What about taking this 500kHz signal and use it as LO for another SDR setup. Well, that would provide as with a centre frequency of 125kHz.
Assuming a regular 48kH sampling, two interesting frequencies are in reach:
- MF: 476-524kHz
- LF: 101-149kHz
|The loops for 30m and 40m.|
|The gap in the shield, opposite the capacitor.|
|The capacitor and coupling "box".|