Does anyone have experience and/or recommendations
for analogue and digital I/O interfaces based on the Universal
Serial Bus (USB)?

Just an idea for the genesis of a homebrew spectrum analyser.



I can't give any specific advice about the USB interface, but I recall that
there was a PC based spectrum analyser published in QEX within the last
couple of years.

If you don't already, I would recommend subscribing to QEX, it's published
quarterly by the ARRL. It contains a lot of leading edge technology. A
Google search will give you more details.