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
