Noisy constellation Output

addis_a · August 21, 2014, 5:12pm

Hi,

I am new to GNU Radio but have noticed something… When I create a PSK
modulated signal and output that to a constellation sink, why is the
signal so noisy? Why is the signal not in four perfect constellation
points?

Signal Source -> PSK Mod -> Constellation Sink

Thanks,
Luke

PEEL_Luke · August 21, 2014, 5:21pm

On Thu, Aug 21, 2014 at 11:11 AM, PEEL Luke
[email protected]
wrote:

Signal Source → PSK Mod → Constellation Sink

Thanks,

Luke

That’s ISI (inter-symbol interference) due to the transmit pulse shaping
filter. The last of our new tutorials (still in beta) covers these
issues:

http://gnuradio.org/redmine/projects/gnuradio/wiki/Guided_Tutorial_PSK_Demodulation

Tom