Re: LF: slow WSPR?

[Markus Vester <markusvester@aol.com>]

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.. 

>