To Whom It may Interest:
I am working on a high altitude balloon tracking project using the firmware of this project. The mock-up of the circuitry includes the Arduino/SI5351 with a uBlox GPS receiver.
To test the mock-up the SI5351 antenna output feeds to an RTL-SDR.com USB TV receiver at 20m/14MHz. GQRX is my SDR receiver software, feeding WSJTX. I believe my computer time is correct.
When I connect the RTL-SDR to a rooftop antenna, I receive and decode WSPR from several locations, including Europe; I am near NYC. However, when I connect the RTL-SDR directly to my SI5351, I seem to receive the signal all the way through to WSJTX, but it doesn't get decoded.
I'm not sure where to go from here, what to change, or what to test. Any help is appreciated. Some screenshots to settings and current results are attached.
FWIW, Some of the things I have tried:
- calibrating WSJTX to RTL-SDR: slope and intercept
- GQRX Input Hardware AGC and LNA adjustments (off and 0 for direct to SI5351)
- GQRX Audio Gain adjustments (-50dB, 0dB, 50dB)
- GQRX Receiver AGC adjustments (fast and off)
Thx,
Jeff
