Russ, thus far, pretty good. So I have a TS-570DG and TS-890S that I am trying it with. (yes, I know, both have MPUs for doing signal processing and NR).
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I find the NR, NB and Morse decode functions in the TS-890S to be very good. My ultimate desire though is to use this circuit with a Realistic DX-302 SW receiver (remember those of the 1970s?). I purchased one last year, which has none of the processing capabilities of the 570 and 890. That was one motivator for building Graham's project.
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Also, my desire was simply to get exposed to the practical application of this area of study.. Over 35yrs ago, I was pursuing a post-grad degree at GA Tech, and at the time, taking classes from professors well known and published in the field of Digital Signal Processing. Unfortunately, most of the concepts and theory I learned then exists amongst mental cobwebs at this point. It's often said, what you don't use, you lose.?
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Tom - this is DSP in the aft-end of the audio chain. Graham's project does not perform signal processing in the IF-stage, but I think you'll find this a worthwhile project.
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It's not too dissimilar to the DSP modules made by BHI (the NEDSP boards). Years ago, I put one of those into a TS-440SAT with pretty dramatic results. I have a write up for it on the Kenwood TS-440S Groups.Io forum in the Files section and another person posted a YouTube video on it.
Interestingly, while the results were very good with the BHI module, there were many artifacts (like sounding under-water) in that implementation when going to the highest setting of NR, that I do not hear with the Teensy. The Teensy implementation is also much less expensive!?
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FWIW: In the files section of the TS-570 Group.Io, I placed a write-up for installing an IF tap for SDR Waterfall Display in my TS-570DG. I like to experiment, and Kenwood makes great products. So blending new and older technology is a great aspect of our hobby.
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I'm assembling a few photos now and will post them here in the file section tomorrow (Saturday) which covers initial prototyping of the circuit and specifics to assembly which may be of help others. I think I'll post my notes as well. Then I'll go the next step to revise those notes, and provide information regarding the software and installing the necessary elements on a PC.
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Graham's README.md file covers a lot that should be read first, but I did need his help so I think I can distill some of it to help people get over the "activation energy" needed to purchase the parts and give it a go if interested.
73 W7STF S.
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