Re: Are the uBITX receivers ripe for improvement? -- And some other miscellaneous thoughts.

iz oos

Sensitivity is fine. I have used an homemade norcal S3 generator to see if it could receive it and was right. I check all receivers with it and all from ham radio, mil rigs and cheap portables behave like that. All have plenty of sensitivity just like dongles. I would add an accessory like the inrad output for the IC-7300 to add eventually an external preselector. And I would add to buffered outputs before and after the filter to add an sdr receiver. In any case it would not become an elecraft K3S as the oscillator has more phase noise so close very strong signals will increase the overall noise level of the receiver and in that case you can only use an attenuator. The 8bits cheap dongles have an extremely limited dynamic range and I would never use them unless in the outputs of the Ubitx I described before where all the filtering is done before. I have to say the receiver is well designed and adding an sdr in the chain can really add everything can desire, given the limitations of the phase noise.

Il 13/mag/2018 05:10, "Tom, wb6b" <wb6b@...> ha scritto:

I see a lot of good conversations here about improving the uBITX transmitter output. However, I see very little about how good the receiver is. My question is, have many people done comparisons of the uBITX receiver vs their other radios; particularly on SSB?


In my case I have noticed that my SDR using a cheap dongle seems to outperform the uBITX receiver substantially. Even though I don’t consider the SDR dongles to be the pinnacle of RF design, I guess throwing brute force real time math at the receiver side makes up for some of it.


Are the uBITX receivers ripe for improvement?


Additional miscellaneous thoughts:


Rather than cutting up the uBITX or trying to cram more software into the one Arduino Nano on the uBITX I was pondering running multiple Nano’s communing on the I2C bus. They are only about $3.50 apiece. (The 3.3v bus [albeit barely] is in spec for the Nano.) 


But, rather than cutting up the radio I think I’d rather simply treat the uBITX as a peripheral to a Raspberry Pi. I’d place the Pi (and USB audio adaptors) in a metal box packaged in the same case as the uBITX.


What I’d do with the Pi is:


  1. Process and level the microphone audio for transmitting.
  2. Process, level and noise filter the receive audio, as well use a DSP library to add bandpass and notch filters.
  3. Use one of the digital mode libraries for digital mode communication. 
  4. Maybe get rid of the T/R audio pop while processing the receive audio. 
  5. Control other gizmos I may add to the transceiver.
  6. Put a fancy touch screen display on the whole thing.

Additionally, I’m doing a literature search to see what work has been done on training Neural Nets to decode Morse Code. It would seem that a technology that can identify people, dogs and cats from low resolution photos (although there was a study that found AI could mistake pictures of muffins for chihuahuas), could finally realize an adaptable, reliable CW decoder. (This would run on the Pi, also).


I’m sure others must be working on the same things. Anyone know about such projects. That would save time over starting from scratch.

Tom, wb6b


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