Re: explaining i/q

David,



On 4/11/2020 01:18, David Hagood wrote:
> I am sorrowful that you have decided you are going to stick with an
> explanation that is fundamentally incorrect. I know how direct
> conversion systems work - I design the software for them for a living.
> What you are basing your mental model on is an optimization for the
> case where the system is both sub-sampling the signal and going
> digital in the same operation. However, in many extremely high sample
> rate systems, the signal is brought down to baseband by mixing it with
> analog quadrature signals - that's the place where I and Q come from -
> and I assure you the only "delay by 90 degrees" is in the creation of
> the quadrature LO signals, not in the sampling of the actual data. But
> I've been around the Sun enough times to know that since you have
> decided upon this course and don't seem to want to change, there's no
> point in continuing to try to help.


As mentioned, the goal here is to explain I/q sampling in 5 minutes to a
group of average hams (i.e. who have limited knowledge of advanced
electronics and even less of math).
The question to answer is this:
what is i/q sampling and why does it it matters for him/her when
creating a GNU Radio flowgraph.


So, you do not have to convince me how i/q sampling works, you have to
convince this audience.


So, feel free to explain in semi-tech (no math) talk in 5 minutes *why*
SDR uses i/q sampling.
What is the PURPOSE of i/q sampling?



73
kristoff - ON1ARF