# GNU Radio does not run flow graph

I am sorry but yet again a question about GNU Radio. (I just started following some tutorials a couple of months ago and am learning about it. I am unfortunately not that proficient in it yet, but I am getting there).

Background: So here at the end of the post is my (infamous) FM Receiver flow graph (my hello world in GNU Radio). Nothing has changed. Everything's still as it was (in my first two posts). In fact the problem appears independent of which flow graph I run (as long as it does not contain any bugs), no matter whether I use Qt GUI or WX GUI.

• I upgraded to Windows 10 and also updated to the latest binary (v3.7.13.5/v1.6) for GNU Radio from here.

Problem Observed: The problem is the flow graph appears to start, and stops immediately. No errors. The flow graph window appears, but all I see is the titlebar, and the close, minimize and maximize icons. The rest of the window never appears. The only output I see in the terminal window down in the bottom left corner is the following:

Terminal Log

<<< Welcome to GNU Radio Companion 3.7.13.5 >>>

Block paths:

>>> Done

>>> Done

>>> Done

built-in source types: file osmosdr fcd rtl rtl_tcp uhd hackrf bladerf airspy redpitaya
[INFO] [UHD] Win32; Microsoft Visual C++ version 14.0; Boost_106000; UHD_3.14.1.HEAD-0-g5491b80e

>>> Done


I also get a ton of warnings when launching the GNU Radio as shown below (I had to remove some lines here as I was hitting the post size limit):

Startup log

setting gnuradio environment
Warning: Block with key "acars2_decode" already exists.
....
*(a lot of similar lines -> I guess nearly all the blocks/modules in GNU Radio)*
....
Warning: Block with key "zeromq_sub_source" already exists.
<<< Welcome to GNU Radio Companion 3.7.13.5 >>>

1. I thought maybe it is some permissions problem. I tried launching GNU Radio as administrator (just to test).

• GNU Radio just failed to start.
2. Anyways, as always, the Dongle works. I compared it, by running CubicSDR.

3. After I had posted this question on HAM.SE, I downgraded to version 3.7.11.1 from here and it was able to launch the Flow graph.

• Even though, only Qt GUI worked. When a flow graph made with WX GUI is run, it would start a little and then the window would freeze. Which is strange. As with this GNU Radio version, this flowgraph used to work on Windows 8.1.
4. Then after @MarcusMüller hinted that I may possibly have two GNU Radio installations [possibly conflicting with each other],

• I removed the GNU Radio version 3.7.11.1,
• restarted the computer
• and thoroughly checked that there are no GNU Radio installations anywhere.
• I reinstalled the latest version of GNU Radio 3.7.13.5 and the same problematic behavior was observed as explained above.

What one can see though is that due to some reason (some setting or bug), this version 3.7.13.5 of GNU Radio includes the blockpath twice, as shown below.

<<< Welcome to GNU Radio Companion 3.7.13.5 >>>

Block paths:

>>> Done

>>> Done

>>> Done


And from there come all the warnings, I guess. (I have NOT made any such changes. The installation was done with default settings, just like for the other version of GNU Radio v3.7.11.1.

One of the (otherwise working) flowgraphs:

My tentative Conclusion: As far as I can see, the Windows build for GNU Radio v3.7.13.5/v1.6) is buggy here.

• that console output indicates multiple conflicting GNU Radio installations, which would explain all kinds of bugs, including random crashes. You need to remove one of your installations so that it doesn't interfere with the one you want to use. – Marcus Müller Aug 11 '19 at 12:36
• With your EDITs it's not clear whether you still have a question. Please rewrite your question so that it starts out explaining what you're currently asking and the sequence of troubleshooting events/observations is secondary. Don't use "EDIT". – Kevin Reid AG6YO Aug 11 '19 at 15:29
• @MarcusMüller That comment probably ought to be an answer. – Kevin Reid AG6YO Aug 11 '19 at 15:30
• @KevinReidAG6YO not quite sure – it's really just a suspicion, a request for OP to clarify by making sure there's only one installation – Marcus Müller Aug 11 '19 at 15:34
• @marcus müller, I had no other gnu radio installations when that happened. But I will check tomorrow morning once again to be sure. – Duck Dodgers Aug 11 '19 at 21:10

• thank you very much. :) I will try it at home tonight. – Duck Dodgers Sep 30 '19 at 6:53