[Premium-Rx] R&S PR100 IQ demodulation mode?

[Matt Blaze]

Hi all,

Apologies for not being very active here lately, but perhaps someone knows the answer to this surely terribly dumb question.

I recent got a Rohde & Schwarz PR100 portable receiver (this is their current model, replacing the EB200).  One of the features that I really like is its ability to store on an SD card (or stream over the network) baseband IQ data, for up to a 500KHz band.  (This effectively allows you to store a little chunk of spectrum for later analysis.)  This is independent of the demodulation mode -- the same data is stored (or streamed) whether you're demodulation the audio as FM, AM, CW, whatever.  (Demodulation happens after the IQ data is calculated).

OK, I understand the principles of IQ data, and I've managed to parse the R&S IQ data format, so all is good there.  But the receiver ALSO has an "IQ" demodulation mode.  And I can't for the life of me figure out what it's for, what it does, or what the audio actually is.  It seems to inject a BFO, but it's neither FM nor AM.

Any idea what this mode is?  The manual is of sadly little help.

I vaguely recall the EB200 also had IQ demodulation, and I didn't understand what that did, either.

Thanks for any advice!

-matt