======================
FREEDV GUI USER MANUAL
======================

Introduction
------------

This document describes additional features in the latest FreeDV
releases that haven't been documented in other sources.  See also
freedv.org

PTT Configuration
-----------------

Tools-PTT Dialog

Hamlib comes with a default serial rate for each radio.  If your radio
has a different serial rate change the Serial Rate drop down box to
match your radio.

When "Test" is pressed, the "Serial Params" field is populated and
displayed.  This will help track down any mis-matches between Hamlib
and your radio.

Voice Keyer
-----------

Voice Keyer Button on Front Page
Options-PTT Dialog

Puts FreeDV and your radio into transmit, reads a wave file of your
voice to call CQ, then switches to receive to see if anyone is
replying.  If you press space bar the voice keyer stops.  If a signal
with a valid sync is received for a few seconds the voice keyer stops.

Options-PTT dialog can be used to select the wave file, set the Rx
delay, and number of times the tx/rx cycle repeats.

The wave file for the voice keyer should be in 8kHz mono 16 bit sample
form.  Use a free application such as Audacity to convert a file you
have recorded to this format.

Test Frame Histogram
--------------------

Test Frame Histogram tab on Front Page

Displays BER of each carrier when in "test frame" mode.  As each QPSK
carrier has 2 bits there are 2*Nc histogram points.

Ideally all carriers will have about the same BER (+/- 20% after 5000
total bit errors).  However problems can occur with filtering in the
tx path.  If one carrier has less power, then it will have a higher
BER.  The errors in this carrier will tend to dominate overall
BER. For example if one carrier is attenuated due to SSB filter ripple
in the tx path then the BER on that carrier will be higher.  This is
bad news for DV.

Suggested usage: 

i) Transmit FreeDV in test frame mode.  Use a 2nd rx (or
get a friend) to monitor your rx signal with FreeDV in test frame
mode.  

ii) Adjust your rx SNR to get a BER of a few % (e.g. reduce tx
power, use a short antenna for the rx, point your beam away, adjust rx
RF gain).  

iii) Monitor the error histogram for a few minutes, until you
have say 5000 total bit errors.  You have a problem if the BER of any
carrier is more than 20% different from the rest.

A typical issue will be one carrier at 1.0, the others at 0.5,
indicating the poorer carrier BER is twice the larger.

Full Duplex Testing with loopback
---------------------------------

Options - Half Duplex check box

FreeDV GUI can operate in full duplex mode which is useful for
development of listening to your own FreeDV signal as only one PC is
required.  Normal operation is half duplex.

Tx and Rx signals can be looped back via an analog connection between
the sound cards.

On Linux, using the Alsa loopback module:

  $ sudo modprobe snd-aloop
  $ ./freedv

  In Tools - Audio Config - Receive Tab  - From Radio select -> Loopback: Loopback PCM (hw:1,0)
                          - Transmit Tab - To Radio select   -> Loopback: Loopback PCM (hw:1,1)

TODO
----

[ ] Merge this information into existing start up guides

