Rik Strobbe wrote:

Saturday afternoon I was in the shack and had ARGO running (at 3sec/dot)
while being otherwise occupied. at 17.50 I saw a very faint interruped line
on 137701, 'T' copy at best. It seemed 10sec/dot QRSS to me, so I switched
ARGO to 10sec/dot and the faint line became a 'O' copy signal of what
seemed the end of a QSO as I could just copy : 'TNX E E SK'.
Conclusion : 10 sec/dot can make a real difference over 3 sec/dot (from 'T'
to 'O')
Question : who's transmission did I catch ?

73, Rik  ON7YD

At 10s dot the FFT bin size is exactly 1/4 of the size at 3s dot. So, if the 
noise power
is evenly distributed, and the wanted signal falls exactly in a single bin, 
there is a 6 dB
S/N improvement from passing from one mode to the other. How those 6 dB 
translate
into a visual gain is difficult to say, given also the higly non-linear mapping 
between
magnitudes and color saturation in Argo.

73   Alberto   I2PHD