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Re: [Discuss-gnuradio] help QAM
From: |
Josh Blum |
Subject: |
Re: [Discuss-gnuradio] help QAM |
Date: |
Thu, 11 Jul 2013 19:34:32 -0400 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130623 Thunderbird/17.0.7 |
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