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Latest Tests on All Digital AM

C

Carmine5

RW had a brief article on the latest driving tests with all digital AM:

"The big takeaways are that the coverage of the all-digital AM signal “greatly exceeds” the hybrid AM HD Radio signal, said Layer. The all-digital AM HD Radio signal is also more robust than its hybrid counterpart.

NAB Labs also learned during the field tests that coverage is “highly dependent on co- and adjacent-channel interference” and nighttime performance “is an issue,” and needs to be investigated more thoroughly, according to Layer. “It’s unlikely a broadcaster would want to turn their analog off at night and replace it with this,” he said.

We’ve reported if the FCC authorized all-digital AM transmission, it would probably be for daytime use first."

- See more at: http://www.radioworld.com/article/a...ve-tests-complete/275551#sthash.KaAb5hXW.dpuf
 
tomservo said:
If it wasn't such a costly and sometimes complex upgrade for AM stations, it might be worth it to go all digital on an AM that's already being heard on a translator, that way you're alienating relatively few listeners.
Click to expand...

I think the potential is for coverage much greater than analog ever had, based on a drive test in remote stretches of Eastern NM - where sideband pairs from Chicago HD stations were clearly audible mid-day on separate occasions. No trace of carrier or analog, but it was pretty obvious what stations the sideband pairs were associated with. There were certainly no closer candidates. If I had reason to take a two day road trip, it would be interesting to go back to that remote location with my HD car radios and see if I could receive the Chicago stations. I can only think that pure digital would be much more robust.
 
While I am a proponent of all digital radio, the fact that digital AM "has issues" at night tells me that the technology isn't ready for primetime or maybe that the "Ratchett rule" will have to stay in place. Of course, this is using the Ibiquity system. I wonder if the problems would be the same with DRM?
 
These are my thoughts.
Successful implementation of all-digital radio on the present AM band has a major problem.
The static and other forms of noise which you can hear when listening to an analog AM station causes a digital receiver to become unlocked.
The result is total silence until the digital receiver can re-lock on the data stream.
For this reason, the digital coverage on medium wave frequencies will never approach the analog coverage (which remains audible ... even with a little static).
 
This article really sums up well the problems and unanswered questions with AM going digital:

"There’s no question someday the AM band will be all-digital, but unanswered is which system would be used, according to Hatfield & Dawson President Ben Dawson, noting that either the iBiquity technology, DRM or potentially a new system could be used. Some of his small market clients are adamant that they are never going to pay a private company, meaning iBiquity, “for the privilege of going digital,” according to Dawson.

CBS Radio SVP Engineering Glynn Walden said DRM would need to be vetted like HD Radio was, and that could take four to five years.

Panelists discussed the pros and cons of a receiver mandate to hasten digital receiver penetration in the market and what that figure should be before the industry pulled the trigger on all-digital AM. They also debated whether seeking a migration to television analog Channels 5 and 6 is really doable considering the upcoming television spectrum auction and subsequent repack. Thoughts were mixed on all questions."

- See more at: http://www.radioworld.com/article/l...re-all-digital-am/275597#sthash.HGP2akYo.dpuf
 
The article is selling snake oil. You may quote me on this: "Medium Wave (AM band) digital will fail."
 
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