On 03/06/2018 10:32 AM, Langston, Glen wrote:
Dear Marcus,

Thanks for your efforts on spectra_radiometer.

I’m still pursuing the issues with alias spectra and linux,
but I did see the same alias problem with spectro_radiometer under linux.
I’ll download the latest version spectro_radiometer and produce the mac and linux comparision
plots in the near future (maybe tonight).

FYI the effect I’m seeing with “NSF watch” aka (watch.py) is shown by
comparison in the two attached screen captures.  Odriod shows the problem
and mac does not.

I’ve got to gather up the strength try to get my python code into GitHub.
The current way I install is just tar -xvf the latest tar file (attached),
cd into the directory and the type:

python watch.py

On Odroid I actually type

taskset -c 4,5,6,7 python watch.py

so as to use the fastest 4 of the 8 processors.
The odroid is able to eat all 6MHz bandwidth Airspy mini data
The kernel will migrate processes as they start to max out their respective CPU, so using "taskset" is generally not required.

Note my major change/improvement over what happens naturally
with the WxGUI FFT is to sum all of the FFTs that are passed
as messages.  The Gnuradio Wx Spectrum GUI only processes
the first of N messages in the packet.   For radio astronomy,
I’m averaging about 1.3 Million spectra per 4 minute observation.

I appreciate the way you’ve put all the configuration arguments on
the command line of spectro_radiometer.py.   My implementation
stores the all information needed to configure the entire observation
in each observing file.   (Note a data directory is created
parallel to the “watch” directory).
My approach to having a "config file" functionality is to wrap the "naked" .py in a shell script that can handle all of that.

I’d appreciate any suggestions you, or anyone, has.

Best regards

Since some needed packages are not automatically installed by gnu radio
(such as ephem, I’ve added “try” code with suggestions for installing
the likely packages)
I have done that in the past, and I tend to get sloppy about it. My odroid stuff I have total control over what's on the system image, so the corresponding GR flow-graphs don't need to care, because they "know" that ephem is "just there."

The attached plots show the observation of RFI found at 1440 MHz in
my vicinity.   The Linux gnu radio observations show the
problematic alias.  The data files have
date and time names with extensions:
.ast - astronomy
.hot - hot load calibration observations, usually pointing straight down (El = -90)
.not - configuration for observation setup.  (Notes==.not)
Occasionally I compute a cold load spectrum for full calibration:

Have you tried this on a Linux platform that isn't an Odroid? I'm thinking of numerical bugs in things like VOLK or the SIMD implementation or something like that.

But I haven't observed this imaging effect myself on any of my Odroid+AirSpy systems. Our dual-channel H1 spectrometer is AirSpyR2 + Odroid XU4 + Arch.
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