On 03/06/2015 10:12 AM, Marcus Müller wrote:
Hi Activecat,
I still don't understand; do you really just want a offline data
periodogram?
In that case, have a look at the python "matplotlib" library examples.
Also, Martin's and Lou's statements still stand: just by labeling an
axis dBm doesn't make the data actually represent that physical entity.
Greetings,
Marcus
On 03/06/2015 02:54 PM, Activecat wrote:
Thanks for the answers. Let me further elaborate.
I could get what I want using Matlab, via below steps:
_______________________________________________
Discuss-gnuradio mailing list
Discuss-gnuradio@gnu.org
https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
So, I think what is wanted is some version of:
signal--->window-->FFT--->scaling-of-some-sort(both linear and
non-linear)--->average--->display
GR can do all of those things, and the FFT "instrumentation" widgets are
a version of the above.
But as several have pointed out, and I'm about to repeat, without
*calibration* you only know what the results mean in a *relative*
sense. The
instantaneous voltages as seen by the ADC have been manipulated by
all the analog "goo" in front of the ADC, including amounts of gain that
aren't precisely known. Further, the ADC *output* is filtered (via
decimation) before you see it, which should be a largely-linear
operation, but you
don't know the exact gain of that transform. So, the only way to get
precise numbers in dBm/Hz is to use laboratory calibration measurements so
that you can refer this to "at the plane of the antenna connector".
That's the only reasonable way, and it's the way that laboratory grade
things
like spectrum analyzers deliver fairly-precise numbers--not because
of mathematical "tricks", but because they are *calibrated, regularly*
against
calibration standards.
_______________________________________________
Discuss-gnuradio mailing list
Discuss-gnuradio@gnu.org
https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
