TELECOM Digest OnLine - Sorted: Re: Article About AM Radio

Re: Article About AM Radio

Scott Dorsey (kludge@panix.com)
14 Mar 2006 11:26:06 -0500

John McHarry <jmcharry@comcast.net> wrote:

> IBOC is claimed to make AM sound like FM, but 36kb coded 15kHz audio
> is full of artifacts to a discerning ear. Mine isn't, but I worked
> with MP3 (a different coding scheme) with someone who is. We had to
> get that up to 128kb before he couldn't hear "flanging".

The worst part of AM IBOC is that it requires cranking down the
transmitted bandwidth of the analogue signal, AND it produces huge
amount of adjacent-channel interference.

The adjacent-channel interference has meant that many stations that
were audible through most of the US at night are no longer audible at
all. For the most part, I think skip is the single thing that makes
AM useful, and it when it is no longer possible to listen to distant
stations reliably, AM has no purpose to exist any more.

FM IBOC is much better designed and actually works. Not as well as Eureka,
but it's not horrible.

> The real push behind this is the transmission equipment manufacturers, and
> Ibiquity, who see a gold mine in the wholesale replacement of existing
> transmitters, and much upstream studio equipment.

Yes.

> The other pusher is large networks of FM stations, including Clear
> Channel, but perhaps more so, NPR. FM IBOC can be subdivided into
> multiple channels, allowing a single station licensee to serve two or
> three market segments. This is being tested on air as we "speak". The
> scuttlebutt is that it works acceptably, although my golden eared
> friend would probably yodel his lunch. My guess is that if, and it is
> a big if, IBOC catches on, there will not be an increase in audio
> quality, but in quantity. And that is a reaction to the competition
> from satellite radio.

I'm not sure multicasting will really mean much. If you look in a
major market, you see dozens of stations that all are playing the same
music. Adding multicast IBOC signals will double the number of
stations playing the same music. This is not an improvement.

--scott

"C'est un Nagra. C'est suisse, et tres, tres precis."

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