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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
* Measure driver output
* Measure antenna switch insertion loss
* Fix AGC
* 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
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