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..
>
