# Copyright 2016 Ron Economos
#
# This file is part of gr-cessb
#
# gr-cessb is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 3, or (at your option)
# any later version.
#
# gr-cessb is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with gr-cessb; see the file COPYING.  If not, write to
# the Free Software Foundation, Inc., 51 Franklin Street,
# Boston, MA 02110-1301, USA.

gr-cessb
======

Author: Ron Economos
Email: <w6rz@comcast.net>

The goal of this project is to build a software-defined SSB transmitter
that implements Controlled Envelope SSB processing. It is based on this
article by David L. Hershberger, W9GR.

http://www.arrl.org/files/file/QEX_Next_Issue/2014/Nov-Dec_2014/Hershberger_QEX_11_14.pdf

After installation, two GNU Radio blocks called "Magnitude Clipper"
and "Peak Stretcher" will be available in the "CESSB" category. The
"Magnitude Clipper" block clips the magnitude of IQ samples to the
specified clipping level. It is the first stage of the CESSB algorithm.
The "Peak Stretcher" block does additional clipping. It is the second
stage of the CESSB algorithm.

There is one parameter for the Magnitude Clipper block.

1) Clipping Level. The magnitude that IQ samples will be clipped to.

A GNU Radio Companion flow graph (ssb.grc) is provided in the apps
directory. It transmits a test file (ssbaudioprocessed.wav) with a
UHD sink setup for an Ettus B2X0 SDR. Be sure to select the correct
sink for your device.

The test file is a male announcer reciting a portion of the Gettysburg
Address. It has been processed from the file ssbaudio.wav with the sox
command:

sox ssbaudio.wav -b 16 ssbaudioprocessed.wav compand 0.0,0.01 0.25:-20,-20,0,-20 -0.1 -40 .0005 gain -n -3.0102999566

The sox sound processing utility is available here:

http://sox.sourceforge.net/

Build instructions:

    mkdir build
    cd build
    cmake ../
    make
    sudo make install
    sudo ldconfig

Contributions are welcome!