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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
* 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
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