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Date: Wed, 12 Sep 2012 15:35:43 +0200
From: Sabine Cremer <sabine@dl1dbc.net>
To: <rsgb_lf_group@blacksheep.org>
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Subject: Re: LF: RE: =?UTF-8?Q?=5Brsgb=5Flf=5Fgroup=5D=20Re=3A=20LF=3A=20s?=
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Thanks for the hints, Graham, I will try to keep all in my memory!

73
Sabine, DL1DBC


Am 12.09.2012 12:22, schrieb Graham:
> 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" <sabine@dl1dbc.net>
> Sent: Wednesday, September 12, 2012 8:46 AM
> To: <rsgb_lf_group@blacksheep.org>
> 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: rsgb_lf_group@yahoogroups.co.uk
>>> [rsgb_lf_group@yahoogroups.co.uk] namens Markus Vester
>>> [markusvester@aol.com]
>>>  VERZONDEN: dinsdag 11 september 2012 19:41
>>>  TO: rsgb_lf_group@blacksheep.org
>>>  CC: edgarjtwining@virginbroadband.com.au; 
>>> rsgb_lf_group@yahoogroups.co.uk
>>>  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 <Stefan.Schaefer@iup.uni-heidelberg.de>
>>>  An: rsgb_lf_group <rsgb_lf_group@blacksheep.org>
>>>  Cc: Edgar J Twining <edgarjtwining@virginbroadband.com.au>
>>>  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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>>>
>>> Links:
>>> ------
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>>>
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>>
>>