This commit adds a hierarchical block that performs Doppler
compensation and resampling.
Rather than using directly the available Doppler correction blocks,
based on the user parameters of the incoming sampling rate and the
desired target sampling rate, it applies proper decimation on the signal
so the frequency shift to be applied to a smaller sampling rate,
reducing significantly the CPU resources required. At the previous
architecture (gr-satnogs 1.x.x) we used seperate blocks for the doppler
correction and the LO digital shift, operating at the device sampling rate.
These two blocks, performing almost the same operation, contributed to a
30% CPU usage of the overall application. Now the LO is compensated by
the Doppler correction block, taking into account at the same time the
Doppler drift.
After the digital LO shift, the Doppler corrected signal is passed through
an Polyphase Arbitrary Resampler, to match exactly the sampling rate
requested by the user.
This commit adds a inital METEOR flowgraph that can be used for
capturing raw IQ. The capturing is performed in a sampling rate of
320KSPS which is more than enough for actual decoding for both METEOR
modes (72K and 80K). Due to icnreased bandwidth no audio file is
generated.
All flowgraphs now support user defined parameters for most of their
configuration capabilities. These include:
* RF gain
* IF gain
* BB gain
* Custom device arguments for setups with multiple SDRs. These
coresponds to the 'Device arguments' field of the Osmocom source block.
* Antenna selection for devices with multiple antennas (USRPs, etc)
Changing sampling rate is not supported (yet).
For listing the arguments just execute <flowgraph> --help in a terminal
window.
In memory limited devices like RPi, the default buffer allocation scheme
of the RTL driver causes problems to the async transfer engine.
This prevented the flowgraphs to start.
Reducing the buffer size fixes this problem.
Taking out WBFM/NBFM for a straight quadrature demod method
Change from 44.1k output to 44k output to be more compatible
with gr-satellites
Also changing rtlsdr to a 2msps rate by default
* UDP Message source can handle multiple data types
* Add a waterfall sink block
* Fix dependency issues with VOLK
* Add mean and max hold mode to the waterfall sink
* Add mean and max hold mode to the waterfall sink
* Install satnogs_waterfall.gp gnuplot script at
<install_prefix>/share/satnogs/scripts
* Automatically retrieve x and y axis ranges at the satnogs_waterfall.gp
The FM demodulator now supports a variaty of hardware setups and saves
the WAV file for further processing. A set of command line arguments can
control most of the flowgraph internals, such as the wav file name and
storage path e.t.c.
TODO: Check the settings for all the available hardware
Manolis Surligas
Julien
Vasilis Tsiligiannis
surligas
Corey Shields
Manolis Surligas
George Vardakis
Sleepwalker