An appeal to datamode software authors...
Could anyone writing / contemplating any datamode software please consider
incorporating I/Q stereo outputs and inputs. With SDR receivers becoming
more widespread, I/Q audio inputs will allow direct use with simple receivers
such as Rocky and homebrew ones without having to loop into an SDR prog, back
out and into the datamode software.
Generating I/Q audio on transmit is probably even more valuable. Receivers
like the SDR IQ send a serial output which is just asking to be intercepted and
used to control a DDS/Synthesizer LO for an upconverter, turning these
receivers into point and click transceivers.
The whole amateur SDR area has quite naturally, so far, concentrated on receive
but its about time more attention was put into transceive operation. Having
I/Q audio drive ready and available is the simpler home-brewable solution.
At the moment at LF I've had to resort to making up all pass networks and
accepting the narrow band of useful operation and need for careful trimming for
good sideband rejection. See
http://www.g4jnt.com/IQConverters.htm
http://www.g4jnt.com/LFUpconv.pdf
Have just been through all the installed datamode packages on this machine and
the following
MMTTY, Digipan, IZ8BLY Hell, ROS 1.6.2, WSJT7, WSJT8 even G3PLX's PSK31SBW and
teh brand new CMSK all failed the test, giving an annoying pair of identical
sinewaves from left and right channels on the scope.
Only MultipPSK gave a nice pair of quadrature sinewaves on the audio drive,
so this comprehensive bit of software is my clear winner so far.
Datamodes intended for LF/VLF could be considered one of the more important
targets as commercial transceivers are hardly ever used here, and direct
I/Q upconverters are almost trivial at these frequencies.
Andy G4JNT
