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

* Enclosure: Hammond 511-0900

Receive gain:

S9 is -93dBm, S1 is -141dBm

-141 -1 +16 -1 -7 +16 -4 +60 -7 +30 = -39 dBm


Transmit gain:

-6 -7 -4 +16 -4 -7 -1 -1 +15 +15 +15 -1 = 30 dBm

## To order

* Microphone MH34-B4B

* Ordered:
  * 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:
  * Adapt clk settings for 11MHz IF
  * Handle VOX PTT
  * Implement CW macros
* Add silkscreen info for headers, pinouts and testpoints
* Clearance for ethernet magnetics
* Placement and clearance for front connectors


## 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