Hello
A group of us working with Gnuradio to build home radio telescopes has
been working for
a few years with gnu radio. The code for our observations was in a
form that was
“orphaned” with changes to gnu radio.
The observing interface has been re-released (in an improved form) via
git hub. It can
be obtained with
git clone http://www.github.com/glangsto/gr-nsf
Despite lots of work, the result is only a few new blocks in a python
sub-directory
and .xml files in the “grc” sub-directory for use with with
gnuradio-companion (GRC).
The examples directory contains the .grc files to be run to make
observations.
The examples README.md has instructions.
The examples directory also has two .grc files that test the blocks and
show now problems on either Ubuntu or Mac OS.
We find an issue for this code an Ubuntu, that is not present for Mac
operations.
Using exactly the same code on Ubuntu shows the problem, while the mac
code does not.
We guess the problem is in some way associated with our use of the
Osmosdr block
and an AIRSPY mini.
The problem is that the spectrum has a weak alias relative to the
center of the band pass.
We’re hoping someone might have a suggestion on how to mitigate this
problem on Ubuntu.
An example spectrum showing the interface and the problem is attached.
For Radio astronomy the galactic hydrogen signal is near 1420.4 MHz ==
0 velocity. The alias signal is “folded”
to the lower half of the band. The green curve show the problem on
Ubuntu. The baby blue and red
signals were taken with the Mac and have no alias. The hot load (red)
was also taken with the Mac