Isn't it time to demand DRM for AM?

[OKCRadioGuy]

Since most of these "HD" radios are software-driven anyway, wouldn't it be smart for us, as an industry to demand that all "HD" radios from this point on also get DRM on the AM band? After enough radios get out into the market, some stations could just go DRM and leave the crappy analog behind at their own choosing. Folks, we're painting ourselves in one HELL of a corner by exclusively accepting the IBOC standard on AM where, from what I understand, we CAN'T run digital only. IBOC doesn't have the range, interfers with others on the adjacent channels, and requires a LOT more bandwidth abilities of an array to make it work. Let's get this message up to someone that can help set the rules up to get DRM out into the public's hands before it's too late and we're stuck with inferior technology forever.

 

[R.F. Burns]

Since most of these "HD" radios are software-driven anyway, wouldn't it be smart for us, as an industry to demand that all "HD" radios from this point on also get DRM on the AM band? After enough radios get out into the market, some stations could just go DRM and leave the crappy analog behind at their own choosing. Folks, we're painting ourselves in one HELL of a corner by exclusively accepting the IBOC standard on AM where, from what I understand, we CAN'T run digital only. IBOC doesn't have the range, interfers with others on the adjacent channels, and requires a LOT more bandwidth abilities of an array to make it work. Let's get this message up to someone that can help set the rules up to get DRM out into the public's hands before it's too late and we're stuck with inferior technology forever.

OK good question. First the issue is that DRM isn't compatible with analogue transmission. Unless a station can broadcast both simultaniously they will lose a good portion of the available audience. There is no free spectrum for a transplant so whatever system finally wins oout it must be analogue compatible. I don't know where you go the idea that the analogue component can never be shut down for IBOC to run properly. the whole idea is to eventually turn off the analogue carrier and run exclusively IBOC digital. When the analogue gose away they should be able to increase the bit rate and improve the audio of the AM audio. The whole coverage issue is a non issue actually. Today the IBOC part of the system is being run at reduced power, which is one reason for the reduced coverage. Also, many of the anti IBOC proponents claim that IBOC's coverage is poor based on a single first generation, problem receiver. It would be like judgng all automobiles based on the Ford Pinto's exploading gas tank. While I am not thrilled with IBOC on AM due to the current low bitrate audio, what I've found is that most of the annoying artifacts can be reduced by audio tayloring. Also, in the noisy automobile environment most of that detail is lost anyway. At least at this time, only the radio can provide instant information live to a listener in an automobile. Cell phones are illegal to use in the car, unless you are using a hands free device and hands free would mean choosing a specific program and not touching the cell phone until you have parked and turned off your car. Not only does it get expensive, it's not very flexible. As for Wi-Fi, I want to know what the weather is going to be like this afternoon, not 10 years from now and until all the technical obsticles which a wi-fi system will present, wi-fi on a wide scale is not a viable alternative. This is 2007 not 2017. Most radio listeners are not home bound. Most are highly mobile and it's that need which must be met. At this time there are no free alternatives to our current radio system.

 

[OKCRadioGuy]

Good points. From what I have heard here and there IBOC or should I say IBAC cannot be ran in the purely digital mode. (AM I wrong? I'd like to see some info on this) That's a serious flaw for the future 2017, so to speak. I'm not saying everyone should totally abandon IBOC for AM in hybrid mode for now. (although I would if I owned a station!! The cost and problems vs. the value just isn't there) What I'm saying is we need to figure out how to make sure we aren't screwing ourselves in the future WHEN there are enough radios out there. DRM is good proven technology that actually works very well with very little signal. Europe is currently using it on shortwave with great success really. Why not ask to have radios that can receive it along with IBOC?

 

[PhilJSmith67]

From what I have heard here and there IBOC or should I say IBAC cannot be ran in the purely digital mode. (AM I wrong? I'd like to see some info on this)

Yes, that is incorrect. The technical specification for iBiquity's HD Radio supports hybrid and all-digital modes. This spec is on file with the FCC. http://hraunfoss.fcc.gov/edocs_public/attachmatch/FCC-02-286A3.pdf The JVC receiver I tried mentioned all-digital AM and FM capability in the manual, too.

With the hybrid signal, the primary, secondary and tertiary ensembles are all transmitted as mirrored sidebands above and below the center carrier. The all-digital signal mirrors only the primary ensemble as sidebands nearest the center carrier. The secondary ensemble is transmitted immediately above the upper primary sideband, and the tertiary on the opposite side, immediately below the lower primary sideband.

The all-digital HD Radio signal is more effecient, with the higher-powered primary sideband staying within a span of 9.8 kHz (4.9 kHz below and above carrier), but adding the lower-powered secondary and tertiary sidebands makes the all-digital signal span 18.9 kHz. It's a still a bit wide, but much better than the 29.5 kHz of real estate needed for a hybrid HD Radio signal, of which the higher-powered primary sidebands are flapping away at 10 to 15 kHz from the center carrier.

Can DRM operate within a 10 kHz-wide channel, or does it also take a bite out of adjacent channels?

 

[OKCRadioGuy]

From all I've seen DRM it will stay within the 10. At least we'll have something to look foward to if we can at least go all digital in the future and dump the hybrid mode at some point. I still don't think the wider usage of bandwidth is a very good thing, but at least it's better. Frankly FM is going to either drive the sales of IBOC radios (or not). Hopefully AM will get some benifits further down the road.


Thanks for the info.