Shipping hardware internationally is a hard, labor intensive, and overall a frustrating process - especially more so these days.
Here is our plan to supply the DDX to customers:
Make the hardware files free / low-cost. The users will be able to order fully assembled boards from JLCPCB or other vendors on their own.
Required a small licensing fee for the software firmware part. This is how we get to keep the hobby self-sustaining!
Future DDX architecture ideas (from Ismo and other folks):
Antenna ➔ CD2003 ➔ 455 kHz IF ➔ Ceramic filter SMD (HCI) ➔ "IF amplifier" needed? ➔ Pico 2's ADC ➔ Down-conversion and processing in digital domain ➔ Expose the processed audio samples over USB (Pico 2 acts as a sound card).
Benefits: This enables reception of SSB and CW signals!
Alternate easier and traditional radio architecture:
Antenna ➔ CD2003 ➔ 455 kHz IF ➔ Ceramic filter SMD (HCI) ➔ BFO mixer ("product detector") ➔ Direct Sound output ➔ Pico 2's ADC ➔ Pico exposes the audio samples over USB
Alternate ideas: One of the more promising and well-tested CD2003 designs is documented @ http://www.kh-gps.de/cd2003_rx.htm. This actually looks like the most promising option!
Immediate architecture (for DDX-Commercial series):
Antenna ➔ RX path ➔ SMD BPF (7 to 28) ➔ CD2003 with AGC ON ➔ Small "emergency" 10k SMD pot to tweak volume one time ➔ (X)MCP6022 (fixed gain, MFB with LPF action) ➔ RP2350 2's ADC
In other news, I got a DX 100 award with DDX on 10m recently - w00t!
References:
https://github.com/steve-m/hsdaoh-rp2350 (see
internal_adcsection)This way we can continue using
RP2350instead of moving to something likeSTM32H5immediatelyBFO handling code: https://github.com/mpmarks/pico-adx/blob/master/src/main.cpp