DART-70
=======

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

* Separate things a bit more than on Picardy 2020
  * One HF SSB/CW exciter PCB with:
    * Voltage regulators
    * Mic input from Picardy 2020
    * AGC measurement like Picardy 2020
    * AGC IF amp better than Picardy 2020
      * VEXIBITX applies AGC at HF input instead, and uses uBitx amplifiers for IF
      * uBitx has no AGC
      * Hybrid Cascode? (Implies IF between 8 and 12 MHz)
    * Frequency plan:
      * What HF intermediate frequency?
        * High-side mixing? need low-pass to reject image, also rejects FMBC
          * 96MHz oscillator: 26MHz IF
        * Low-side mixing (kuhne and anglian do that)
          * 42MHz oscillator: 28MHz IF
          * Prefer, can't be wrong if others do that
        * Reuse Anglian 3L oscillator from lo_board/lo_board.pro
      * VFOs Si5351A-B-GT for first two mixers
    * Mixers (3 needed: VHF, HF, AF)
      * AF: like VEXIBITX
      * HF: like uBitx (BAT68-04W ring mixer, see doc/ubitxv6.{txt,pdf})
      * VHF: MCL RMS-11X (+7dBm LO) or the macom one? (missing from inventory)
    * XTAL filter QER like uBITX at 11.0592 MHz
  * One PCB with HF-4m transverter, inspired by Anglian
  * One PCB with 4m driver, PA and antenna switching
    * We are allowed 25W ERP, aim for 10W PEP
    * BCW71 driver, 2SCR573D3 push-pull amp?
    * How about STN4NF20L?
    * LNA: SPF5189Z
  * One PCB for frontend
    * Connected by cable to the main board
    * Microcontroller, Display, Encoder
* Enclosure: Hammond 1411R or 513-0900?

## To order

* Adafruit 292 and an i2c display