Grant (NQ5T) said:
"NR works in a variety of ways, including using LMS or some other adaption
algorithm to adapt the coefficients of an IIR or FIR filter, in the classic
Wiener filter noise reduction algorithm."
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Grant,
I believe your comment is correct and my earlier comment was in error. The
other documentation I have seen on V1, and early V2, DSP firmware simply
described the NR system as an "adaptive filter system" and did not specifically
indicate it was "predictive" (The earlier reference is still very helpful in
understanding the concepts used in the Orion V1 noise reduction
-----> http://www.doug-smith.net/kf6dx3.pdf <------- ). So I will stick with
the story that in V1 and early releases of V2 the NR algorithm is an "adaptive
filter driven by an LMS algorithm with some forward leakage." And, I like the
way it works in V1 :-) I have no idea what is in the current release of V2, but
I also would join in asking TenTec to provide a "Theory of Operation" document
for the current Orion V2 code. I agree that Doug's articles describing both
the Orion http://www.doug-smith.net/orion.htm
and special areas like the "interaction of the analog and digital AGC
http://www.doug-smith.net/digitalagc.htm " helped in understanding the Orion V1
"Theory of Operation."
Although the V2 code has significantly redesigned the Orion radio (As pointed
out in the ARRL review of the Orion II), and changed its performance, I agree
that we are all "in the dark" with respect to the current V2 DSP firmware
design. It seems the hardware guys are willing to document their designs (Lots
of schematics) but the software folks are not willing (Or able?) to even
provide a current theory of operation or operating block diagram for the V2
firmware. Although I certainly can not "change the DSP code," I find that kind
of documentation an important aid in trying to better understand operating
problems/bugs and that it helps to "frame some diagnostic testing."
73, Merle - W0EWM
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