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+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 and stand-alone 144MHz
+  * For transverter usage, no PA reduces current consumption.
+  * For stand-alone, see MMRF1021 amplifier below.
+* Using a STM32F103C8T6 controller
+  * Programmed in [Rust](https://rust-lang.org/)
+  * Si5351 clock source (generates HF 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 an external 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.
+
+Later, the external bandpass and 2x SPF5189Z were replaced by an internal bandpass with less insertion loss and a single
+SPF5189Z.
+
+
+*First 3cm QSO done with Picardy 2020 as IF transceiver on 2020-02-21*
+
+Using a Downeast Microwave 10368CK transverter.
+
+
+TODO
+====
+
+* Where does the 1.6kHz offset come from?
+
+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 LM386 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, added 2.2uF capacitive decoupling in series with 1k
+  * PTT makes loud click, assemble with 100nF only, still loud
+  * Connected LM386 back to 8V, through 0 Ohm instead of 10 Ohm (was on 12V through 10 Ohm because DCDC noise). Still
+    loud.
+  * Investigate other muting schemes.
+    * Connecting BYPASS to GND generates click
+    * 2N3819 based muting according to G3YCC works better.
+  * Assemble 1k + 100nF for coupling, revert to 12k for R329, use 20k for R326 to slow down the transition a bit
+* 2m LPF from LimeRFE use values I don't stash
+  * 20pF done with 2x 10pF
+* SW: ADC input for buttons looks messed up...
+  * Four buttons instead of 7 are enough anyway
+* Connect 3V3 LDO to 12V directly
+* Also, replace DCDC by L7808 to improve spectral purity
+  * Actually there would be more to be gained with a DCDC on 5V or 3V3!
+* Added a LM360T LDO for the MMRF1021 so that it can be powered from 3S LiPo (11.1V) and Pb (13.8V) batteries
+* 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
+* Reduce RF coupling
+  * Added 100pF caps on microphone connector and CW input
+  * Added 22pF on DC jack, DIN
+
+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`
+* This ended up being too noisy and was replaced by an external VHF LO, with LO1 and BFO generated with Si5153
+  * No 116MHz crystals on mouser, but 114.285MHz are available, HF bandpass filters recalculated.
+