I thought that the ghost signals were indeed caused by hum or other badly adjusted transmitters until I noticed that I also saw them on stations that I know have a high level of technical competence and when people reported them on me. I always monitor my transmissions and these artefacts are not present on my transmissions. I take great care not to radiate a poor signal as do the aforementioned stations. There is a mixture of poor quality signals and genuine ghost signals which Joe has convinced me must be due to AP scatter. As I said before I was surprised not to see any doppler slope on the signals but Joe has now explained this.
The fact is that we just have to live with them. Of course when you see transmissions which have ghosts 20dB down which are harmonically related to local mains frequencies then a quiet friendly word with those stations is a good idea. 73 Conrad PA5Y From: Reino Talarmo <reino.tala...@kolumbus.fi> Sent: 14 July 2019 06:32 To: 'WSJT software development' <wsjt-devel@lists.sourceforge.net> Subject: [wsjt-devel] signal report RST Hi All, There has been many situation, where FT8 signal quality is less than perfect due to hum, actually hum related harmonics. In one example hum related sidebands were down relative to the intended signal: Delta frequency, signal strength -600 = 10 x 60 Hz, -41 dB -240 = 4 x 60 Hz, -29 dB -120 = 2 x 60 Hz, -24 dB In some contest we use RST reports assuming that readability is 5, which is valid as long as signal is decoded; operator could give a lower value based on waterfall, but that’s not reliable). Signal strength value is based on the S/N value, which is a good way to report signal strength instead of 599 as used in many CW contests. The signal tone is assumed always to be perfect and is reported as 9. The above shows how in real life situation unfortunately is not always so good. In the CW Tone quality values are defined a bit differently in various sources, but this list gives the idea: T (cw only) 1 Sixty cycle a.c or less, very rough and broad 2 Very rough a.c., very harsh and broad 3 Rough a.c. tone, rectified but not filtered 4 Rough note, some trace of filtering 5 Filtered rectified a.c. but strongly ripple-modulated 6 Filtered tone, definite trace of ripple modulation 7 Near pure tone, trace of ripple modulation 8 Near perfect tone, slight trace of modulation 9 Perfect tone, no trace of ripple or modulation of any kind The above example could fall in somewhere between 5 to 8, perhaps close to 6. I know that that we can live without an actual Tone value reporting, but sometimes those hum related sidebands do prevent decoding of other signals and it would be nice to have a way to report it to the sender in contests. Perhaps Tone report selection in contest mode could be added into the list on least important nice features. (Of course somebody could send me a free text such as ‘OH3MA RST 597’ or ‘OH3MA TONE 7’ or ‘OH3MA T 7’) 73, Reino oh3ma
_______________________________________________ wsjt-devel mailing list wsjt-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/wsjt-devel
