ARROW uBITX Group Purchase

Things related to the uBITX radio group purchase made by a number of ARROW members.

Mailing list for all BITX radios: https://groups.io/g/BITX20

Huge resource page by ZL1AXG: http://ubitx.net/

Map of BITx users: http://bitxmap.com

Problems, Issues and Glitches - significant issues reported by builders

TDA2822 stereo amplifier high failure rate
- Reported on the mailing list, Some ideas discussed there:
  - Replace with 8-pin socket and NJM2073D
  - LM386 + adaptor
- <link(s) to best discussion(s), fix(es), etc(es)>
Power output differences across bands
- http://ubitx.net/fix-fix-uneven-tx-output-across-bands/

Building Hints and Tips

Operating Hints, Tips and Warnings

DO NOT insert a mono plug into the stereo audio jack -- this shorts the output of the audio amp and will likely blow it up

Recommended Mods

Advanced Mods

AGC circuit
- K9HZ summary of options
  - ... audio range passband...Benefit: saves your ears, $0.02 diode, trivially easy to implement.Bad: only protects your ears... not RF sections from excessive signal and overload. Not a true AGC signal for "s" meter, only an audio strength.Comment: Save the $0.02 diode, turn the damn volume down and live with the IF overload.
  - ... IF range passband...Benefit: Saves ears, prevents IF overload, AGC signal for "s" meter (can be calibrated to real signal strength by reference).Bad: More complicated/ more parts, RF level attenuator and AGC response, more expensive than the $0.02 diode,Comment: can be triggered by anything in the passband and that can be good and bad.
  - ... Full range integrated Passband (front end through audio section)...Benefit: True AGC on all levels, no overload or distortion of any stage. AGC signal for "s" meter (can be calibrated to real signal strength by reference).Bad: Very complicated, impacts every RF/IF/Audio stage. Lots of mods and parts.Comment: A CW ops dream.
KD2NDR port to Teensy

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