MFJ MFJ-784B, Instruction Manual, Page: 10 / 74

MFJ-784B Instruction Manual
Introduction Error! Main Document Only. -2
Introduction to DSP
The MFJ-784B
tunable DSP Filter

uses state-of-the-art Digital Signal
Processing (DSP) technology. Digital Signal Processing greatly improves signal
clarity by reducing or eliminating noise (QRN) and interference (QRM). DSP
technology has existed for many years but has always been very complicated
and expensive. Recent advances in integrated circuits have greatly increased
the processing power and reduced the size of DSP units. These same
advances also lowered the cost of DSP filtering, making DSP technology
affordable for the average amateur or short wave listener.
The heart of any DSP system is the digital signal processor. Almost any
microprocessor can perform DSP, such as the one in a personal computer,
but only very fast or special-function processors perform DSP in
real time
. A
digital signal processor's commands are tailored to the type of instructions
used in signal processing. The use of special DSP commands allows a DSP
filter function to be completed in very few clock cycles (usually one). The CPU
in a typical personal computer would require a long set of instructions and
therefore many clock cycles to perform the same function. Analog Device's
16-bit 12 MHz processor, the ADSP-2105, is used in the MFJ-784B.
The MFJ-784B DSP Filter converts the analog audio signals from your
receiver to digital information. This conversion is achieved by sampling the
audio signal many thousands of times per second with an analog-to-digital
converter. The result is a string of digital "numbers" that represent the
amplitude and frequency of the analog input signal. The ADSP-2105 chip then
processes the digital information with different digital filter algorithms
depending on the settings of the front panel controls. The end result is a
digitized signal with undesired signal components either reduced or removed
and desired components enhanced. The processed digital signal information
is converted back to an audio signal by a digital-to-analog converter and sent to
the audio amplifier and line level outputs.