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: [email protected]
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
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From: "Mike Dennison" <[email protected]>
Sent: Saturday, January 10, 2015 11:09 AM
To: <[email protected]>; <[email protected]>
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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