Hello all,
Note that FT8 vs CW cs SSB bandwidth MDS is a matter of specification.?
Converting from one noise bandwidth to another is a matter of adding 10 log (noise bandwidth ratio).
Similarly for FT8. Here the relevant noise bandwidth is 6.25 Hz (bandwidth of one tone). So you can calculate that for 2500 Hz noise bandwidth, the addition would be 26dB because 10 log (2500 / 6.25) = 26 dB. In other words FT8 has about a 26dB SNR advantage over SSB. All SNR reports in WSJT-X and JS8Call are normalized ro 2500 Hz noise bandwidths.
I would like to confirm that the noise bandwidth in a FSK signal is
referred to a single tone.
From my understanding, If we have 8 tones, to detect the symbol, we
compare 8 magnitudes each other, polluted with 8 sources of noise....
So I was expecting an sensibility improvement of 10*log10(2500/(6.25*8))=17dB
But I never found a clear explanation in textbooks about the topic.
==
A nice idea for these transceivers is to implement coherent CW, as
explained some years ago in QST.
With 6WPM, the BW is as low as 10Hz, and it does not need a computer to operate.
But the lack of interest in these mode against QRSS3..30..60 make me
think twice.
Probably CCW benefits are less than the complexity of sharing a clock
source between TX and RX.
73 dx and happy 25
eduardo ea3ghs
