I recently got a copy of the ARRL 2007 Amateur Radio Handbook for reference. I
was skimming the book when I ran into Chapter 16 - DSP and Software Radio
Design - written by Doug Smith (KF6DX). Doug was a key contributor to the Orion
V1 DSP code (Not the V2 code - which is very different). The Chapter does an
excellent job of explaining the functionality and design approach used in
developing the Orion V1 code - although the discussion is intended to be
"generic." Although all of the chapter is very interesting, V1 firmware users
will get a good look at the "Noise Reduction" approach in the discussion of
Fig. 16.28 - An Adaptive Predictor. Page 16.28 gives a very good description of
the two level AGC code and the very elegant AGC offset code used to eliminate
AGC pumping from signals that are inside the roofing filter but outside of the
DSP filter bandwidth. Page 16.16 gives a good description of the Speech
Processing code, which yields some excellent speech processing perform
ance. All in all, this chapter gives a very insightful view of the design and
functionality of the V1 code.
Doug does an excellent job of walking through the various aspects of the DSP
based radio. He also did a nice job - all be it unfinished (But outstanding in
performance) - of developing much of the V1 DSP code.
73, Merle - W0EWM
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