Date: Sat, 9 Feb 2019 10:16:01 -0500
From: "John Langner WB2OSZ"
To: <wsjt-devel@lists.sourceforge.net>
Subject: [wsjt-devel] Generic Interface for DDS transmitter.
A local group is designing a homebrew transceiver as a group project. One
of the requirements is the ability to transmit WSJT-X modes. It will not
have SSB transmit so we can't use the usual transmit audio signal. Instead
we will be driving a direct digital synthesis (DDS) chip to generate the RF
directly.
We already have a proof of concept working with a Raspberry Pi and a DDS
eval board. A modified version of WSJT-X generates a UDP packet at the
beginning of each transmission. This contains information such as the
lowest tone, tone spacing, time for each symbol, and a list of symbol
values. A separate converter listens for the UDP packet, parses the
content, and commands the DDS chip to generate the different frequencies
with the correct timing.
A quick search of the wsjt-devel archives reveals that others have been
interested in a similar capability.
https://sourceforge.net/p/wsjt/mailm...sage/33465468/
https://sourceforge.net/p/wsjt/mailm...sage/32575984/
https://sourceforge.net/p/wsjt/mailm...sage/36416210/
This is what we have so far:
https://github.com/wb2osz/technightradio
Eventually we would like to get this capability into the official releasen
so we don't always have to use our own hacked version of WSJT-X. This
would also be useful to other people. A frequency agile WSPR beacon
transmitter could be built for a very low cost.
The current modifications are not ready to be added to the official WSJT-X
release. It spits out debug messages and there are still a few details to
work out. At this point, we would just like to get the conversation
started and get feedback from others. After some discussion, and more
refinement of the code modifications, we will submit a final version for
your consideration.
73,
John WB2OSZ