Re: [Discuss-gnuradio] help QAM

[Josh Blum]

On 07/11/2013 02:10 PM, tom sutherland wrote:
> I have a simple 16QAM project. I want to do audio but for right now I 
> have a signal source "constant"  input to the QAM module. I am trying to 
> display the constellation diagram but it's not displaying what I think 
> it should. I have a few questions....
> 1) I would think that inputing a constant value into the QAM module would 
> produce a single point, it doesn't, it puts up a grouping of 8 points of the 
> 16 possible locations. I am trying to verify the input verses 
> output.
> 
> 2) The QAM module expects a "char" type which I assume is 4 bits. If I 
> have 8-bit (byte) data from a audio source, how do I feed the QAM 
> module?
> 

I think this will help. Many of the modulators in gnuradio take byte
inputs where each byte is fully packed with data. In other words, each
byte != one symbol. The modulator chain actually unpacks the byte into
symbols. Perhaps this explains 1 and 2.

-josh