RW: All-Digital AM Test On The Way

[iyiyi]

CBS still uses WBCN for web sites in Boston. WBCN was a legendary rock station and CBS wanted to park the call letters.

WBCN was a key set of call letters that launched FM radio into the stratosphere. Great calls to move HD radio to the next level!

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[JohnnyElectron]

If I'm not mistaken, all HD radio chipsets to date are able to receive an all-digital AM-HD or FM-HD signal in addition to hybrid analog/digital?
Am I correct in my assumption?

 

[RL]

If the data carrier is moved to the center it will work.
Data only need be above noise to be detected.
I asked for this in 1997.
If you ever wanted your own station, this is an opportunity to make a difference.

 

[rbrucecarter5]

If the data carrier is moved to the center it will work.
Data only need be above noise to be detected.
I asked for this in 1997.
If you ever wanted your own station, this is an opportunity to make a difference.

Which is also why I think FM stations merely moving their sidebands in towards the center will work with no modification to HD radios whatsoever, but will result in immediate coverage gains for HD FM. And probably fix the coverage situation with analog, because the sidebands will no longer fool the AGC into thinking there are adjacent noise signals.

 

[cd637299]

Seriously, isn't this like adding a GPS, iPod, anti-lock brakes, etc., on a Model T?

cd

 

[mmnassour]

A Model T could benefit from all three of those. There's no benefit to this.....experiment.

 

[diymedia]

If I am not mistaken:

On FM in all-digital HD mode, the analog portion of the signal is replaced with digital capacity, though the overall spectral footprint of the signal does not change. In fact, the sidebands are apparently still broadcast at a higher power level than the center portion - the diagram looks like RF-walls to protect the middle space.

On AM, all-HD drops the spectral footprint of a station from 30 KHz to 20 KHz.

 

[iyiyi]

The farther that signals get from the center frequency, the more susceptable they are to phase and amplitude interferences (multipath, skywave, QRM etc.). Increasing sideband amplitude is one way to help offset these problems.

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[rbrucecarter5]

The farther that signals get from the center frequency, the more susceptable they are to phase and amplitude interferences (multipath, skywave, QRM etc.). Increasing sideband amplitude is one way to help offset these problems.

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So is moving them in towards the center. There is no secondary service above the multiplex portion of the signal that cannot be done better by HD radio. Lets at least give HD radio a chance by improving its reception. Why prop up dinosaurs like RDS, SCA, etc and put HD radio at risk? Moving the sidebands in corrects a multitude of problems and gives HD a fighting chance.

 

[JohnnyElectron]

rbruce, how can you get the sidebands moved-in? Is that strictly an iBiquity programming fix?

 

[iyiyi]

The farther that signals get from the center frequency, the more susceptable they are to phase and amplitude interferences (multipath, skywave, QRM etc.). Increasing sideband amplitude is one way to help offset these problems.

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So is moving them in towards the center. There is no secondary service above the multiplex portion of the signal that cannot be done better by HD radio. Lets at least give HD radio a chance by improving its reception. Why prop up dinosaurs like RDS, SCA, etc and put HD radio at risk? Moving the sidebands in corrects a multitude of problems and gives HD a fighting chance.

I understand where you are coming from now. An FM channel is 200 kHz wide. 100% modulation is +/- 75 kHz deviation from the center frequency. There are 25 kHz "guard bands" on each side of center that fill out the remaining 50 kHz of the channel.

Here's what happens. A mono FM signal at 100% mod will deviate +/- 75 kHz maximum from center frequency. A stereo FM signal at 100% mod will deviate +/- 75 kHz from center frequency. The difference? Mono is broadcast as an entire signal. Stereo must devote 10% mod for the 19 kHz pilot, 45% mod for the L+R and 45% mod for the 23-53 kHz (38 kHz center) L-R at 100% modulation. Now we'll add RBDS, 67 and 92 kHz to the mix. 100% modulation is still +/- 75 kHz from the center frequency. It now consists of 10% mod for 19 kHz pilot, 5% mod for RBDS info, 10% mod for 67 kHz SCA, 10% mod for the 92 kHz SCA, 32.5% mod for the L+R and 32.5% mod for the L-R info to account for the 100% modulation.

Audio amplitude in FM is determined by the amount of deviation from center frequency. Audio frequency in FM is determined by the rate the signal swings through the center frequency. NRSC-5-C figure 20 clearly shows the 200kHz analog FM region totally protected from HD IBOC interference. NRSC-5-C figure 21 shows a proper IBOC signal when unencumbered by analog constraints. Therefore you cannot move the FM digital IBOC sidebands in without adversely affecting the significant sidebands of the analog signal!

NRSC-5-C figures 9 - 12 demonstrate HOW and WHY MW IBOC sidebands are easily moved in by simply limiting the highest analog audio frequencies to create more free space.

An FM IBOC in hybrid mode is fully capable of delivering 100% analog modulation in any configuration of mono, stereo, RBDS or SCA that a non HD analog FM can do.

A MW HD IBOC station is fully capable of delivering an analog high quality, albeit mono, 8 kHz audio signal at 100% modulation.

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[KB1OKL]

CBS still uses WBCN for web sites in Boston. WBCN was a legendary rock station and CBS wanted to park the call letters.

WBCN was a great station, the jocks on that station were like your buddies, Mark, Charles, Ken, even Matt Segal at one time, Duane Ingalls Glascock, they were talking to you. I had that station on everywhere I could receive it.

 

[rbrucecarter5]

Therefore you cannot move the FM digital IBOC sidebands in without adversely affecting the significant sidebands of the analog signal!

Unfortunate - still more proof that it was badly engineered from the start, not to be flexible enough to make changes if problems arose. The unreliability is a show stopper with consumers. Even someone like me, used to reception problems on distant stations - gets tired of extended HD dropouts. At least if the signal gets some static you can still hear something. HD-2 goes completely silent. The one and only killer app of the system, and there is no graceful degradation path that still allows audio.

Here is a thought - as talk radio abandons AM for FM and HD sub-channels, maybe FM music stations can put their HD-2 on the AM frequencies vacated. A little software change, and the radio can tune to the AM version of HD-2 when the HD drops ---- possible or another tangent? I just don't see anybody who will tolerate dropouts on HD-2, especially when the regular analog / HD-1 is totally uninteresting.

 

[JohnnyElectron]

You get points for thinking outside of the box there rbruce - the HD2 on a matching AM frequency as a temporary fall-back upon FM-HD2 signal loss is a great idea; sort of like the 'remapping' HDTV does to tell you that your TV36 is really on RF49.
I'm like you; I'll take a little bit of static and noise rather than zero audio for 5 seconds. Even AM (with bad AGC) going under an overpass is only 2 seconds of reduced audio.

That's even true for the digital police scanners here - you get some audio or nothing at all - not a very safe use of digital for public service forces, in my opinion. But back to topic; an alternate ANALOG frequency for HD2/HD3 LOS is a great idea - just need to keep the timing matched.

 

[xmtrland]

Back to the original thought of this digital only AM station. Wonder since it's getting so close, think they will play Christmas music? Would make sense, it would be short term format change that many stations do this time of year. Small market they could give away a few radio to businesses around town to play the Christmas music.

Someone from Ibiquity could dress up as Santa Clause, this could be a great promotion with Santa Ibiquity giving away HD Radios to all the good little boys in girls. Better yet call him Ibiquity Clause.

Next year they could take it National.....Yes this could indeed be the salvation of HD Radio.

Editorial note: I did not hit my head in the shower today.

 

[xmtrland]

Ok bad spelling error, should read above "boys and girls" oops

 

[stacker]

Someone from Ibiquity could dress up as Santa Clause, this could be a great promotion with Santa Ibiquity giving away HD Radios to all the good little boys in girls. Better yet call him Ibiquity Clause.

Priceless! Thanks for the laugh.

 

[pianoplayer88key]

Even better is the editorial note at the end of the post. ;D (I will kindly overlook the "hidden meaning" in the so-called "spelling error". )

 

[Mike Sheridan]

When does this "Digital Only" test begin?

 

[Carmine5]

There is an interesting entry in the DIYMedia blog decrying the secrecy surrounding the scheduled test of all digital HD-AM (actually its a series of three or four tests involving several AM stations).

As the author points out there has been a consistent lack of transparency in the testing of new technology for the radio industry. For HD Radio, as an example, a small but powerful cabal of radio companies tested the system, presented their findings before the FCC and the Commission adopted it without, apparently, any thought as to how this would affect smaller independent stations or the industry as a whole.

To quote:

"As the record shows, this lack of transparency during HD's development poisoned the policymaking environment and trade press. There was massive consternation among independent (i.e., non-iBiquity investor) broadcasters and the public about HD's fundamental viability, not to mention its profound effects on the future potentiality of digital radio broadcasting itself. However, by that point the FCC had already effectively made up its mind on HD by opting out of any active role in the technology's development and plans for rollout."

So the secrecy surrounding the AM station lucky enough to get this all-digital test is just part of a larger, long-standing pattern.

http://www.diymedia.net/