To All from PA0SE
Aldo, IZ1ANT, wrote:
Dear Alan,
if I understand well,you are receiving CW by ear, not by
Spectrogram.
For receiving CW by ears I found very useful a stereo processor,
like that described in
http://hem2.passagen.se/sm0vpo/use/stereo.htm
which allow to "spatially" spread signals (and noise) " in front of
you":
lower frequency signals are stronger in the left earphone
speaker, and higher frequency in the right one. In this way you can
simply concentrate your brain in the signal coming from a certain
"virtual direction"
It's interesting with large filters (e.g. 500 Hz), however I never
tryied it with narrower filters. It may need some adjustment...
73 Aldo IZ1ANT
I have made such a gadget myself with a "centre frequency" of 900 Hz.
It indeed produces a surround effect effect which at first sounds very
surprising and promising.
But careful and repeated evaluation showed it contributed absolutely
nothing to the readibility of a weak signal in noise. Wide or narrow band
filtering preceding the pseudo-stereo unit made no difference.
I get the best result with my home made passive 35 Hz wide audio bandpass
filter (four tuned circuits with coils in pot cores) between the output of
the receiver and the headphones. It is a phase-linear design and therefore
does not ring.
Speeds up to 24 WPM are passed by the filter, but before that my ear/brain
system starts ringing....
Butterworth, Chebychev and Cauer (elliptic) filters are not phase-linear and
do do ring, though they have a steeper transition between pass- and
stopbands.
73, Dick, PA0SE
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