Hello Gang,
Hi Toni,
"Toni Brtschi" wrote:
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):
Very interesting experiments! I do not understand "blind" in
*this* case?
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)
Our ear-brain system is able to decode better if a small amount
of noise is present, probably since it's working at the edge to
quantum mechanics with specific selfmade "noises" (the
pathologic case is known as "Tinnitus aurium"). There are some
scientific articles dealing with hearing CW in noise. One of the
better ones will be found there:
http://www.nitehawk.com/rasmit/br_cpy.html. Furthermore Peter,
SM7CMY got his MD about this stuff; I have a copy.
3. [...]
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).
I cannot confirm this. But I have to fight against pulsatile and
Lux-Effect noise and I'm not using Spectrogram. 3 sec. dot
length often is too short here.
These findings differ from theoretical values but it proves how good our
ear-brain detector works.
They differ from practical experiences working under *different*
conditions.
54°16'N / 10°04'E, JO54ag
73 es gl de Peter, DF3LP
| 