All-Digital AM Test Data Continues to Look Positive

Results of all-digital AM testing continue to look positive, and NAB Labs is charting a path to eventually asking the FCC for authorization in the event that U.S. broadcasters decide they want to do that.

So said NAB Senior Director of Advanced Engineering David Layer during a Broadcast Engineering Conference session here at the NAB Show in Las Vegas.

The most recent testing involved Greater Media’s WBT(AM), Charlotte, N.C.; Cumulus-owned KTUC(AM), Tuscon, Ariz.; and WD2XXM, an iBiquity test station in Frederick, Md. All of these were already transmitting hybrid digital signals.

NAB Labs is using consumer receivers to characterize the all-digital coverage.

Cumulus SVP Engineering & IT Gary Kline said the all-digital audio sounded “far better than I expected.” He said he walked away from the tests “feeling pretty good about running all-digital HD on AM.”

Greater Media VP of Radio Engineering Milford Smith said the all-digital AM HD Radio signal on the 50 kW clear channel WBT “was very robust.” This was a second round of testing on WBT, to eliminate anomalies found in round one.

The Labs has now conducted drive tests on five AMs and hopes to test on another four facilities in 2014. Cavell and Mertz is developing a lab test facility that eventually will be located at NAB Labs; the point is to develop repeatable tests that back-up the drive data.

Smith told Radio World the NRSC this weekend discussed the possibility of eventually evaluating all-digital AM, similar to tests that members conducted before what was then called IBOC was authorized by the commission.

All HD Radio receivers in the field today can receive an all-digital signal, according to panel participants.
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Comment List:

One thing about Digital Radio Mondiale that stations would look at, can the station play music in stereo using that system? DRM does not support stereo, while Ibiquity's system does. I've listened to HD AM, and it has some merit. Going all-digital on AM, while an interesting idea, would probably be a mistake. People depend on AM radio in times of emergency. AM can reach out farther than any FM station can. Groundwave has the advantage of following the curvature of the earth, while FM is only line of sight. I don't think AM is going anywhere for a long time to come. Going all-digital would not be good. Despite claims otherwise, AM has not lost its usefulness. Do we need digital AM? No. Supplement, sure, but don't replace.
By Jay Rudko on 3/29/2015
I have to agree with the comments here, thus far. This dog won't hunt. I have one of the Sony "HD" radios that was given the highest ratings... and it REALLY struggles, even with 20mv signals. Once the sun starts to set... it's all over, Baby. May as well make those proposed "all digital" 50Kw stations all Daytimers... and give them true "Clear Channel" status. Good luck with that. Oh.. yeah, where are the radios? "Bricking" hundreds of millions of good radios is NOT going to go well with John and Jane Q. Public.
By Willie... on 6/8/2014
Rather than saving AM radio - "bricking" hundreds of millions of existing radios will spell the death of AM. HD has failed to capture consumer appeal. Time to stick a fork in it, its done. It's dead, Jim!
By Bruce Carter on 4/8/2014
Stop being hore's to iBiquity ! These are PUBLIC airwaves... if you must push "go digital" then use an open standard like Digital radio Mondiale. My suggestion is to remove all the 'digital' IBOC crap and broadcast clean Amplitude Modulation! But who am I to say..I'm just a dumbass engineer.........
By Jerry Goodell on 4/8/2014
"All-Digital AM Test Data Continues to Look Positive": this is non sense. Digital is not only Amplitude Modulated. "All digital MW" is the correct way. Also, MW band is prone to interferencies...and digital HATE interferencies. I agrre with "Cranky Old Man" arguments.
By Jose Claudio Barbedo on 4/7/2014
FM and Digital are for sissies...if it doesn't SNAP, CRACKEL, or POP, it AIN'T Radio.
By I'm cranky too. on 4/7/2014
I think that statement just summed-up the robustness of an all-digital AM band in the USA: " eliminate anomalies found in round one..." - yeah, like the part where the digital audio takes 10 seconds to recover after a static crash and only 1/2 second when it's an all analog signal? In my opinion, an all digital MW/AM band is about on par with filling the Goodyear Blimp with hydrogen gas and running a 1KW CW transmitter on-board the craft. All digital transmissions might work wonders on VHF, but I just do not see iBiquity's AM system working below 30MHz on anything less than a 50KW single-tower 1A omnidirectional AM station - even then, static crashes are still its Kryptonite.
By Cranky Old Man on 4/7/2014

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