SNR > reports 3 dB lower than actually present in the signal path.
Unfortunately s/n levels are not that simple to determine or set
, the original ROS , later Opera mode's where aligned with FLDIGI
to give the same results .
After a set of test run in the US , using Path-sim , it was felt , the
levels obtained where more realistic , and to enable better
comparative testing , the s/n displayed was re-calibrated
The Path-Sim software propagation simulator , which has a different
set of parameters and gives a different level is now used as the
reference.
Its important to understand that the two modes . will never , give
the same readings as wspr indicates the PEAK level , where Op
indicates the AVERAGE s/n , wspr is aligned with FLDIGI and over a
real path , the Op system is able to make use of deep variations in
fading and is immure to phase and Doppler distortion.
But , 'the eating of the pudding is in the proof of the making' ?
Stefan , last night reaching ua0aet over land , with 7 dB left in the
system, taking some big bites out of the distance records on 136
23:14 136 DK7FC de UA0AET Op32 5330 km -32 dB in Krasnoyarsk
73-G.
--------------------------------------------------
From: "Sabine Cremer" <[email protected]>
Sent: Wednesday, September 12, 2012 8:46 AM
To: <[email protected]>
Subject: 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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