I’m trying to become familiar with gnuradio, starting with grc, but I’ve
run into a couple of stumbling blocks.
I’m using a USRP1 with an assortment of daughter boards, including LF-HF
and VHF capabilities. I’d like to be able to sample the spectrum in
relatively small segments, and capture the sample to a file, for
particular
amplitude exceedances. To be specific, I’m looking at lightning impulses
and attempting to capture narrow segments of its discharge spectrum for
analysis. Most of this will be below 100 khz, although I’m interested in
systematically sampling from 10khz to 1 MHz. Of I can capture sufficient
samples, I’ll perform wavelet and FFT analyses against them, to see if I
can identify patterns.
Could someone spare a clue to a new guy, and point me either toward an
appropriate starting point in Python, or a good place to start in a grc
flowgraph?
It will probably take a bunch of experimentation to find something that
works. Since you’re probably interested in the very beginning of the
signal, you’ll need to do power detection in parallel with a delayed
version of the signal so you trigger in time. Look up some of the
following blocks:
Delay
RMS
Burst Tagger
Tagged File Sink
Since you’re capturing fairly short events, try recording bursts at full
capture bandwidth (e.g., 1 MHz) to files, then do post processing as a
second step. Find or make up some test signals to feed your flowgraph so
you can work on it in good weather.
–
Gerry Creager
NSSL/CIMMS
405.325.6371
++++++++++++++++++++++
“Big whorls have little whorls,
That feed on their velocity;
And little whorls have lesser whorls,
And so on to viscosity.”
Lewis Fry Richardson (1881-1953)
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