https://www.eevblog.com/forum/microcontrollers/getting-dsp-basics/msg1924066/#msg1924066

I'm hoping the thread is dead and stays that way. I got sucked into when GeoffreyF said you *had* to use quadrature  to do DSP.   I think the source of the conflict was a BS EE view of DSP vs a PhD geophysics view which is rather broader than what someone learns at the undergraduate level in EE.  If you read the thread, you'll see that he did not get my point that you need to be able analyze a DSP problem with pencil and paper from knowledge of the common transform pairs to really be good at DSP. One of the great pleasures of my career was a period of several years when I had a *very* sharp Stanford grad across the hall.  We often walked in each other's office and started graphically analyzing various DSP problems on the white board as a preliminary step before implementing the idea.  Usually one of us would recognize some detail the other missed, so it was a great time saver. "No, that won't work because....".

When most of the people along the hall have PhDs from the absolute top schools you do *not* make comments such as this:

I'm extremely annoyed that I can't find the other PDF because the opposite image rejection is incredible.  I *really* need to reorganize my file system.  It's this God awful assortment of stuff spanning many years and many computers.  I've started on the chore a number of times, but eventually get so confused by several TB of duplicates  made worse by the fact that I'm actually running several computers plus a couple of VMs.

edit:  found the hard copy :-) cbjohn.com/aa0zz/PPLLUsers/W6JL/W6JL.pdf  My memeory was incorrect, it's only 60 dB of opposite side band suppression.  Still very impressive performance.

I've got one MSEE thesis and a PhD dissertation IIRC on the topic of mixers which provide a detailed analysis of quadrature mixers.  The PhD dissertation includes a detailed comparison of the performance of a number of mixers.

I'd guess that the reason the NorCal2030 doesn't appear in the list is lack of a unit to test.  They only assembled 100 kits and it's a rather complex radio.

I found out that some versions of the STM32F4 have ADCs which are plagued by on chip noise.

I can think of two likely problem areas for quadrature mixer builds, the output level and timing of the two ports and the linearity of the ADCs.

The problem with the big slurp is the data rate.  There is a really nice 16 bit SDR build in a recent QEX.  It's an eval board for a 125 or 150 MSa/S from AD and a ZedBoard plus packaging and software.  But that's a $1200 build.

I'm not interested in contesting nor in collecting wall paper, but an RPi + STM32F4 Discovery board HD display of 3.6 MHz of the HF band allocations seems to me would be a very attractive shack decoration for a contest or DX enthusiast.

Alberto, I2PHD has a nice STM32F429 based SDR:

http://www.sdradio.eu/weaksignals/armradio/

My personal interest is more in investigating propagation phenomena.