Nighttime AM IBOC

[Len14043]

I am generally an IBOC supporter and hope that the technology takes off. I believe the system works as intended for FM, as well as daytime AM. However, intuitivly, I see serious problems for nighttime IBOC. I'm not referring to the interference it is alleged to cause, but strictly on how it will perform. WLW can be received in HD to about 90 miles from their tower. But how will WLW do when the skywave comes in on 690 and 710? On nights when the skip is good, I can can hear stations on 690 and 710 within 10 miles of the WLW tower. Does this mean that WLW's nighttime digital signal could be constricted to 20 miles due to the distant stations overriding their digital sidebands? I am curious on how a 1000 watt station on 1240 would fare with digital sidebands of only 10 watts. It is doubtful that a digital signal could be heard over 2-3 miles in that environment, seeing that the skip on graveyard frequencies could be 10 mv/m. I have no doubt that AM HD will be viable in the all-digital mode, but currently have serious doubts about the hybrid mode at night.

 

[IBOCRocks]

I am generally an IBOC supporter and hope that the technology takes off. I believe the system works as intended for FM, as well as daytime AM. However, intuitivly, I see serious problems for nighttime IBOC. I'm not referring interference it is alleged to cause, but strictly on how it will perform. WLW can be received in HD to about 90 miles from their tower. But how will WLW do when the skywave comes in on 690 and 710? On nights when the skip is good, I cam can hear stations on 690 and 710 within 10 miles of the WLW tower. Does this mean that WLW's nighttime digital signal could be constricted to 20 miles due to the distant stations overriding their digital sidebands? I am curious on how a 1000 watt station on 1240 would fare with digital sidebands of only 10 watts. It is doubtful that a digital signal could be heard over 2-3 miles in that environment, seeing that the skip on graveyard frequencies could be 10 mv/m. I have no doubt that AM HD will be viable in the all-digital mode, but currently have serious doubts about the hybrid mode at night.

I agree. I would like to see a closer look taken at nighttime operation on AM. I am a major FM IBOC supporter, but I'm not as gung-ho about AM, even though it sounds great!

 

[SayNoToIBOC]

This article summarizes the problems with AM IBOC, in general:

http://www.wbdhradio.com/html/say_no_to_iboc.html

 

[audiophile.]

Anybody that has any experience with DTV knows that even the low VHF channels are bad because of co-channel interference. How they expect this system to work on AM at night is beyond me. The only digital solution for night time is digital only +/- 5 kHz on center channel (much like DRM) or analog only. Let the broadcasters choose the mode at their option.

PS has IBOC been tested on AM in digital only mode? Will the recievers work/compatible in this mode? (for that matter what about the FM receivers?)

 

[Chuck]

Anybody that has any experience with DTV knows that even the low VHF channels are bad because of co-channel interference. How they expect this system to work on AM at night is beyond me. The only digital solution for night time is digital only +/- 5 kHz on center channel (much like DRM) or analog only. Let the broadcasters choose the mode at their option.

PS has IBOC been tested on AM in digital only mode? Will the recievers work/compatible in this mode? (for that matter what about the FM receivers?)

For that matter, would "digital only" signals be limited to 1/100 of the authorized analog signal? I don't know if that has been addressed. If a station had a 100 watt night authorization, I doubt that a 1 watt digital signal would be very effective, but a 100 watt all digital signal might be a real improvement for many stations.

I can't see many night operating AM's giving up their analog signal right now, but if enough radios get out there, they might actually be willing to try it. Time will tell, I guess.

 

[rbrucecarter5]

The nature of the digital sidebands is such that even at low transmitted power, they can be received as well or better than the main channel. I have heard the digital sidebands of KOA as far south as Dumas, TX, and they were louder than KOA's main channel. Same with the sidebands of KMKI 620 Dallas - I can hear the lower sideband strongly in Lubbock, TX, and the upper sideband produces noticable noise on a nearby 630. The lower sideband is louder than the analog audio. When WOAI fires up IBOC, the upper sideband can be heard on 1210 - long after the analog signal is covered up by adjacent 1190. Sometimes the upper sideband persists into mid morning.

None of this bodes well for nighttime IBOC. When thousands of stations fire up digital sidebands, it will amount to broadband jamming of the band.

 

[Chuck]

The nature of the digital sidebands is such that even at low transmitted power, they can be received as well or better than the main channel. I have heard the digital sidebands of KOA as far south as Dumas, TX, and they were louder than KOA's main channel. Same with the sidebands of KMKI 620 Dallas - I can hear the lower sideband strongly in Lubbock, TX, and the upper sideband produces noticable noise on a nearby 630. The lower sideband is louder than the analog audio. When WOAI fires up IBOC, the upper sideband can be heard on 1210 - long after the analog signal is covered up by adjacent 1190. Sometimes the upper sideband persists into mid morning.

None of this bodes well for nighttime IBOC. When thousands of stations fire up digital sidebands, it will amount to broadband jamming of the band.

Where I live in East Texas, about 140 miles from Dallas, I can hear KRLD's (AM) sidebands louder than their main 1080 signal. For a hybrid system, I think there is a real problem for nighttime AM IBOC. On the other hand, if you could do an all-digital night signal at your full power, that might be a different story. That probably means using a different system though, like DRM. Or, can the Ibiquity system be modified to stay in band for a digital only broadcast? Although digital only, DRM at least keeps in the assigned band so night time interference issues shouldn't be any worse than they already are.

I guess that idea makes more of a case for manufacturers offering digital receivers that are capable of several demodulation methods. The Ibiquity folks won't like it, but I think that is what it will take to get it to fly. There is no free lunch. They do it with HDTV's and it is invisible to the viewer. Since all the competing digital AM systems are software based (albeit with specific pre programmed chip sets) there is not much technical reason why the chips couldn't be pre-programmed to decode different systems.

 

[rbrucecarter5]

Where I live in East Texas, about 140 miles from Dallas, I can hear KRLD's (AM) sidebands louder than their main 1080 signal. For a hybrid system, I think there is a real problem for nighttime AM IBOC. On the other hand, if you could do an all-digital night signal at your full power, that might be a different story.

I am not surprised - it finishes reception of KNX when they fire up those sidebands. I suspect not just for Dallas, but for many locations much closer to LA that are still in darkness at the time.

The nature of digital transmission concerns me. I believe the harmonics generated by it would go up and down the spectrum. It may well be that the best answer is Ibiquity day and C-Quam night.

 

[SayNoToIBOC]

I think the best solution is just to leave analog AM/FM alone - digital radio isn't gaining us anything, but better programming would...

 

[Len14043]

RBRUCECARTER5 WROTE: The nature of digital transmission concerns me. I believe the harmonics generated by it would go up and down the spectrum. It may well be that the best answer is Ibiquity day and C-Quam night.

Bruce, glad to see you made it over to this board. I used to read your posts before this board underwent a format change. Concerning C-Quam, my understanding is that C-Quam is a wide-band analog system. If that is the case, wouldn't that cause problems similar to that of IBOC at night, i.e. material outside the main channel interfereing with other stations?
I hope the FCC continues to disallow AM nighttime hybrid IBOC into the forseeable future, but allow full digital at night. At least stations would continue to broadcast within their assigned channel. Hopefully, if FM IBOC reaches critical mass, and radios continue to provide digital capabilities for AM, some pioneering broadcasters will take a risk and start broadcasting in the all-digital mode. I realize there my be other solutions, but I believe the aim of the FCC should be to encourage an all-digital mode as soon as practicable. For that matter, I think FM would be better off in the all-digital mode.

 

[vsa]

Don't forget about CAM-D --- compatible AM digital.
Better analog coverage and no new interference.

Contrary to what some may say, it is far from dead. It's the new and true IBOC for AM. Just my 2 cents.

http://www.wrathofkahn.org/wst_page5.html

 

[zumahans]

RBRUCECARTER5 WROTE: The nature of digital transmission concerns me. I believe the harmonics generated by it would go up and down the spectrum. It may well be that the best answer is Ibiquity day and C-Quam night.

Bruce, glad to see you made it over to this board. I used to read your posts before this board underwent a format change. Concerning C-Quam, my understanding is that C-Quam is a wide-band analog system. If that is the case, wouldn't that cause problems similar to that of IBOC at night, i.e. material outside the main channel interfereing with other stations?
I hope the FCC continues to disallow AM nighttime hybrid IBOC into the forseeable future, but allow full digital at night. At least stations would continue to broadcast within their assigned channel. Hopefully, if FM IBOC reaches critical mass, and radios continue to provide digital capabilities for AM, some pioneering broadcasters will take a risk and start broadcasting in the all-digital mode. I realize there my be other solutions, but I believe the aim of the FCC should be to encourage an all-digital mode as soon as practicable. For that matter, I think FM would be better off in the all-digital mode.

All digital AM ?

Are you serious?

Not in your lifetime.

 

[IBOCRocks]

RBRUCECARTER5 WROTE: The nature of digital transmission concerns me. I believe the harmonics generated by it would go up and down the spectrum. It may well be that the best answer is Ibiquity day and C-Quam night.

Bruce, glad to see you made it over to this board. I used to read your posts before this board underwent a format change. Concerning C-Quam, my understanding is that C-Quam is a wide-band analog system. If that is the case, wouldn't that cause problems similar to that of IBOC at night, i.e. material outside the main channel interfereing with other stations?
I hope the FCC continues to disallow AM nighttime hybrid IBOC into the forseeable future, but allow full digital at night. At least stations would continue to broadcast within their assigned channel. Hopefully, if FM IBOC reaches critical mass, and radios continue to provide digital capabilities for AM, some pioneering broadcasters will take a risk and start broadcasting in the all-digital mode. I realize there my be other solutions, but I believe the aim of the FCC should be to encourage an all-digital mode as soon as practicable. For that matter, I think FM would be better off in the all-digital mode.

All digital AM ?

Are you serious?

Not in your lifetime.

Unlikely, but not impossible.

 

[zumahans]

Not even the rosiest broadcast apologist can say that.

AM Stereo was compatible with existing radios and look how compelling that was to the market.

IBOC rocks, yeah, right.

 

[IBOCRocks]

Not even the rosiest broadcast apologist can say that.

AM Stereo was compatible with existing radios and look how compelling that was to the market.

IBOC rocks, yeah, right.

Oh, here we go again. Comparing AM Stereo to IBOC. Search back through the threads, we've all been through THAT discussion three or four times. They aren't even close.

 

[zumahans]

Oh, here we go again. Comparing AM Stereo to IBOC. Search back through the threads, we've all been through THAT discussion three or four times. They aren't even close.

Yeah, AM stereo had higher audience acceptance.

 

[IBOCRocks]

Oh, here we go again. Comparing AM Stereo to IBOC. Search back through the threads, we've all been through THAT discussion three or four times. They aren't even close.

Yeah, AM stereo had higher audience acceptance.

Right, AM stereo was huge. Oh wait, no it wasn't! There were several standards, and by the time the FCC decided, it was much too late.

Fortunately the lesson was learned from that debacle.

I love the AM stereo references. It's usually the first argument someone throws up. They get schooled pretty quick after that.

 

[zumahans]

I love the AM stereo references. It's usually the first argument someone throws up. They get schooled pretty quick after that.

Having read your posts here, I would estimate that schooling to be at about the sixth grade level.

 

[IBOCRocks]

I love the AM stereo references. It's usually the first argument someone throws up. They get schooled pretty quick after that.

Having read your posts here, I would estimate that schooling to be at about the sixth grade level.

Wow...another good one. Will you be presenting any facts today, or just hurling insults like a grade-schooler at recess?

 

[I.B. Iquity]

Mt question is how does he remember all the different passwords for each of the names he's using?