I've been working on a new FreeDV 700E mode, and some compression for
FreeDV 700D and 700E to increase the average power. A Christmas present
for you to play with
700E is designed to handle fast fading like 700C, but like 700D has
powerful FEC. My bench tests indicate 700C & E are equivalent on
moderate fading channels (2Hz dopdler/2ms spread), but on very fast
fading (4Hz/4ms) 700E does better - 700C & D fall over. 700D works
better at lower SNRs on slow fading channels.
I've also been testing against compressed SSB, which as Helmut suggests
is pretty hard to beat, as it's so robust to fading. However 700E is
hanging on quite well with fast fading, and becomes noise free as the
SNR increases.
-/-
The second innovation is compression of the 700C/D/E waveforms, to
increase average power significantly.
Please be careful adjusting the Tx drive and especially enabling the
Tool - Options - Clipping. It can drive your PA quite hard. I have
managed 40W RMS out of my 75W PEP transmitter. Make sure your
transmitter can handle long periods of high average power. My IC7200 and
FT-817 seem OK.
At the same equivalent peak power - 700D is doing well when compressed
SSB is -5dB SNR and rather hard on the ears.
-/-
Peter VK3RV, Jose LU5DKI, and Barry VK3BRT tried 1.5.0 last night and
report it works on real HF channels.
The latest manual describes the new features:
https://github.com/drowe67/freedv-gui/blob/118cb66ee4679518185db871ec0ae68071c406a4/USER_MANUAL.md
You can download Windows 32 and 64 bit versions of FreeDV 1.5 here:
http://rowetel.com/downloads/freedv
-/-
I'd be interested in any feedback. If you have an interesting test case
(e.g. a bug or comparing SSB to FreeDV), pls send me off air recordings
of signals (FreeDV Tools-Record File from Radio). That helps me make
objective comparisons. Recordings are much more useful to me than
anecdotes or subjective reports.
Thanks,
David
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