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