penfold42
commented
2 months ago Edit: just re-read your final points :)
A better antenna will always help - it will boost the signal to noise ration so the picorx can use a lower AGC. And you could add a single band filter as a quick test.
Mines pretty crappy too but i've used even worse components:
- 74HC4051 and MCP6002 (rather than MCP6022).
- no preamp at all. But I have some high power AM broadcast towers nearby
- It might also have developed a defect. Swapping IQ no longer makes any difference!
Some possible causes of noise:
- Grounding is important - vero/donut/breadboard has no ground plane so its tricky to keep the noise down.
- separate analog/RF and digital VCC and GND connections.
- You might have some LO radiating into the amp if they're nearby.
- Do you have an LC band filter? My hack job has some provision for dropping these in.
- OLED charge pump noise. The TruSDX guys were modifying the oled so they could disable it IIRC
I've finally received the last components and build Tayloe detector. Assembled everything partisan style on a veroboard. It definitely works. Here is a sample recording: pico_rx_1.mp3.zip
There seems to be however a lot of noise everywhere. What can I do to improve this? Bandpass filters? Better antenna? Maybe some wires need to be shielded (LO_Q, LO_I?)?