Hi Mike,
Although I have no experience with the sBITX, I agree with the advice from Mark and Evan.
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Both Mark and Evan were very helpful to me, when I ran into difficulties in the process of upgrading my uBitxV6 to a Nextion display with KD8CEC software, including the "standalone signal analyzer i2c type" which utilizes a second Arduino Nano. Most of my posts on this forum were related to these issues. If you search for my posts, you should get a good idea of potential modification hazards. Of course, I would be happy to discuss my experience directly (although I would need to reread my posts, to refresh my memory).
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The worst of the problems required replacement of the si5351 chip, which generates the three clock frequencies essential to the radio's operation. (Apparently, it was damaged by static discharge in the modification process.) Secondary problems were mostly related to difficulties with frequency and BFO alignment. In retrospect, I almost gave up on the project. But the end result was an improvement over the factory radio.
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Now that the radio is working, I am quite happy with it. There really is no need for additional CPU power... except to improve non-essentials, such as spectrum display and CW decode functions. Both of those are included in the KD8CEC software. Mark's software releases have improved those and other functions, as compared to the KD8CEC original. But neither of those features works very well, in my opinion.
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I was very interested in Mark's work with more advanced CPUs. He sent me a prototype board with the latest version of his KD8CEC software preloaded on an RPi-Pico. It works well. But I can't see any real improvement over the Arduino-Nano versions... the non-essential features were not well supported on the prototype. No doubt, he would have improved those features, too. But since he doesn't see a future in that direction, that's as far as I will go (since I'm not as technically astute as Mark or Evan).
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My typical usage is SSB and js8 (interconnected with a laptop computer). I also added a simple AGC circuit and an audio bandpass filter for CW work. However, I have not actually used the radio for CW. If you are an avid CW operator, you might explore alternate software, such as the K8NE VU3GAO firmware (which does not require more CPU power).
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DaveW, KL7HJF
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