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More work on section 7.
git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@6382 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
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Steven Franke
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lib/ftrsd/ftrsd_paper/fig_subtracted.tiff
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lib/ftrsd/ftrsd_paper/fig_subtracted.tiff
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@ -2239,172 +2239,6 @@ MAP65
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\emph default
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\emph default
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.
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.
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\end_layout
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\begin_layout Standard
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Mention two-pass decoding - could use Fig
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\begin_inset CommandInset ref
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LatexCommand ref
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reference "fig:spectrogram"
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\end_inset
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as a case study.
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The table below is for the data shown in Fig
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\begin_inset CommandInset ref
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LatexCommand ref
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reference "fig:spectrogram"
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\end_inset
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.
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Maybe less confusing if the third row was deleted.
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\begin_inset Float table
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wide false
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sideways false
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status open
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\begin_layout Plain Layout
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\align center
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\begin_inset Tabular
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<lyxtabular version="3" rows="5" columns="2">
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<features rotate="0" tabularvalignment="middle">
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<column alignment="center" valignment="top">
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<column alignment="center" valignment="top">
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<row>
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<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
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\begin_inset Text
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\begin_layout Plain Layout
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Case
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\end_layout
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\end_inset
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</cell>
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<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" rightline="true" usebox="none">
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\begin_inset Text
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\begin_layout Plain Layout
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# decodes
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\end_layout
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\end_inset
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</cell>
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</row>
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<row>
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<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
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\begin_inset Text
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\begin_layout Plain Layout
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one-pass, BM
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\end_layout
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\end_inset
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</cell>
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<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
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\begin_inset Text
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\begin_layout Plain Layout
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9
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\end_layout
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\end_inset
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</cell>
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</row>
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<row>
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<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
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\begin_inset Text
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\begin_layout Plain Layout
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one-pass, FT
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\end_layout
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\end_inset
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</cell>
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<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
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\begin_inset Text
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\begin_layout Plain Layout
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12
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\end_layout
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\end_inset
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</cell>
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</row>
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<row>
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<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
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\begin_inset Text
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\begin_layout Plain Layout
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two-pass, BM
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\end_layout
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\end_inset
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</cell>
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<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
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\begin_inset Text
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\begin_layout Plain Layout
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12
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\end_layout
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\end_inset
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</cell>
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</row>
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<row>
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<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
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\begin_inset Text
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\begin_layout Plain Layout
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two-pass, FT
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\end_layout
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\end_inset
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</cell>
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<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" rightline="true" usebox="none">
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\begin_inset Text
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\begin_layout Plain Layout
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21
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\end_layout
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\end_inset
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</cell>
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</row>
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</lyxtabular>
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\end_inset
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\end_layout
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\begin_layout Plain Layout
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\begin_inset Caption Standard
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\begin_layout Plain Layout
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The effect of soft-symbol decoding combined with signal subtraction on the
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data shown in Figure
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\begin_inset CommandInset ref
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LatexCommand ref
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reference "fig:spectrogram"
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\end_inset
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.
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\end_layout
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\end_inset
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\end_layout
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\begin_layout Plain Layout
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\end_layout
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\end_inset
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\end_layout
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\end_layout
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\begin_layout Subsubsection*
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\begin_layout Subsubsection*
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@ -2437,20 +2271,22 @@ moonbounce
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reflection paths at HF.
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reflection paths at HF.
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Use on HF was not originally an intended application for the mode, but
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Use on HF was not originally an intended application for the mode, but
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at present HF use accounts for the largest number of 2-way contacts.
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at present HF use accounts for the largest number of 2-way contacts.
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Figure
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\end_layout
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\begin_layout Standard
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Figure
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\begin_inset CommandInset ref
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\begin_inset CommandInset ref
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LatexCommand ref
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LatexCommand ref
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reference "fig:spectrogram"
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reference "fig:spectrogram"
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\end_inset
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\end_inset
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is a spectrogram with frequency in Hz on the horizontal axis showing JT65
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(top) shows JT65 activity in a one-minute time-segment on the 20m amateur
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activity during a one-minute time-segment (JT65 transmissions start at
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band during crowded daytime band conditions (JT65 transmissions start at
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the beginning of a minute and last for approximately 47 s).
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the beginning of a minute and last for approximately 47 s).
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The data was collected in the 20m amateur band during daytime under crowded
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band conditions.
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With some straightforward signal processing to demodulate the signals and
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With some straightforward signal processing to demodulate the signals and
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produce soft-symbol data for the FT decoder it is possible to extract and
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produce soft-symbol data for the FT decoder we are able to extract and
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decode 21 messages from the data summarized in Figure 5.
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decode 21 messages from the data summarized in Figure 5.
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This is achieved with a relatively small timeout parameter
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This is achieved with a relatively small timeout parameter
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\begin_inset Formula $T=1000$
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\begin_inset Formula $T=1000$
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@ -2459,9 +2295,23 @@ reference "fig:spectrogram"
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and in spite of the fact that the 200 Hz-wide 65-FSK (sync plut 64-FSK)
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and in spite of the fact that the 200 Hz-wide 65-FSK (sync plut 64-FSK)
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signals overlap, with as many as 4 signals superposed in some parts of
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signals overlap, with as many as 4 signals superposed in some parts of
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the spectrum.
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the spectrum.
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Using exactly the same pre-processing, but without soft-symbol information
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To achieve these results we use two successive sweeps over the spectrum.
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the errors-only BM decoder is able to decode only 12 messages.
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The strongest signals are sequentially decoded and then subtracted from
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the spectrum on the first pass.
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Figure
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\begin_inset CommandInset ref
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LatexCommand ref
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reference "fig:spectrogram"
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\end_inset
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(bottom) shows the spectrogram after subtracting 12 signals that were decoded
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in the first pass.
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Another 9 signals are decoded from the data shown in the bottom figure
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on the second pass.
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Using exactly the same pre-processing, but without soft-symbol information
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the errors-only BM decoder is able to decode only 12 messages in two passes
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over the data.
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\end_layout
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\end_layout
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\begin_layout Standard
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\begin_layout Standard
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@ -2481,6 +2331,18 @@ status open
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\end_inset
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\end_inset
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\end_layout
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\begin_layout Plain Layout
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\begin_inset Graphics
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filename fig_subtracted.tiff
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width 6.5in
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BoundingBox 0bp 0bp 1126bp 202bp
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clip
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\end_inset
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\end_layout
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\end_layout
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\begin_layout Plain Layout
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\begin_layout Plain Layout
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@ -2493,10 +2355,10 @@ name "fig:spectrogram"
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\end_inset
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\end_inset
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A spectrogram showing one minute of data collected under crowded band conditions
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(top) A spectrogram showing one minute of data collected under crowded band
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on 20m during daytime hours.
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conditions on 20m during daytime hours.
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WSJT-X extracted 21 JT65 messages in approximately the same bandwidth required
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(bottom) The spectrogram after the subtracting all signals successfully
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for a single SSB signal.
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decoded on the first pass.
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\end_layout
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\end_layout
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