Message-ID: <B17112AF2F5E4E3C8CEB5BF6D383CC13@mePC>
From: "SV8CS-Spiros Chimarios" <zante@otenet.gr>
To: <rsgb_lf_group@blacksheep.org>
References: <54B10878.10172.535233@mike.dennison.ntlworld.com>, <6F0B87EF8D1F4AA0AF70320B15F3E120@AGB> <54B1635A.16750.1B653F9@mike.dennison.ntlworld.com>
In-Reply-To: <54B1635A.16750.1B653F9@mike.dennison.ntlworld.com>
Date: Sat, 10 Jan 2015 17:45:22 -0000
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Subject: LF: SV8CS Opera improving
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Status: O

Another false decode

17:18    136 JA8SCD de SV8CS Op32 Deep Search ?? 9711 km -43 dB in Zakynthos 
Island with 0.001w + dummy

73, Spiros/SV8CS


-----Αρχικό μήνυμα----- 
From: Mike Dennison
Sent: Saturday, January 10, 2015 5:37 PM
To: rsgb_lf_group@blacksheep.org
Subject: Re: LF: Opera improving

The new checking system has just worked. JA8SCD was reported by SV8CS
at nearly 10,000km on 136kHz whilst the JA was using a dummy load.
This is plainly a false decode, but the new software showed "Deep
Search ??" to indicate this should be viewed with caution.

Mike, G3XDV
===========

> Power gain is  close  to  6  dB  , so  that's  a  times  four  over
> the standard   Opera  data  decode limits
>
> Any  numerically  processed  data   mode  is  based  solely on  Guess
> work, just that  Guess   work  is   translated  by  decision  making
> and   fuzzy logic in to a  reproduction  of the  original  message
>
> Modes like  opera / ros / olivia  etc  use  algorithms  to  compress
> and extract the  call , hence  opera  data  miss  decodes, 'have'   a
> normal call  profile  , but  are  not  valid . simple   rtty  just
> produce's  near random  data
>
> In the  case  of  Marcus's  opds ,  your  are  presented  with  a set
> of values ,  a little  deeper ,  these  will  of  been  constructed
> from  a layer  of  fuzzy logic , as  are  the  dsp  decisions  in
> opera  etc ,  in the  case  of Opera dynamic ,  the  outputs  from
> the  data  decoder   and the  'search'  detector  are  assimilated by
> a another  layer  of  decision making  logic
>
> The  command  structure ,  then  decides  at what point  the  decoder
> has failed  and  the  results  from the  detector  are  evaluated ,
> the dynamic call  lists  are  maintained , via tx  web  beacon  and
> 1+1  quality check of  decoded  calls
>
> Table  is  held  for  8 days  We did  have  3 days  as  the  original
> cycle time ,  however ,  as   activity on  136/477  tends  to  follow
> the  7 day week  pattern  , stations  using  pic/pi/U3  and  other  Tx
>  systems ,  with no  web-beacon  would  need  to  be decoded  by  2
> stations  using op32/op8  on there  first  pass, to  catch  the
> second
>
> The show go's on ;)
>
> 73-Graham
> G0NBD
>
>
>
>
>
> --------------------------------------------------
> From: "Mike Dennison" <mike.dennison@ntlworld.com>
> Sent: Saturday, January 10, 2015 11:09 AM
> To: <rsgb_lf_group@blacksheep.org>; <rsgb_lf_group@yahoogroups.co.uk>
> Subject: LF: Opera improving
>
> > There is a British saying "Don't throw the baby out with the
> > bathwater". Amongst the criticism of false decodes (which I have
> > been part of), we must not forget that Opera is now more sensitive -
> > the equivalent of doubling everybody's power - which must be good.
> > This has led to many more good DX decodes.
> >
> > Now, in response to suggestions from users, the writers have
> > modified the program to flag up decodes that might be suspicious,
> > which is what OPDS does (but in a different way). Used with caution,
> > this will address most of the problems experienced with the launch
> > version.
> >
> > The controversial PDF file has also been dropped from the zip file.
> >
> > Deep Search, originally developed by DF6NM, has always involved
> > "guesswork", and therefore needs to be viewed with caution. In short
> > it compares a list of known active stations (again Op and OPDS does
> > this differently) with what might be described as 'partial decodes'
> > and finds the best match. Anyone who has worked DX, operated in a
> > contest or used QRSS will be familiar with that technique. Indeed
> > that is how the human brain works all of the time - it matches what
> > its sees with a huge look-up table of past experiences, which is why
> > we see faces in clouds (a false decode). The key is to use our
> > experience to work out what is true and what is false.
> >
> > I would suggest three more improvements:
> >
> > My understanding is that callsigns in the 'look-up table' are
> > dropped after 8 hours. Reducing this period might help.
> >
> > For those who don't like Deep Search, there should be an 'off'
> > switch, perhaps in the existing Deep Search menu. The 'on' swtch
> > might come with a "use with caution" message.
> >
> > Used carefully, the new v1.5.6 should be a great improvement on the
> > (pre Deep Search) version 1.5.4.
> >
> > Mike, G3XDV
> > ===========
> >
>
>
>
> -----
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