Re: Combined constellation modulator/Decoder do not seem to work

[George Edwards]

Hi Mike,

Thanks for your help!

As I mentioned in my email, my flowgraph consists of some of the blocks in the example. I dropped some of the blocks because I am doing concept testing to ensure I know how to set parameters for the blocks. In terms of delays, that is not a problem. I am dumping the outputs into 2- file sinks, so in post processing I can compensate for that. The problem is that the tx and rx data are not the same, so I am missing in setting parameters.

Thanks again!

George

On Fri, Mar 12, 2021 at 3:31 PM Mike Markowski <mike.ab3ap@gmail.com> wrote:

I can't make out details in your image, George, but attach one I made
when working through the tutorial and works just now under gnuradio
3.8.1.0.  Like someone else mentioned in another reply, I found the
delay to be 58 and set it as the default in the attached flowgraph.
Zoom in on the bit stream plot and allow a second or two after changing
delay to see the effect.

Hope this helps,
Mike Markowski

On 3/12/21 10:37 AM, George Edwards wrote:
> Hello,
>
> I cannot get the combined Constellation Modulator/Decoder as shown below
> to work. The figure below is an example from the online Guided Tutorial
> PSK Demodulation.... I leave out the Equalizer, Costas Loop blocks, the
> channel was set to pass the signal unimpaired and the Poly Clock Sync
> was set for Output sps=1. The constellation plot of the output of the
> Poly Clock Sync is perfect. Now, in the flowgraph below, the signal
> entering the Constellation Modulator and that leaving the Constellation
> Decoder are routed into Time Sinks for display. I route these signals
> into File Sinks so I can print them and compare 1's and 0's. The results
> show they are not the same. I passed Constellation Rect.Object
> parameters to both the Constellation Modulator and Decoder, which seems
> logical to me, but I could be wrong???
> Will appreciate any help you can provide because what enters the
> modulator should be the same as what is leaving the demodulator.
> Regards,
> George
>
> image.png