Take a $12 dollar
, available from Tony Parks, KB9YIG, and turn your
old ham rig
into a new one with all the DSP demodulators and features of a new rig.
I did it with my Kenwood TS-850SAT. Hooking the the Softrock between
the third IF (455 KHz) and the audio card on my shack computer was
quite easy. Most of the work was in software, but that was easier
because I could build on the work of Bob McGwier, N4HY, Frank Brickle,
AB2KT, and Edson Pereira, PU1JTE, N1VTN, JF1AFN. Now you can modify the
software further for your rig, if you choose. It should work on Linux,
Mac, and Windows, though I have only tested it on Ubuntu Linux.
picked the third IF for the connection point, because I
keep using all the 455 KHz filters I have installed. The TS-850SAT
allows you to independently select the filters in each IF, so I can
disable all but the 12 KHz roofing and third IF filters. This allows me
to have about 12 KHz of spectrum displayed if I desire. Others before
me had already determined the modifications to move the Softrock40 to a
455 KHz receive frequency. Tony sent me the 455 KHz kit very quickly,
such an astounding price. After taking my time building the kit, I
hooked it up as follows.
didn't want to affect
the normal operation of the TS-850SAT with this
modification, so I very lightly coupled to the third IF by connecting a
27K resistor to the junction of R109 and C83. The other end went to the
center conductor of the antenna input of the Softrock. See
which came from pages 144 and 147 of the TS-850SAT Service Manual. The
schematics for the Softrock can be found here. This worked out well,
because signals in the third IF were already much larger than needed by
diagram showing where to connect the 27K resistor that goes to the
input of the Softrock.
showing where the 27K coupling resistor
is soldered on.
I grabbed power from RX8, on the
TS-850SAT, the 8 volt line that goes high during receive. See
the photo below.
getting the hardware
going, I used Synaptic to get the lowlatency kernel and then used
Roger Rehr's web page
and Debian package
to get Dttsp and
SDR-Shell running on my Ubuntu Feisty box. The shell script, sdr, had
to be modified a little, and I learned a lot about how the Dttsp system
works with fifos and Jack Audio Connection Kit by reading the shell
script and bothering the experts on the dttsp-linux mailing list.
results are very nice. I really like the synchronous AM
for SWLing, and the automatic notch filter to get rid of tuner uppers,
and the binaural setting is really something to listen to.
are still things to work on, but that is the fun of ham radio.
Download SDR-Shell with IF Mods here.
Download the revised SDR-Shell (version 3a) Alpha Software here.
Download the revised sdr shell script for starting Dttsp and
Put sdr.sh in the directory /usr/local/bin/ and call it sdr.
> sudo cp sdr.sh /usr/local/bin/sdr
I had to fix several bugs in hamlib and add some features to
this software work properly. You need to download a snapshot
hamlib after 8/21/2007 here
software uses the usual Linux build system. To install
see the instructions here. You will need CXX bindings so that
C++ in SDR-Shell will work. The other bindings are optional.
Be sure to install a version that is later than August 21,
as I made significant bug fixes and improvements to make the IF version
of SDR-Shell work with my Kenwood. You must have the developer QT3
installed with multiple threads (I haven't tried QT4), and
your QTDIR environment variable must point to it.
can untar SDR-Shell with the command:
> tar -xvf sdrshell-3a.tar.gz
need to connect to the new directory you created.
> cd sdrshell/
Then you need to use QT.
> qmake sdr-shell.pro
and then copy it to a bin directory in your path
> cp sdr-shell /usr/local/bin/
and then you can run
sdr-shell with the command:
before you do that, you need to start dttsp, the signal processing
software for the demodulators. To do that you execute the sdr
shell script. As it stands you need to do that with root
privileges, like this:
> sudo sdr start
start command starts dttsp and connects the fifos up. You
should hear some noise coming out of your speakers if all is working
now. If so you are ready to start sdr-shell with:
> sdr shell
To stop the radio, quit sdr-shell from its
GUI and issue the command:
> sudo sdr stop
you don't like using root privileges and entering your password all the
time to start sdr, you can make the following changes to your system.
> sudo su -c 'echo @audio - rtprio 99 >> /etc/security/limits.conf'
allows you to run jack at the high priority needed for use with the low
latency kernel. With this changes you should be able to start sdr
with the following command:
> sdr start
and likewise stop it with:
> sdr stop
I hope this isn't too hard to follow. Let me know if you have questions.