Re: [Discuss-gnuradio] Simple QAM project

[Tom Rondeau]

On Sun, Jul 7, 2013 at 5:50 PM, tom sutherland <address@hidden> wrote:
> I am new to linux and GNURadio.  I don'g follow where the 1 bit/byte is
> coming from. Does the audio source not deliver 8bit/sample or how do you
> figure that out? I don't see anything such as
> "gnuradio>digital>generic_mod_demod.py " in my directories. Thanks for the
> help.
> Tom

Tom,
The audio source will produce single-precision floating-point samples
between -1 and 1. You'll need to think about how you want to convert
these to digital samples that the QAM modulation can handle. So first
convert it into some quantized representation (i.e., as fixed point).
Then, you should have a stream of 'packet' bits that can be directly
inputted into the modulator.

There are blocks called packed_to_unpacked / unpacked_to_packed as
well as a unpack_k_bits / pack_k_bits that you can use to go from
unpacked to packed representation.

Tom



> ------------------------------------------------------------------------------------------------------------------------------
> Tom,
>
> There are few changes required in ur FG
>   1: PSK/QAM Modulator takes packed byte input (8 bits per byte) instead of
> 1 bit per byte
>                see gnuradio>digital>generic_mod_demod.py
>   2: Constellation sink work only for PSK modulation M=2,4,8.
>
> To see output constellation of QAM-16 u will have to first downsample it to
> 1 sample_per_symbol and then use wx-scope-sink in XY-Mode
> Down-sampling can be done using symbol-timing blocks or manually
> (delay+keep1inN combination) as in attached FG
>
> -Adeel
>
> ________________________________
> From: Adeel Anwar <address@hidden>
> To: tom sutherland <address@hidden>; address@hidden
> Sent: Friday, July 5, 2013 10:25 PM
> Subject: Re: [Discuss-gnuradio] Simple QAM project
>
>
> Can u attach ur GRC file?
>
> -Adeel
>
>
> On Fri, Jul 5, 2013 at 5:48 AM, tom sutherland <address@hidden>
> wrote:
>
> I am trying to get data through a QAM-16 Modulator and just display the data
> stream on a Constellation Sink. I have 8khz sampled 8-bit data(char) going
> into the QAM Mod block. I have the output of the QAMmod block going directly
> into the Const Sink. I am not seeing anything on the Constellation Sink. I
> put a throttle block in but that didn't help.
> Any thoughts on what could be wrong? I have followed the GNUradio tutorial:
> Part 4 by balint256 but didn't help.
> Thanks...DT
>
>
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