From 5a3e9842c426422b77ce65b3fe7e9981b6ca34c7 Mon Sep 17 00:00:00 2001 From: Steven Franke Date: Sun, 10 Jan 2016 00:42:26 +0000 Subject: [PATCH] Some tentative ideas for section 8. OK to change, delete, etc. git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@6377 ab8295b8-cf94-4d9e-aec4-7959e3be5d79 --- lib/ftrsd/ftrsd_paper/ftrsd.lyx | 42 +++++++++++++++++++++++++++++---- 1 file changed, 37 insertions(+), 5 deletions(-) diff --git a/lib/ftrsd/ftrsd_paper/ftrsd.lyx b/lib/ftrsd/ftrsd_paper/ftrsd.lyx index fe2008de7..1011a986e 100644 --- a/lib/ftrsd/ftrsd_paper/ftrsd.lyx +++ b/lib/ftrsd/ftrsd_paper/ftrsd.lyx @@ -2245,14 +2245,46 @@ MAP65 Mention two-pass decoding. \end_layout -\begin_layout Standard -Experience with FT on crowded HF bands. - +\begin_layout Subsubsection* +Experience with FT on crowded HF bands: \end_layout \begin_layout Standard -Re Figure 5 - just playing around with ideas. - May not be appropriate for this paper. +(Re the following paragraph and Figure 5 - just playing around with ideas + - feel free to change, delete, etc.) +\end_layout + +\begin_layout Standard +The JT65 mode has proven to be remarkably versatile. + Thousands of users regularly use the mode for two-way communication over + straight line-of-sight paths and the earth-moon-earth ( +\begin_inset Quotes eld +\end_inset + +moonbounce +\begin_inset Quotes erd +\end_inset + +) path at frequencies from VHF to microwaves, and over multi-hop ionospheric + reflection paths at HF. + Use on HF was not originally an intended application for the mode, but + at present HF use accounts for the largest number of 2-way contacts. + Figure 5 is a spectrogram with frequency in Hz on the horizontal axis showing + JT65 activity during a one-minute time-segment (JT65 transmissions start + at the beginning of a minute and last for approximately 47 s). + The data was collected in the 20m amateur band during daytime under crowded + band conditions. + With some straightforward signal processing to demodulate the signals and + produce soft-symbol data for the FT decoder it is possible to extract and + decode 21 messages from the data summarized in Figure 5, and this is achieved + with a relatively small timeout parameter +\begin_inset Formula $T=1000$ +\end_inset + +. + Using exactly the same pre-processing, but without soft-symbol information + the errors-only BM decoder is able to decode only 12 messages. + \end_layout \begin_layout Standard