Page 5
Overview
Continued
The noise reduction functions of the DSP-8200d operate by examining a characteristic of
signals and noise called
correlation
, and dynamically filter out the undesired signals and
noise. The degree of correlation is relative. Random noise such as white noise or static is
uncorrelated. Speech is moderately correlated. Repetitive or continuous noise such as a
pure tone is highly correlated. The DSP-8200d combines these three basic functions to
reduce noise and interference and improve radio communication.
The DSP-8200d measures correlation and filters out signals and noise that are outside its
correlation thresholds. The amount of noise reduction varies according to the correlation
characteristics of the noise. Typical noise reduction ranges from 5 dB to 20 dB for
random noise and up to 50 dB for tones.
A squelch feature is also implemented in each mode. The DSP-8200d squelches silent
channels (no communication in progress) so that channel noise is very low. This feature
is particularly important when multiple channels are being monitored by the same
controller.
Should the need ever arise, each DSP module is field reprogrammable using an ordinary
notebook computer with an RS-232 serial interface.
System Description
The DSP-8200d consists of a 5-1/4 x 19 inch rack mounted card cage chassis, 12 plug-in
DSP modules, a Control module, and two redundant Power Supply modules.
Card Cage
The card cage chassis is built around Euro rack standards. Access to modules and cabling
is from the rear side of the chassis. Status LEDs are on the chassis front panel and
duplicated on each module.
