From HB9ASB, JN36pt
Today I've made some comparisons of different Audio-filter settings and
CW against Slow CW. All test were made blind and under real band-noise
conditions with the main receiving antenna (low noise, no QRN) and a
QRP-TX with a separate antenna. Here the main results (RX Harris RF590):
1. Good audio filters with BW from 10 to 50Hz may give a 6dB advantage
above the receiver without Audio-filter (250Hz IF). A 150Hz passive
LC-filter was somewhere in between.
2. There is no big difference between different BW in the range from 10
to 50Hz. Although I got the impression that 10Hz was already to small
and 20Hz the optimum in my case (Timewave DSP599zx)
3. Slow CW with the Spectrogram (3sec dots) gives an advantage of about
10dB above aural CW with narrow audio filtering.
4. I can confirm the optimal settings of Spectrogram found by Marco,
IK1ODO
5. There is no clear advantage of using longer dot-periods (e.g. 10s).
These findings differ from theoretical values but it proves how good our
ear-brain detector works.
73 de Toni
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