Picardy 2020
============

A reinterpretation of the [Picardy 2m SSB transceiver](http://f6feo.homebuilder.free.fr/transceiver_PICARDY.html) by F6FEO
combined with the [Anglian 3L transverter](http://www.g4ddk.com/Products.html).
Additional inspirations: uBitx, the KN-Q7, LimeRFE and EI9GQ's "Building a Transceiver" book. Many thanks to all the
designers behind these projects.

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.

* Designed in KiCad
* Meant to be used with a microwave transverter
  * But also stand-alone 144MHz
  * Offer plug-in band-filters for other HF bands
* Using a STM32F103C8T6 controller
  * Programmed in [Rust](https://rust-lang.org/)
  * Si5351 clock source (generates  clocks)
  * An LCD display
* Discarded ideas
  * Include a Lars Widenius GPSDO originally published on [eevblog](https://www.eevblog.com/forum/projects/lars-diy-gpsdo-with-arduino-and-1ns-resolution-tic/?all)
  * Offer a 10MHz output refclk for a transverter
  * Instead, have a 25MHz ref input, and use a LeoBodnar reference
  * Use the Si5351 to generate the VHF LO at 116 MHz
  * It wasn't clean enough, so a separate [XTAL LO board](./lo_board/) was designed
    * With a 114.286 MHz crystal, we get a first IF of 29714 kHz

*First QSO done with this transceiver and MMRF1021 amplifier on 2020-12-07*

On RX, an [LNA4ALL](http://lna4all.blogspot.com/) LNA was used. On TX, 2x SPF5189Z, a bandpass filter to remove the LO,
and the [MMRF1021](http://git.mpb.li/git/mmrf1021-pa/about/) amplifier were used, giving about 200mW output power on the
very first trial.

Open questions
==============

* CW
  * Does the trick with the DC bias to leak the LO work ?
    * Not tested, but plan B done (J306)
    * Use an additional PWM output for plan B?
  * Put sidetone volume setting before RV303?
    * Hook up to LM375 BYPASS?

Issues
======

* Coupling between VHF filter coils was way too large
  * Fixed, replacement of coupling caps.
* SEQ0 is used in inverted-logic in baseband, and noninverted for power relay
  * Due to inconsistent naming
  * Ugly fix on K603 side, use SEQ0n, SEQ1, SEQ2
* G6K-2F-RF all have the Y footprint, not the equidistant one.
  * And they have additional GND flaps too, which are not in the Kicad footprint library
  * Can be kludged-in
* 5V jumper is less useful as hoped
  * Intention: disable VHF stuff
  * Unintended effect: removes LCD backlight
* C319 and C326 are redundant
* BC856W wrong footprint
* R327 upsets DC offset of audio amp, capacitive decoupling needed
* 2m LPF from LimeRFE use values I don't stash
  * 20pF done with 2x 10pF
* SW: ADC input for buttons looks messed up...
* Connect 3V3 LDO to 12V directly
* Add 2.2uF caps near consumers
  * Replace C535, C536
  * Replace C343, C315
  * Next to R508
  * Next to R305
  * Parallel to C331
  * Parallel to C607
  * Next to R306
  * Next to R504
  * Next to R328
  * Next to R515
  * I still have spurious next to transmit frequency, spaced 200kHz because of the DCDC converter
  * Measure 8V current!
* Added 100nF caps on microphone connector to suppress RF being coupled

PCB Assembly Plan
=================

1. DCDC converter for 8V and LDOs
   * Check output voltages
   * Check drop under load

2. STM32F103C8T6
   * Programming
   * Sidetone low-pass
   * Probably need to do a UI proto already

3. Si5153
   * Check I2C works

4. 8V and 5V relay
   * Check switching with microcontroller and validate resistors

5. Baseband
   * Crystal filter shape
   * RX and TX filter shape
   * Receive path: IF mixer, crystal filter relay, IF AGC, BFO mixer, AGC measure, AF amp, SPKR
      * Verify LO levels into SA602A: at least 200mVpp
   * Transmit path: Mic amp

6. Anglian
   *  LO filter shape
   *  LO amp. Mixer needs +7dBm
   *  All passives
      * Verify correct voltages for amplifiers
      * Verify PIN currents (Between 20mA and 60mA, below 0.8V)
      * Verify filter shapes
   *  IF amplifiers, both RX and TX
   *  VHF amplifiers
   *  VHF bandpass filter
   *  Mixer

7. External switching relay


Tuning
======

IF gain (R307)

Define if we need C361, C360

Ensure LO1 and BFO voltage level at TP301 TP302



Additional remarks
==================

Very good [explanations](https://groups.io/g/BITX20/topic/si5351a_facts_and_myths/5430607) about DDS vs DPLL from Hans Summers

Si5153 test before PCB fab:

* It seems the desired frequency plan can be achieved:
  * clk0: LO1 = 28 - 4.9152 + VFO, i.e. from 23 to 25
  * clk1: VHF-LO = 144 + 28 and 144 - 28, i.e. 116 MHz
  * clk2: BFO = 4.91521
  * See `freqplan.py`
* If not, generate LO1 and BFO with Si5153, and connect an external LO to the VHF LO u.FL
  * No 116MHz crystals on mouser, but 114.285MHz are available, HF bandpass filters recalculated.
  * Other option is using another configurable reference