Hi Jim
I tended to see a better print from the wider system, but the propagation
changed over the test, your original signal was quite audible from the loud
speaker, in fact , would of been enough for a ssb contact !. both systems
appeared to print into the noise , this is a unnerving feature of the mode
, clear type from nowhere !
I'm not sure on the tone v bandwidth pay off, but a email to the code group
may get a outline ?
Simon Brown's drm780 has in the olivia mode a layered software search,
that when enabled, array processes the recovered audio file and detects an
olivia signal, giving the frequency offset and will apply this to the tx .
I'm not sure if it will detect the mode but may well do.
Best would test would to simply run the two systems in parallel as the peak
power required is not high to ensure reasonable decodes /
Interesting night !
Graham,..
--------------------------------------------------
From: "James Moritz" <[email protected]>
Sent: Saturday, January 03, 2009 1:36 AM
To: <[email protected]>
Subject: LF: Re: Olivia QSO
Dear Graham, LF Group,
Thanks for our first QSO this evening. As keyboard-to-keyboard "chat"
modes
go, this has to be the best I have experienced so far at LF/MF. The 32
tone/1kHz sub-mode produced almost 100% copy provided the signal was
audible - the somewhat slower 4 tone/250Hz setting was better still, only
producing errors during short periods at the fading minima when the signal
was completely inaudible and invisible on the spectrogram as well. I have
always struggled to copy G0NDB before, but on this occasion we had a
fairly
lengthy QSO without any great difficulty. I think the main practical
difficulty for random QSOs would be knowing that there was a signal
present
to decode - it would be sensible to have a calling frequency for future
tests.
I would agree that the 1kHz bandwidth sub-mode is too wide for routine use
in the present 500kHz band. But it does not violate the present licence
conditions, and I think it is an interesting experiment to see if a
relatively wide-band mode is an advantage for selective fading conditions
on
this band. Looking at the various menus in Fldigi, I see that Olivia can
be
configured for any combination of bandwidth from 125Hz to 2kHz, and 2 -
256
tones (I tried it - you can have 256 tones and 125Hz, or 2 tones in 2kHz,
although how well it works is another matter...). It would be interesting
to
try back-to-back comparisons with varying parameters to test the
possibilities of fast vs. slow, wide vs. narrow.
Cheers, Jim moritz
73 de M0BMU
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