I'm curious about how and why anyone proposes to transmit digitalized
audio in the standard A.M. broadcast band, which in the U.S. is divided into
10-kilohertz channels (9 kHz in Europe). The FM broadcast band, with
200-kHz channels would be far more suitable. But, of course, FM sound is
already pretty good because its audio spectrum extends up to 20 kHz as
compared with 5 kHz for the A.M. broadcast band. The 10:1 ratio of FM
bandwidth to audio bandwidth gives this "wideband FM" a correspondingly
improved output signal-to-noise ratio when the input SNR is high--and a
corresponding deterioriation when it's not.
Whatever way the AM band with 10-kHz channels may be used for digital
audio, it will likely suffer the same sort of deterioration at low SNRs. It
may thus be useful only in metropolitan areas, just like FM despite the
nighttime ionospheric reflections, which greatly extend the A.M. range after
dark.
I suspect the radio industry is simply trying to make all radios obsolete
as fast as possible just as the TV industry is pushing high-definition TV
for a similar purpose and proposing digital TV transmission to make HDTV
obsolete, it seems, even before it's gotten started because HDTV;s start's
been postponed a few years.
Nelson Blachman WG6R
Oakland, Calif.
----- Original Message -----
From: "Tom Fowle" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Sunday, April 21, 2002 8:42 PM
Subject: Re: Tech: AM and FM Radio to add digital features
> Message-ID: <[log in to unmask]>
>
> With all the uncertainty about which digital modes might be
> adopted and when, it is still very appropriate for David or some
> such qualified person to be trying to keep the industry thinking
> about accessibility. If it doesn't start now, it will be a
> retrofit, and that is always a worst case choice.
>
> Good luck David
> tom Fowle
>
>
> Net-Tamer V 1.12.0 - Registered
>
>
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>
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