Hello Sabine,
as mentioned in the report the test were done off-air, by adding equal amounts
of pure white noise to WSPR / Opera signals of identical amplitude.
So no QRM/QRN or QSB involved. Maybe I will do these tests over with QRN and/or
QSB added (if there is some interest and if time permits).
In these tests WSPR performed 7dB better than Opera2. 3dB can be explained by
the fact that WSPR is a 100% duty cycle mode while for Opera it is only 50% (or
said otherwise: WSPR = FM and Opera = AM). The remaining 4dB could be due to
different coding /decoding algoritms. WSPR coding and protocol is public source
(http://physics.princeton.edu/pulsar/K1JT/WSPR_2.0_User.pdf), for Opera it is
"cracked" by PE1NNZ (http://rn3aus.narod.ru/opera_protocol.pdf).
73, Rik ON7YD - OR7T
________________________________________
Van: [email protected] [[email protected]]
namens Sabine Cremer [[email protected]]
Verzonden: woensdag 12 september 2012 9:46
To: [email protected]
Onderwerp: LF: RE: [rsgb_lf_group] Re: LF: slow WSPR?
Hi Rik,
thank you very much for the link to the results of your study.
I was told often, that Opera is much more sensitive than WSPR. It was
interesting to learn that this might be the result of Opera giving SNR
reports 3 dB lower than actually present in the signal path.
I think, there are some myths surrounding some digital modes... ;-)
73
Sabine
Am 12.09.2012 08:55, schrieb Rik Strobbe:
> Hi Marcus, Stefan, All,
>
> Some kind of "WSPR8" (8 minutes wspr sequence) could indeed be tested
> by generating the WSPR8 signal (what is easy as WSPR is fully
> documented) and accelerate the recorded signal 4 times before feeding
> it into the WSPR software. But this method requires to reduce the
> WSPR8 bandwidth (frequency spacing between the tones) also by a
> factor
> of 4, from 6Hz to 1.5Hz.
>
> If you look at WSPR as an FM signal, the WSPR8 signal created that
> way will have the same modulation index as the original WSPR(2)
> signal, while a WSPR8 signal at the "old" 6Hz bandwidth would have a
> 4
> times larger modulation index. And the modulation index affects the
> SNR. Thus the suggested method might not fully exploit the
> possibilities of WSPR8 (at unchanged bandwidth).
>
> BTW: the results of the SNR performance test are still available at
> http://on7yd.strobbe.eu [1]/QRSS/ [1].
>
> 73, Rik ON7YD
>
> -------------------------
>
> VAN: [email protected]
> [[email protected]] namens Markus Vester
> [[email protected]]
> VERZONDEN: dinsdag 11 september 2012 19:41
> TO: [email protected]
> CC: [email protected];
> [email protected]
> ONDERWERP: [rsgb_lf_group] Re: LF: slow WSPR?
>
> 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..
>
>>
>
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