible self-jamming, and the high selectivity reduces, but not eliminates second adjacent hiss. First adjacent jamming, though, is even stronger.

Virtually all recent designs are wideband by nature - not out of any desire by the radio maker to deliver high fidelity. It is purely a cost cutting measure, and wide ceramic filters are cheaper than narrow ones, and eliminate select-in-test on the manufacturing line. One of my daughters radios was at least +/- 40 kHz bandwidth - cheap junk!!!!

 

[rbrucecarter5]

wait...if the presence of even a very weak signal completely covers "I-Buzz", well...

Counter point: I conducted a DX'pedition to a remote area recently. Very few AM stations on the dial at all. What astonished me, however, was the presence of IBOC sideband pairs - separated by 20 kHz - from stations hundreds of miles away. Stations that I could not even detect the analog audio from.

This has interesting implications, actually. The digital sidebands, if they are that robust, MAY increase coverage for very rural, isolated listeners in the Western 2/3 of the country. Provided, that is, that their receivers can decode the digital sideband pairs that I heard.

In areas where the band is NOT packed with stations, the sidebands are audibly much louder than the program content of the analog channel. Faint hiss from 300 mile distant WOAI is clearly audible on KFXR Dallas from my location during the day, and definitely covers 1210 kHz as well. Granted, 1210 is pretty weak in this area. Sideband hiss from KLIF 570 is annoyingly strong on KLBJ 590, which is strong enough in this area to be heard almost like a local. Sideband hiss from KLIF 570 also was clearly audible on Houston rimshot KLVI 560, and I was listening in GALVESTON, even farther from Dallas that Houston is. Analog KLIF audio was somewhat degraded at 300 miles, but its digital sidebands were vigorous.

This is not boding well for nighttime IBOC operation. If these digital sidebands are that robust during the daytime, I am concerned that at night they may propagate so well reception of any station will be impossible, unless you are a mile from the towers.

Something that I am very confused about, with digital sidebands this robust - why are HD listeners having trouble getting the things to decode????

 

[Mike Walker]

rbrucecarter5, you may be correct that the digital info being "that robust" might extend useful coverage. But I would guess (and it's only guessing) that the phase components in the digital info may become corrupt enough over great distances that it's possible to hear the sidebands on an analog radio, but still not decode HD. Again, only guessing.

 

[RememberWHEN]

I'm guessing here as well...but aren't the digital "sidebands" referenced to the analog signals carrier?? If that carrier is too weak then there is nothing to reference the digital information back to and the radio will not switch into digital mode. Kinda like sideband operation. Without the carrier you have no reference point and the demodulated audio is unintelligible. Restore to carrier and the sideband information has a reference point.

 

[Mike Walker]

Which is why all HD Radios have sync detection, I suppose RememberWHEN. They catch the carrier for a few seconds, phase lock onto it, and replace a fading carrier with a rock-solid, internally generated one.

 

[SUPERCASTER]

rbrucecarter5, you may be correct that the digital info being "that robust" might extend useful coverage. But I would guess (and it's only guessing) that the phase components in the digital info may become corrupt enough over great distances that it's possible to hear the sidebands on an analog radio, but still not decode HD. Again, only guessing.

I agree. HD radio is much more digital sizzle then useable signal.
Surprised, Mike?

HD radio does much more harm then good.

 

[Mike Walker]

Neither HD, nor any digital system is likely to provide solid, always-reliable signals through the meat-grinder of skywave...random phase shifts between carrier and sidebands, selective fading, etc. That doesn't mean HD is defective! It wasn't designed, and isn't a system for long distance (hundreds of miles) AM reception. I'm sure it will work sometimes, but certainly not reliably. Sadly (or not, depending on your perspective) the days of very long distance AM reception are coming to a close. Of course they'll never really go away as long as there's an analog component to terrestrial radio. Most don't care (about long-distance reception) anyway. I DO!

 

[SUPERCASTER]

Neither HD, nor any digital system is likely to provide solid, always-reliable signals through the meat-grinder of skywave...random phase shifts between carrier and sidebands, selective fading, etc. That doesn't mean HD is defective! It wasn't designed, and isn't a system for long distance (hundreds of miles) AM reception. I'm sure it will work sometimes, but certainly not reliably. Sadly (or not, depending on your perspective) the days of very long distance AM reception are coming to a close. Of course they'll never really go away as long as there's an analog component to terrestrial radio. Most don't care (about long-distance reception) anyway. I DO!

HD Interference immunity is a myth.

So this is progress?

Link to full story:
http://www.radio-info.com/smf/index.php/topic,73509.msg534779.html#msg534779

 

[Mike Walker]

My practical experience with HD extends ONLY to FM. Look at the Ibiquity map for North Carolina. I'm in the northwest corner of the state. We're 99.99999999 percent HD free (on AM) around here. I've heard only samples from the internet. You may be right. I have no freakin' idea. But I'm anxious to learn, by LISTENING with my own two ears (as I should be able to do when WBT goes HD this summer). Nobody's opinion will sway me. Only MY experience with MY ears!

 

[SUPERCASTER]

My practical experience with HD extends ONLY to FM. Look at the Ibiquity map for North Carolina. I'm in the northwest corner of the state. We're 99.99999999 percent HD free (on AM) around here. I've heard only samples from the internet. You may be right. I have no freakin' idea. But I'm anxious to learn, by LISTENING with my own two ears (as I should be able to do when WBT goes HD this summer). Nobody's opinion will sway me. Only MY experience with MY ears!

You can have it your way, Mike but as with the earlier audio clips you posted here, your ears have deceived you before.

 

[SUPERCASTER]

Neither HD, nor any digital system is likely to provide solid, always-reliable signals through the meat-grinder of skywave...random phase shifts between carrier and sidebands, selective fading, etc. That doesn't mean HD is defective! It wasn't designed, and isn't a system for long distance (hundreds of miles) AM reception. I'm sure it will work sometimes, but certainly not reliably. Sadly (or not, depending on your perspective) the days of very long distance AM reception are coming to a close. Of course they'll never really go away as long as there's an analog component to terrestrial radio. Most don't care (about long-distance reception) anyway. I DO!

HD Interference immunity is a myth.

So this is progress?

Link to full story:
http://www.radio-info.com/smf/index.php/topic,73509.msg534779.html#msg534779

All the locations mentioned in the above "Link to the full story" are within WPHT's 1210 AM (class A - old class 1a) 50 kw non-directional primary fulltime contour.
http://www.radio-locator.com/cgi-bin/pat?call=WPHT&service=AM&status=L&hours=U
From Radio-Locator:

The "local", "distant" and "fringe" lines on the AM maps corresponds to the predicted 2.5, 0.5, and 0.15 mV/m contours respectively (of the horizontal groundwave propogation only).

Link:
http://www.radio-locator.com/cgi-bin/page?p=maps

 

[Mike Walker]

My ears have never "deceived me". My hearing has been used as a test instrument at stations I've worked for. I'm a pain in the ass to chief engineers, but also a trusted "canary in the mine". If something's wrong, I HEAR IT. Almost always I'm the first to do so. No, my hearing acuity isn't any better than yours (probably). It may well be worse...more than 30 years of wearing headphones hours a day can do that to ya'! It's not about how well one hears, but how well they LISTEN!

My wife hears much better than I do (most women do). But I ALWAYS notice problems with reproduced sound before she does. It's my job, after all.

 

[R.F. Burns]

My ears have never "deceived me". My hearing has been used as a test instrument at stations I've worked for. I'm a pain in the ass to chief engineers, but also a trusted "canary in the mine". If something's wrong, I HEAR IT. Almost always I'm the first to do so. No, my hearing acuity isn't any better than yours (probably). It may well be worse...more than 30 years of wearing headphones hours a day can do that to ya'! It's not about how well one hears, but how well they LISTEN!

My wife hears much better than I do (most women do). But I ALWAYS notice problems with reproduced sound before she does. It's my job, after all.

Listening to noisy SWL stations and crowded ham bands for years teaches us how to listen. It's an excersize for lack of a better description.

 

[Mike Walker]

You're right, RF. Radio geeks learn to listen THROUGH noise, and we routinely listen to signals too damn noisy for the average person to put up with. I LOVE listening to distant stations, and just as with LP lovers, I am not bothered by the noise. But MY WIFE IS! I don't know how many times in the car, I've been listening to a distant AM station, and asked Robin "did you hear that?" "DID I HEAR WHAT?" she would ask..."all I hear is that damn noise. And it's driving me NUTS! Get a clear station, or turn that thing off!"