[hpsdr] Mercury question

[Mark Amos]

HPSDR'ers

I got the Jan/Ozy combo hooked up and did some CW listening on 40 meters using the SDR-1000 as a front-end to 
supply I/Q.  Sounded good, worked fine.
Really cool!

I took a look at the Wiki and wanted to get a little clearer on next steps.
Particularly on Mercury. 

Mercury will be a high speed direct sampling device (sampling RF.)  This sampled RF will be somehow translated down 
to audio frequency and sent to Ozy, which will then send the digital I/Q over to PowerSDR for demodulation/dsp.  Is 
this right?

How does the "down conversion" / translation from RF to audio frequency occur?  Looks like this happens in the 
FPGA, but what, exactly, does the FPGA do to make that happen?

Also, since there appears to be some audio leaving the card, that there must be some demodulation occurring in the 
FPGA too, is that right?  The text seems to say that a PWM DAC performs this function (integration of the sampled 
RF to do AM demodulation?)

My apology, in advance, if these are silly questions.  (If they are answered in the text, I obviously didn't get 
it...)

Mark


"A long habit of not thinking a thing wrong, gives it a superficial appearance of being right, and raises at first 
a formidable outcry in defence of custom. But tumult soon subsides. Time makes more converts than reason." Thomas 
Paine