Hi Stefan, LF,
if I
remember correctly, Rik's careful evaluaton of SNR performance in
February resulted in a threshold for reliable decoding of -23 dB for
Opera-2, versus -29 dB for WSPR. This is carrier power versus noise in
2.5 kHz, Opera "average power" reports are scaled 4 dB lower. Thus at
same available ERP, WSPR would indeed have a 4x advantage in speed, and
be equivalent to Opera-8. WSPR also transmits slightly more
information, ie. locator field and power.
Rik
also looked at QRSS and DFCW, which at 100 % readability seemed to
provide same or slightly higher throughput than Opera (with some
depence on callsign length and viewing skills).
Technically
it would be straightforward to generate a slow WSPR transmission, and
also certainly feasible to play back an accelerated recording. You'd
have to get the timing right to fit to the 2-minute slots, and the web
reports would probably show wrong frequencies, times and SNR. As Roger
says, asking Joe Taylor for a modified version would be a better
permanent solution.
But
whether slow or fast, it' still a digital mode, containing a blackbox
producing either valid output or nothing at all. If you are after
detection of the weakest possible signals, in my opinion the visual
modes or even a straight carrier transmission will be the only way
to see those "T" and "M" traces, along with the features of the noise
or QRM which we are trying to overcome.
Best
73,
Markus
(DF6NM)
-----Ursprüngliche Mitteilung-----
Von: Stefan Schäfer <[email protected]>
An: rsgb_lf_group <[email protected]>
Cc: Edgar J Twining <[email protected]>
Verschickt: Di, 11 Sept 2012 1:14 am
Betreff: LF: slow WSPR?
It's a pity that there is no slow-WSPR, e.g. needing 32 minutes or so.
If WSPR (2 minutes FSK) is about as efficient as OP8 ( i heared so),
then it should be a real alternative to the slow DX modes on LF but not
on MF!
There is a software that plays recorded audio files in a faster mode, so
that QRSS becomes audible. VE2IQ has reported to me last year about it
but i don't remember the name.
Would it be possible to make our own slow WSPR by using that software
and playing a 32 minute manipulated WSPR at 16x speed, feeding it to the
normal WSPR rx software? The slower code could be generated outside the
program. Would that be a useful test or do i miss something?
73, Stefan/DK7FC
Am 10.09.2012 19:26, schrieb Graham:
> May be Mal
>
> But once again Jim has the answer to this problem ..if you can
> find his articles after Google trashed the uk500khz news group ,
>
> I think Jose R predicts a 6 dB gain by changing to PSK from
> the Opera on/off keying but that would prevent most of the
> LH/MF usage
>
> G..
>
