In article <email@example.com>,
Curious <firstname.lastname@example.org> wrote:
>What is it?
In the broad sense - any noise which you detect in a signal channel,
under conditions when (in theory) you'd detect no noise at all. In a
purely analog system, this might include hiss from thermal/Johnson
noise, hum or buzz from power supply noise, etc.
Another, more specific use of the term can refer to noise of specific
types which can occur in an analog-to-digital or digital-to-analog
conversion system. Certain types of A/D and D/A conversion system
(e.g. those which use a very high sampling rate, a relatively narrow
converter, and some sort of noise-shaping feedback system) can suffer
from an effect often called "birdies" - a converted signal which
*should* be completely silent, will have a very-low-level audio tone
superimposed on it.
Dave Platt <email@example.com> AE6EO
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