Telamon wrote:
In article , craigm
wrote:


Tom Wells wrote:

Thank you for explaining the mysteries of modulation byproducts and
bandwidth in a way that makes the truth clear for people who may not
have had radio schooling. Instead of making it sound harder than it
really is..

The saddest part of it all is that MOST of the digihash flamethrower
noise is describing to the demodulator that no modulation is present
for most audio frequencies.
Even if NO audio is present, the IBOC signal is still 45khz wide,

The bandwidth used by IBOC is 30 kHz, not 45.



describing each and every one of the possible audio passband
frequencies as 0% modulation. Instead of just letting there BE no
modulation, they've decided it's much better to have all these little
subcarriers elaborately screaming "NO MODULATION AT 1200HZ!" "NO
MODULATION AT 1201 HZ!", etc. It's like having a thousand people in a

There is not a carrier for each discrete frequency.


room screaming about nothing. In proper engineering, like with good
manners, if you have nothing to say, you keep your mouth shut.


You need to better understand the modulation method and how digital
decoders work.


Telamon wrote:

snip

This is a simple concept that many people don't seem to get.
Information rate directly correlates to bandwidth in this way, higher
rate and more detail means larger bandwidth. Analog or digital is just
a method of encoding information. Narrow filtered analog is similar to
low rate digital. It does not matter what digital method you use you
can't get around the fact that a better picture or audio means you need
to use more bandwidth.

Oh, but it does matter. The choice if digital modulation and compression
change things.

For a given modulation method and compression scheme, what you say is
valid. More content means more mandwidth.

However, different modulation methods and compressions schemes result in
differing bandwidth requirements for the same amount of content.

If this isn't true, then PC modems would still be running at 1200 baud.


One reason newer PC modems have higher baud rate it that they use more
bandwidth than the old ones did.


PC modems are limited by the bandwidth of the phone line.



I'm sorry but there is a direct correlation between bandwidth and
information that can not be changed. Compression methods are not some
kind of black magic that can stuff more information in the same number
of bits. Compression methods can cause a digitized description of analog
information to be more efficient and some methods are better than others
but that is it. An example would be a picture of a checker board could
be described with fewer bits because there is not that much information
but change that to a wide view of scenery where every bit is more random
and it can't be compressed to any extent. Compression can not cause a
better "digital description" using the same bandwidth to occur as analog
representation of the same.

To be abundantly clear here my point is that DRM can not sound better
than analog in the same bandwidth.


There is more then one way to encode the analog world into digital and
back and some methods are more efficient then others but there is no
magic digital encoding system comprised of one or a combination of
encoding methods that will magically stuff more information into the
same bandwidth.

The DRM controversy has gone on for a long time where the claim that
DRM sounds better then analog in the same bandwidth. This is a bunch of
BS. Not only does this violate the laws of physics it further makes
less sense from the standpoint of conversion of analog to digital at
the transmit end and then digital back to analog at the receive end.
Technically changing from analog to digital and back introduces
conversion errors so DRM in the same bandwidth has to sound worse than
analog. The only way DRM can sound better is to use more bandwidth than
analog.

You are completely ingoring compression and modulation methods.


Yeah, it is not germane to what I wrote.


Yes, converting analog to digital then back to analog will degrade the
analog signal. A straight wire is always better. However AM, radio is
not a straight wire.


This is all a given.


With AM radio, an analog signal is compressed, band width limited,
converted to electromagnetic waves, mixed with any other waves on the
same frequency between transmitter and receiver, converted to an
electrical signal, passed through an IF that further bandwidth limits
the signal, and then run through a detector that usually adds at
least 1% distortion.


Now you are bring other issues into the picture. I want to ignore these
issues also.


So there are are two basic concepts for anyone reading the news group.
DRM and IBOC claims are a bunch of BS. Analog or any digital system
will sound better the more bandwidth you use.

I can compress audio to a 64 kbps data rate for an iPod. This sounds
better than _any_ AM broadcast I have ever heard. Better signal to
noise, lower distortion, better audio bandwidth and stereo.

I've also heard FM band IBOC, and I will say that it did sound better
than the analog channel. However this may have been due to significant
amounts of signal processing at one end of the chain or the other.


Music from an Ipod is not short wave analog or DRM.

The point of my post is to dispel the notion that DRM can sound better
in the same bandwidth space as an analog signal and the basic theory
behind the reasoning, it can not regardless of the compression
algorithms and modulation scheme.


The encoding method for iPod and DRM and both forms of AAC.

My point is that it is possible for DRM to be an improvement.


(And no, I have no desire for IBOC on the AM broadcast band. I think
there are too many associated issues, the primary one being the
consumption of 30 kHz bandwidth. IBOC on FM may work and be viable in
the long run.


I'm not either. At the least they should split the existing band between
IBOC and better would be another band.


I am in favor of DRM.)


I'm not.