Help QAM

GNU Radio
1

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?

  3. How do I setup a QAM-Demod module to produce an output? I don’t seem
    to get anything out that resembles the input.

Thanks…Tom

2

On 07/11/2013 02:10 PM, tom sutherland wrote:

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