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Mal,
Main cause of decode fail with Opera is s/n , ie in
qsb if more than 50% of the signal is lost, as in
the s/n has dropped below the detector threshold ,
caused by signal fading or local
'noise' source being activated , then that cycle will
fail, lowering the threshold , results in a increase of
'false decodes'
Noise bursts are not a problem as the duration is
very short compared to the 'tx pulse length' , and where 'time
hopping spread spectrum' is used FEC , then noise
burst's are not a problem..in Operas case, the
data encoding provides this function , as the
losses can be randomly or block distributed along the
time line
Yes a trace on SL is the most simple method,
but as you note, and will catch the lifts
in signal during the time period
But as yet , this has not produced a
full call sign down under , or reliably
across the pond , ok there are data modes
that will layer / multi pass , psk gives another 6
db , but these all require linear systems and at
these power levels, that not practical
73 -G..
Sent: Sunday, July 15, 2012 8:13 AM
Subject: LF: DX
Reference recent discussion about Opera
es Wspr for long haul DX.
Although these modes have some merit they would be more
vunerable over long distances to QSB and long bursts of QRN and therefore a
decode would be difficult.
QRSS es DFCW would be more suitable because part of the
callsign/information would be readable at some time during the transmission.
I have noticed this on local data transmissions on
500 Khz, no decodes because of QSB or QRN bursts but I can clearly see the trace
and had it been QRSS or DFCW I could easily have had an ID or parts of
the information.
ie
With data modes a DECODE or nothing, with QRSS/DFCW at
least some information.
de mal/g3kev
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