Hi all,
I've been listening and transmitting on 7177KHz LSB but hear
nobody.
14150 and 14153 both have interference here so I've occasionally
tried
on 14236KHz but again nothing.
I've "asked" on VKLOGGER and AHRDF. It seems there's all but nobody
willing to compile the sourcecode and run it except Mark VK5QI and
me.
http://ahrdf.net/ and http://www.vklogger.com/
Does this show, just how few hams have Linux expertise?
I have not switched on a Windoze box for months, no need.
Anyway, I'm looking forward to some on-air tests.
No 73 valves here, nearest here a 6BK4.
Alan VK2ZIW
On Mon, 7 May 2018 13:50:17 +0200, Helmut Oeller wrote
Hi Glen,
very interesting paper! Thanks for sharing the link. Yes, I agree
that a realible 'simulator' providing the real world of a HF
channel
would be very helpful to compare communication modes. Man-made
noise
caused by PLC or SMPS etc. is another challenge especially on HF
bands. Before I'll stop my laudation for the 'old' SSB another
example what advanced DSP algorithms can effect in bad man-made
noise enviroment:
https://www.dropbox.com/s/wt32pepaurnbvbq/W5WC_NB%2CSNB%2CNR2_OFF
.mp3?dl=0
https://www.dropbox.com/s/tubqmidw4bor265/W5WC_NB%2CSNB%2CNR2_ON.mp
3?dl=0
Hopefully nobody feels offended by my lanky posts, but after more
than 50 years with activity on the commercial side of
communications
I think that I earned a ticket for my point of view.
73, Helmut, DC6NY
-----Ursprüngliche Nachricht-----
Von: glen english <g...@cortexrf.com.au>
Gesendet: Montag, 7. Mai 2018 01:42
An: freetel-codec2@lists.sourceforge.net
Betreff: Re: [Freetel-codec2] 700D vs SSB Comparison
Hi David
fair enough
here is some good and reasonable recent work by one of your
own.....
http://search.ror.unisa.edu.au/record/UNISA_ALMA11140739050001831/m
edia/digita
l/open/9916110811201831/12140739040001831/13140739030001831/pdf
Maybe build into freeDV some sort of recording to disk and FTP
upload to codec2 server....
On 7/05/2018 9:02 AM, 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.1487-0-200
005-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#C
R38
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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Evil flourishes when good men do nothing.
Consider the Christmas child.
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