Hi David and Glen,
> On 07/05/18 07:45, glen english wrote:
> > SSB sometimes wins because the brain picks up the slack. like with a 0.5
> > second fade.
On listening to FreeDV 700D and DMR, one's brain recognises this "new" accent
and processes
accordingly. I don't think you can say, definitely SSB wins.
After Mark VK5QI and I went to "normal" SSB, we had difficulty in copying each
other.
So, at this point, 700D and SSB are about neck-a-neck.
One point I see as missed. We HAMs are not allowed encryption but this new
encoding
gives hams in Emergency communications a far more secure communications method.
It's like the tapes CBA lost track of.
1) They are probably LTO tapes of 800Gb capacity or more. Who has a tape-drive
to read them?
2) The tape drives do encryption!!!!!! Who has the key. (Drive encryption was
available in 2008!!!!)
3) The software to "unpack" the data on the tape??????? Tivolli Storage Manager
etc...
Good luck to those with the tapes.
Thanks David for all your hard work.
Yes, I have done some C programming, only really basic stuff.
Alan VK2ZIW
On Mon, 7 May 2018 08:32:58 +0930, David Rowe wrote
> The 700D waveform is designed for subset of those paths. As part of
> the testing I'd like to crowd source some samples of where it works
> and were it doesn't.
>
> Long term - if the average SNR is there, a waveform can be designed
> to pass DV over it. Eventually.
>
> DV over HF is a tough problem, and every development consumes 1000's
> of volunteer man-hours (mainly mine). So I'm taking a tractable
> path through the problem.
>
> Currently the focus is on low SNR HF channels. I'll make
> incremental improvements from there, e.g. rarer HF paths, higher
> speech quality at higher SNRs etc.
>
> - David
>
> On 07/05/18 07:45, glen english wrote:
> > SSB sometimes wins because the brain picks up the slack. like with a 0.5
> > second fade.
> >
> > In my opinion, for HF paths, to be broadly useful , voice DV modes need
> > to pass an HF fading simulator, targeted at vertical incidence work, and
> > bear in mind, that the channel profiles are quite different for
> > Equatorial, Mid latitude and high latitude locations. And they must have
> > minimal conversational delay, , < 0.25 seconds.
> >
> > take a look at
> >
> > https://www.itu.int/dms_pubrec/itu-r/rec/f/R-REC-F.1487-0-200005-I!!PDF-
E.pdf
> >
> >
> > several languages :
> >
> > https://www.itu.int/rec/R-REC-F.1487-0-200005-I/en
> >
> >
> >
> > This article, is useful for its 127 excellent references,
> > https://link.springer.com/article/10.1007/s11235-017-0287-2#CR38
> >
> > and has some excellent channel profile references .
> >
> >
> > From the DRM spec, Annex B Definition of channel profiles
> > Channel 6, path 4
> > delta delay : 6mS, path gain RMS = 0.0625, dopplershift : 3.6Hz, dopper
> > spread 7.2Hz
> >
> > Some paths are worse than that .. especially vertical incidence paths
> > what have values almost triple the above numbers....
> >
> >
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