DART-70
=======

In 2023, the 70MHz band became accessible to amateurs in Switzerland. This offers an excuse to build a transciever.

The hardware design is licenced under the "CERN Open Hardware Licence Version 2 - Permissive", see *cern_ohl_p_v2.txt*.
The firmware is MIT-licenced.

See dart70-blockdiagram.pdf

Fits in enclosure Hammond 511-0900

New *ongoing*: PA with AFT05MS031 in kicad-dart-70-pa/

## To order

Things that are not on the schematics:

  * Microphone MH34-B4B
  * Adafruit 292 and 181
  * Cable 15134-0800
  * encoder and potentiometer knob (6mm shaft diameter) 5164-1101
  * right-angled 2.54mm headers HMTSW-108-08-T-S-180-RA
  * Enclosure 511-0900
  * Hardware: 20x 970050354

## Board bringup
1. LDOs and VRX VTX switching
2. STM32F103
3. Si5153
  * Frequencies
4. Sort crystals for filter
5. Antenna switch
6. RX path
7. TX path

## TODO

* Firmware:
  * Handle VOX PTT
  * Implement CW macros

## Rev. 0 Insights

* TX Frontend:
  * The amplifier is actually frequency selective enough that we can entirely
    drop the input filter.
  * Instead, we want a trim cap for C120, slightly smaller than 22pF


## Notes
* Mixer termination
  * https://www.qsl.net/g3oou/mixerterminations.html
  * https://www.changpuak.ch/electronics/calc_16a.php
  * http://land-boards.com/blwiki/index.php?title=Kits_and_Parts_Mixers

SPK click:
LM386 was wired as 46dB gain on Picardy 2020

LM4865 (20dB gain) + gain stage
and volume control like
https://www.mikrocontroller.net/attachment/315502/Zwischenablage01.png
https://mbonnin.net/posts/2011-01-05_bwaaaaaaaaaaaaaaalarm-clock/lm386.png

https://groups.io/g/BITX20/topic/4995877