Hi John,
The BB60A is capable of being tuned down to 9kHz in the HDSDR application. If you have access to one, great. The SA44B is a good choice for low frequency audio decoding as well, and more affordable as well. If your only goal is low frequency audio, you might look into dedicated SDR hardware, but obviously, this is not possible if you still need a spectrum analyzer.
I would be more than happy to answer any questions you have on the SA44B.
Regards,
A.J.
