In article
,
Booble wrote:

On May 27, 6:49?pm, "Bob" wrote:
Are you refering to the DRM signal interfering with adjacent analog
transmissions or the other way around?

"Booble" wrote in message

...



My understanding is that DRM on Shortwave acts just like IBOC on AM,
with adjacent-channel interference. Is this true, and has anyone
noticed sideband interference coming out of 9800 Sackville? I picked
up Radio Canada International ?today, and did not notice interference
from them...- Hide quoted text -

- Show quoted text -

Yea, doesn't DRM also have digital saddlebags as IBOC?

Digital mode transmission spreads out due to square waves being
composed of odd harmonics. You need at least the first two for a square
wave to have its basic shape and so 1, 3, and the 5th harmonic. For a
square wave that looks very much like you would expect you need
1,3,5,7, and the 9th harmonic, 5 total, so you can maybe get the feel
of how a digital modulated signal needs to spread out occupying a wide
swath of frequencies.

The current scheme to minimize this spread of modulation harmonics IBOC
or DRM is to use multiple carriers switched on and off at an audio
rate. The problem here is that these modulation algorithms are not as
efficient as analog modulation regarding frequency efficiency. This is
one of the dirty secrets of current digital modulation schemes. There
are upsides to using digital mode but you will use up more the
frequency spectrum to get it.

This multiple carrier idea is old technology for either IBOC or DRM.
The only thing remotely new are the algorithms used to digitally encode
the audio before that is applied to the modulation algorithm.

This mix of audio digital encoding and modulation scheme has a tendency
to appear as a random square wave modulation of the carrier, which
completely fills the occupying spectrum used. This creates the
"saddlebags" you mention.

Digital mode is fundamentally incompatible with analog channel
assignments and as such is part and parcel of the folly of mixing
analog and digital modulation modes in the same band. In other words it
is just plain stupid decision making.

Old technology coupled with dumb decisions equals the mess we have to
deal with on a daily basis now on AMBCB and the SW bands.

--
Telamon
Ventura, California