[Elecraft] P3 Photo

[David Woolley (E.L)]

Steve Ellington wrote:

> photo it appears that the display is not averaging the signals as Flex 
> SDR. The QRN appears as little signals. With the Flex SDR- LP Pan, QRN 
> moves the entire base line up and down slowly but doesn't seem to appear 
> as a mess of little peaks, masking the actual CW signal. That's the 
> amazing thing about the I/Q system. I wonder if the P3 has the same 

Averaging across multiple FFTs isn't related to whether or not I and Q 
feeds are used.  Using I/Q feeds is just a way of running the A/D 
convertors at half the speed for the same overall bandwidth (although at 
the cost of having two A/D convertors, two mixers and more complex local 
oscillator circuitry).  I think it also reduces the DSP power required 
by about a factor of two, as one solves for both positive and negative 
frequencies, whereas the negative frequencies from a single mixer are 
the same as the positive ones and are just thrown away at the end of the 
processing.


-- 
David Woolley
"we do not overly restrict the subject matter on the list, and we
encourage postings on a wide range of amateur radio related topics"
List Guidelines <http://www.elecraft.com/elecraft_list_guidelines.htm>