I am using GNU Radio and I checked out out and built gr-rds.
However RDS Decoding is not working. I found that there are to two
connections have dashed lines (see picture). And in the terminal all I
get is Error: Cannot create connection. But I could not find a hint,
what is going wrong. Can somebody tell me, what to check for?

Best regards,

Hi Mike,

dashed only means “message port connection” rather than “item stream”,
so that’s nothing to worry about, usually.
So the bad news is that this is possible a GRC bug, which on the other
hand is good news, because it means that gr-rds isn’t broken, GRC just
has a hard time correctly generating the python file.
Since that worked for me: can you try the attached python file?

Best regards,

Hi Marcus,

thanks, tried your script and found out, that it is always a little bit
uncomely if something is not really reproducible. This is the status:

With your script I did not get the earlier error anymore. However with
my original I did not get it either. Instead I get the following message
in GRC:
@@@@@ Sync State Detected
@@@@@ Lost Sync (Got 50 bad blocks on 50 total)

I do not get this message if I run your script. Both scripts though do
not show RDS information. So before I steal somebody’s time I wonder if
one reason could be, that I can only receive one station really at the
limit and only if I set gain to a max. I can hear fairly clear audio,
but I am not sure if I can conclude from, that RDS decoding should work.
I am pretty much insulated from RF at my place. What would be in favor
by people being sensitive to EM waves, but for experimenting it is
pretty bad.

So I might gonna check this outside, where I can see in my car, that RDS
reception is working on my radio and then I can compare. Just want to
make sure we or you aren’t chasing an error which might be based on poor

However the messages in the terminal have been there last time and the I
copied to also were there. Still don’t no if this is part of the problem
though. Therefore probably more testing on my side.

Best regards,

Hi Michael,

i read your mail and i could remember i had a similar problem with a lot
of lost sync and bad block messages.

My solution was to use a different RTL USB stick and to play with
antenna type / antenna position and the gain of the RTL stick.

I used a “classical” lamda / 2 dipol UKW Radio antenna. The stick was a


Am 23.08.2015 um 20:02 schrieb Michael Thelen DK4MT:

Hi Mike,
the B200 should usually be a little more reliable than the RTL dongles;
what gain setting are you using?

Best regards,

Hi Marcus,

I hoped so, that is why I bought one ;-). I think the max is 73dB. The
actual value I set with a slider is 90dB. Thus I am pretty much maxed
out there. But like I wrote earlier, that is the only way to receive at
least one station. Don’t have good RF working conditions. Even cellular
is a problem.


Hi Andreas,

thanks for the hint. However I am using a Ettus B200 and do not have
access to a different SDR right now. I will test outside and then trying
to find out what is going on.


Hi Marcus,

I did some further testing. Took me some time unfortunately. The RDS
reception outside is slightly better. But I still got “Lost Sync” info
in the terminal window. However, I could see decoded information. I
can’t fight the feeling, that I am missing quite a bit of sensitivity. I
did some more testing with a flowgraph from the gr-gsm packet in the
apps directory. There must be BTSs out there ;-). But I could not see
anything. I used the Ettus Log-Per antenna.

I want to check the hardware and make sure everything is working
correctly. But I will move my question concerning the hardware to the
USPR-users mailing list.

Best regards,

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