New NPR power calculator available (unofficially)

[briankay]

http://www.nprlabs.org/publications/distribution/interimIBOCpowerallowance/index2.php

Looks like a lot of stations will be able to turn up to the full -10 dBc even in the Chicago market. ;D Some can do the full -10dBc on only one of the sidebands. This could make some frequencies more valuable than other depending on how much they can their power.

At -10 dBc would be an enhancement to reception in a way -20 dBc never was. Of course that is if you have a HD radio. It would be nice hearing digital stereo for a change instead of picket fence analog mono in the peripheral areas near the 60dBu to 54dBu contours. It's probably already just a couple of dollars to add the HD radio chip in an in-dash receiver. So let's see if the auto manufacturers step up. They're probably the catalyst to get the change over to digital radio underway. They might well do it soon when they see more solid digital coverage but only if stations bump up to full digital power.

 

[BRNout]

There goes my reception of several Milwaukee market signals that I apparently have no right to enjoy!

The sooner this IBOC garbage hits the dustbin the better. It's getting out of hand with so much of the band compressed so that 0.3% of the audience can receive "HD" signals.

And, for the $64,000,000 question: how does all this play into the FCC's latest hobby of low power FM?

 

[tommygraser]

This is Great!!!! turn up the POWER baby I got my HD READY!!!!

 

[Play Freebird]

http://www.nprlabs.org/publications/distribution/interimIBOCpowerallowance/index2.php

Looks like a lot of stations will be able to turn up to the full -10 dBc even in the Chicago market. ;D Some can do the full -10dBc on only one of the sidebands. This could make some frequencies more valuable than other depending on how much they can their power.

Thanks for posting the link. The important number to keep in mind is the "D/U Ratio" in the second to last column in the second box. This represents digital-to-analog interference to each adjacent channel neighbor from the upper or lower IBOC sideband of the station under study. In reality, this is co-channel interference and cannot be eliminated through improvements in receiver selectivity.

For many years, FCC allocation standards have been based on a 20 dB co-channel D/U ratio, so a value less than 20 should be considered problematic. And if that number is low enough to be negative, expect a disaster.

For some examples of severe interference, here are several stations in the Northeast:

WKTU (which transmits from the Empire State Building); look at the effect on WPRB and WNNJ. There's plenty of population in those interference zones.

WDAS, Philadelphia vs WIOV

WUSL, Philadelphia vs WAWZ

But for that matter, WAWZ vs WUSL. (Hope they both remember Luke 6:31)

WENJ vs WPEN-FM

WAEB-FM vs WPPZ

WJFK (near Washington) vs WWMX and WWEG. Ugly!

Of course, grandfathered stations will also cause a lot of trouble. Check WTSS, Buffalo vs WLGZ, WVOR, and WNAE-FM.

Or, WNTQ, Syracuse vs WCIZ in Watertown. I also wonder about the impact on Canadian stations which apparently aren't taken into account here.

 

[Len14043]

It is interesting that on the initial NPR calculator, most or all of the stations in the east and midwest could not be increased beyond the current -20 db power level. With this new calculator, most of the stations can now raise their power up to -10db. Could someone explain what the information in the 2nd and 3rd column from the left means, i.e. F(50,10) dBu and D/U Ratio. I think the D/U ratio is the relationship between the IBOC sideband and the analog signal, but is that the ratio at the 40, 50 or 60 db contour?

 

[Play Freebird]

It is interesting that on the initial NPR calculator, most or all of the stations in the east and midwest could not be increased beyond the current -20 db power level. With this new calculator, most of the stations can now raise their power up to -10db. Could someone explain what the information in the 2nd and 3rd column from the left means, i.e. F(50,10) dBu and D/U Ratio. I think the D/U ratio is the relationship between the IBOC sideband and the analog signal, but is that the ratio at the 40, 50 or 60 db contour?

It appears that "F(50,10) dBu" refers to the predicted field strength of the IBAC digital sideband at the edge of the first-adjacent station's service contour. For a commercial Class B, the service contour is 54 dBu, for B1 it is 57 dBu, and for all other classes 60 dBu.

As I mentioned in my last post, the D/U Ratio (Desired analog / Undesired digital) provide the means to evaluate co-channel interference to the first-adjacent's analog signal; any number less than 20 represents a reduction in protection from normal FM allocation standards. If the number is negative, then the digital sideband would surpass the strength of the "protected" station's analog. Better receiver selectivity won't help in situations like this.

In the past, NAB made a big deal about similar proposals (for example, the Class A power increase to 6 kW) but they're obviously ignoring the negative impact of this change. However, to divert attention, you'll soon see a renewed fuss over the LPFM third-adjacent issue.

 

[briankay]

I think the D/U presented is the with reference to the main analog signal. As the digital power will be -10 dBc max, you can add 10 dB to that D/U ratio to get the co-channel interference amount. So if D/U is 10 dB in real terms it's 23 dB. The extra 3 dB takes account that the digital power is divided between the 2 sidebands. Each sideband having half the total digital power. So station at full digital power will be -13 dBc on each side band or in otherwords 5% of the analog power will be co-channel to the "victim" station if my rough understanding of this is correct.

The proof will be in the pudding though.

 

[Len14043]

Despite not being an engineer, I think I figured out the rationale behind the NPR calculator. A full -10 db power level would be permitted as long as the D/U ratio remains above +10. If the D/U ratio is less than +10 db, the allowable digital power is decreased incrementally until the -14 db level is reached, after which the protected station would not receive additional protection - even if the D/U ratio is less than zero.

 

[Play Freebird]

I think the D/U presented is the with reference to the main analog signal. As the digital power will be -10 dBc max, you can add 10 dB to that D/U ratio to get the co-channel interference amount. So if D/U is 10 dB in real terms it's 23 dB. The extra 3 dB takes account that the digital power is divided between the 2 sidebands. Each sideband having half the total digital power. So station at full digital power will be -13 dBc on each side band or in otherwords 5% of the analog power will be co-channel to the "victim" station if my rough understanding of this is correct.

The proof will be in the pudding though.

And if the pudding tastes like crap, will we all be forced to swallow it?

Out of curiosity, I started up my contour-plotting software and looked into this some more. Turns out that the D/U ratios shown in the NPR calculator are determined at the "victim" station's 60 dBu contour, regardless of class -- and as you suspected, they're based on analog power with no adjustments made for the specified IBOC injection level.

Taking WUSL, Philadelphia as an example, the F(50,10) analog interference contour at the edge of WRKS's 60 dBu service contour is 52 dBu. As you mentioned, assuming a nominal IBOC injection of -14, the lower sideband would be down another 3 dB; therefore, the predicted digital interference field strength (falling in WRKS's channel) is 35 dBu. So at the 60 dBu contour, WRKS would have a D/U ratio of 25 dB which should be adequate (except in the summer when "ducting" conditions exist many evenings.)

But at the WRKS 54 dBu contour (normally-protected service of a Class B commercial station) WUSL has an interference contour of 57 dBu. Subtracting 17 dB to adjust for digital injection, this works out to 40 dBu, leaving WRKS with a D/U ratio of only 14 dB on their analog channel. The normal protection requirement is 20 dB, so there will be a significant loss of service in these areas. To the listener, it will sound as if WRKS has decreased power.

WUSL's larger issue is the interference to WAWZ in Somerset County, NJ. At the edge of WAWZ's 60 dBu contour, WUSL has a 71.2 dBu interference contour. Subtract 17 dB from that and you get 54.2 dBu, leaving WAWZ with less than 6 dB D/U on their own channel. This will certainly result in a mutual increase in interference. At the WAWZ 54 dBu contour in Bucks County, PA the signal will be practically unusable on mobile receivers. Depending on local terrain, this may also affect WAWZ listeners in the NJ counties of Hunterdon and Mercer, well within the 60 dBu.

IBOC proponents will argue that these first-adjacent short spacings have existed for years and nobody has ever enjoyed full protection. However, ongoing improvements in receiver selectivity have really helped to resolve first-adjacent analog-to-analog spillover, particularly in car radios. Much of this effort is about to be negated, just as we've seen in the AM band.

A good slogan to keep in mind: With IBOC, first-adjacent is the new co-channel.

 

[Len14043]

Thanks for posting the link. The important number to keep in mind is the "D/U Ratio" in the second to last column in the second box. This represents digital-to-analog interference to each adjacent channel neighbor from the upper or lower IBOC sideband of the station under study. In reality, this is co-channel interference and cannot be eliminated through improvements in receiver selectivity.

For many years, FCC allocation standards have been based on a 20 dB co-channel D/U ratio, so a value less than 20 should be considered problematic. And if that number is low enough to be negative, expect a disaster.

Although the co-channel interference cannot be eliminated through improvement in selectivity, what about improvements in the capture ratio?

 

[SUPERCASTER]

This is Great!!!! turn up the POWER baby I got my HD internet radio READY!!!!

 

[Carmine5]

I've been reading a little more about asymmetrical sideband transmission for HD Radio and it made we wonder that if whole function of the second sideband is to provide redundancy and additional error correction why not eliminate that 2nd band entirely and simply beef up a single HD Radio band. As it is, reception of HD Radio is still unreliable despite the precaution of this extra band.

It seems to me that if they could forget the HD2/3 side channels, narrow the analog signal slightly, provide a minimum guard band and send a digital signal at a reasonable quality bit rate that would be close in strength to the analog signal, they could still fit it all within the 200 kHz bandwidth, including RDS information. Perhaps it could be modulated as a multiplex signal.

It just seems to me that the extra bandwidth real estate HD Radio is currently taking up is unnecessary.

c5

 

[SUPERCASTER]

I've been reading a little more about asymmetrical sideband transmission for HD Radio and it made we wonder that if whole function of the second sideband is to provide redundancy and additional error correction why not eliminate that 2nd band entirely and simply beef up a single HD Radio band. As it is, reception of HD Radio is still unreliable despite the precaution of this extra band.

It seems to me that if they could forget the HD2/3 side channels, narrow the analog signal slightly, provide a minimum guard band and send a digital signal at a reasonable quality bit rate that would be close in strength to the analog signal, they could still fit it all within the 200 kHz bandwidth, including RDS information. Perhaps it could be modulated as a multiplex signal.

It just seems to me that the extra bandwidth real estate HD Radio is currently taking up is unnecessary.

c5

I have not been able to find any definitive information about HD radio transmitting redundant digital sidebands. Perhaps it is one of their proprietary trade secrets. If that were the case, wouldn't the HD radio signals be much more reliable then they are?

If they are not redundant then a power disparity between the sidebands won't help HD radio reception much.

Regarding The rest of your proposal, it sounds similar to FMeXtra, a system which has existed for years.
With a minor change in the wording of the SCA rules and reprogramming of the Digital Signal Processor chips in future (and perhaps current) digital radios this service could almost immediately be available to the public.
With HD1 just a redundant (and perhaps unnecessary) exact duplication of the analog audio of the station, different programming (as now on HD2) could be provided. It has been reported by several engineers involved that FMeXtra reception is reliable within the primary coverage area of an FM station (unlike HD radio, which is not).
Links:
http://en.wikipedia.org/wiki/FMeXtra
http://www.vucastmedia.com/fmextra.html
http://www.rwonline.com/article/276

 

[SUPERCASTER]

Here are other links that I was not able to include in my post (above) because this board "timed out."
http://www.orban.com/about/press/release/2006_0424.php
http://www.youtube.com/watch?v=ZfPOe9VmDkE

 

[Carmine5]

I've been reading a little more about asymmetrical sideband transmission for HD Radio and it made we wonder that if whole function of the second sideband is to provide redundancy and additional error correction why not eliminate that 2nd band entirely and simply beef up a single HD Radio band. As it is, reception of HD Radio is still unreliable despite the precaution of this extra band.

It seems to me that if they could forget the HD2/3 side channels, narrow the analog signal slightly, provide a minimum guard band and send a digital signal at a reasonable quality bit rate that would be close in strength to the analog signal, they could still fit it all within the 200 kHz bandwidth, including RDS information. Perhaps it could be modulated as a multiplex signal.

It just seems to me that the extra bandwidth real estate HD Radio is currently taking up is unnecessary.

c5

I have not been able to find any definitive information about HD radio transmitting redundant digital sidebands. Perhaps it is one of their proprietary trade secrets. If that were the case, wouldn't the HD radio signals be much more reliable then they are?

If they are not redundant then a power disparity between the sidebands won't help HD radio reception much.

Regarding The rest of your proposal, it sounds similar to FMeXtra, a system which has existed for years.
With a minor change in the wording of the SCA rules and reprogramming of the Digital Signal Processor chips in future (and perhaps current) digital radios this service could almost immediately be available to the public.
With HD1 just a redundant (and perhaps unnecessary) exact duplication of the analog audio of the station, different programming (as now on HD2) could be provided. It has been reported by several engineers involved that FMeXtra reception is reliable within the primary coverage area of an FM station (unlike HD radio, which is not).
Links:
http://en.wikipedia.org/wiki/FMeXtra
http://www.vucastmedia.com/fmextra.html
http://www.rwonline.com/article/276

I guess I am describing FMeXtra. What prompted my thoughts on this was a sentence in this RW article:

http://www.radioworld.com/article/83748

"In theory, the idea of the double sidebands was to provide redundancy and more error correction."

Clearly this hasn't been entirely successful. So why not eliminate the 2nd band altogether and through a series of compromises, try to bring the hybrid signal into some kind of compliance within the FM mask. I would think that if they're talking about a power increase, confining the IBOC signal would be priority #1.

A key question would be how this would impact an analog radio's ability to receive this signal.

C5

 

[RadeoEngineer]

I think you have to look further into it in terms of cost to implement changes. Would the existing HD equipment be able to do this or would a station have to replace everything or at least some components of their existing HD chain. If it costs anything it's not likely to happen. Also, what about all those millions (just kidding Bob) of HD receivers already out in the field? Since none of them are to my knowledge field upgradeable, are they obsoleted?

 

[briankay]

I've been reading a little more about asymmetrical sideband transmission for HD Radio and it made we wonder that if whole function of the second sideband is to provide redundancy and additional error correction why not eliminate that 2nd band entirely and simply beef up a single HD Radio band. As it is, reception of HD Radio is still unreliable despite the precaution of this extra band.

It seems to me that if they could forget the HD2/3 side channels, narrow the analog signal slightly, provide a minimum guard band and send a digital signal at a reasonable quality bit rate that would be close in strength to the analog signal, they could still fit it all within the 200 kHz bandwidth, including RDS information. Perhaps it could be modulated as a multiplex signal.

It just seems to me that the extra bandwidth real estate HD Radio is currently taking up is unnecessary.

c5

Because of the redundancy of the 2 sidebands that's why 1 % power can cover as far as it does. Otherwise without the redundancy every bridge you go under would have silence. That's why the coverage is as good as it is going under bridges. Try stopping under a bridge and after about 4 seconds the digital is completely lost. The other reason for the 2 sidebands is that a first adjacent interferer my intermittentently affect one of the sidebands but 2 first adjacent interferers (one upper and one lower) are less likely to affect both upper and lower sidebands. But this can and does happen, which is why one station's digital coverage may be significantly less than the other when there are 2 strong 1st adjacent interferers. Try analog at the 1% level and see how bad the coverage would be. It's amazing that 1% digital does so well. Digital TV is at 20% of analog but doesn't need the double sideband redundancy as the receivers are not mobile (which would not work anyway due to the 8VSB signalling)

 

[SUPERCASTER]

briankay said:

Because of the redundancy of the 2 sidebands that's why 1 % power can cover as far as it does. Otherwise without the redundancy every bridge you go under would have silence. That's why the coverage is as good as it is going under bridges. Try stopping under a bridge and after about 4 seconds the digital is completely lost.

It seems you are loosing the HD signal as soon as you enter the tunnel and what you are hearing is the radio's built in 4 second buffer playing. Any radio with a 4 second buffer would do the same thing. This has nothing to do with the radio specifically being HD or redundant HD side channels. I believe Sirius/XM radios do the same when they loose a signal lock, and they are not HD radios.

Regarding your 1% HD power covering so very far, then why does HD radio need a power increase?
The relationship between power and coverage distance (assuming the same antenna height) is logaritmic, not linear. A 1% analog FM signal would probably cover about the same distance as HD radio.

Perhaps that's the answer to making HD FM and analog FM's coverage the same. Just require analog FM station's also transmitting HD signals to lower their analog power to 1%. Magically the HD and analog coverage areas are about the same, another problem is solved, power, money saved, co-channel interference to other stations reduced.

 

[Carmine5]

I've been reading a little more about asymmetrical sideband transmission for HD Radio and it made we wonder that if whole function of the second sideband is to provide redundancy and additional error correction why not eliminate that 2nd band entirely and simply beef up a single HD Radio band. As it is, reception of HD Radio is still unreliable despite the precaution of this extra band.

It seems to me that if they could forget the HD2/3 side channels, narrow the analog signal slightly, provide a minimum guard band and send a digital signal at a reasonable quality bit rate that would be close in strength to the analog signal, they could still fit it all within the 200 kHz bandwidth, including RDS information. Perhaps it could be modulated as a multiplex signal.

It just seems to me that the extra bandwidth real estate HD Radio is currently taking up is unnecessary.

c5

Because of the redundancy of the 2 sidebands that's why 1 % power can cover as far as it does. Otherwise without the redundancy every bridge you go under would have silence. That's why the coverage is as good as it is going under bridges. Try stopping under a bridge and after about 4 seconds the digital is completely lost. The other reason for the 2 sidebands is that a first adjacent interferer my intermittentently affect one of the sidebands but 2 first adjacent interferers (one upper and one lower) are less likely to affect both upper and lower sidebands. But this can and does happen, which is why one station's digital coverage may be significantly less than the other when there are 2 strong 1st adjacent interferers. Try analog at the 1% level and see how bad the coverage would be. It's amazing that 1% digital does so well. Digital TV is at 20% of analog but doesn't need the double sideband redundancy as the receivers are not mobile (which would not work anyway due to the 8VSB signalling)

It's interesting that you mention DTV because ATSC M/H (or Mobile TV) does use forward error correction which is incorporated into a single transport stream. This, in turn, is multiplexed with the legacy DTV signal and the entire transport stream is transmitted at the same ERP. And it does this all within the allotted 6 MHz bandwidth.

Too bad HD Radio doesn't use a similar approach.

c5

 

[briankay]

So will full HD reception will be possible while mobile? That's great news if so. Up to now all I've read is that mobile ATSC would have to use a portion of the main stream (thus reducing the bits available) and that only less than SD quality would be available for mobile devices, even if it's replicating the main program in the HD stream.

I haven't read the ATSC M/H spec but do you know if it just adds "intelligent" stream data to make almost the full 19.38Mbps recievable while mobile so it doesn't have to replicate streams. If the European type DTV system was adopted the need for a mobile standard would not have been necessary, right?

Also I believe IBOC on FM does use forward error correction "The channel encoding counteracts the normal RF transmission imperfections, which can include fading, interference and atmospheric noise. Forward error correction (FEC) adds correction bits to the pretransmitted signal with bit redundancy being used to improve system resistance to errors." http://radiomagonline.com/digital_radio/eye_iboc/radio_iboc_fm_waveform/