[Elecraft] copying CW QRQ

[Jim Brown]

On Tue, 24 Feb 2004 07:43:37 -0700, Indy wrote:

>Cw becomes difficult to copy at high speeds because of the Haas Effect. 

As a consultant in audio and acoustics, I consider this reference to
the so-called "Haas Effect" to be a completely incorrect reference to
this powerful characteristic human hearing. Haas, and many others who
studied human hearing long before Haas, learned that when humans hear a
sound coming at them at multiple times and from multiple directions,
the brain will assign direction to the sound that arrives first. They
also learned that speech intelligibility will be degraded if the later
arriving sound is delayed more than about 30 msec, but humans won't
consciously be aware of the echo until the delayed arrival is longer
than about 80 msec. 

Note that the above has NOTHING to do with the rise time of keying. It
DOES, however, apply to an effect I've heard on HF when my relativley
low directivity antenna hears a DX signal arriving from more than one
transmission path, and thus at different times. The signal with the
longer path is heard as an echo, and degrades intelligibility both of
speech and CW. Under such conditions, I've had trouble copying CW. 
During a contest a few months ago, the condition was so severe on 20
meters that I had to QSY to 15 meters. 

 BTW, the perception of echoes was discovered and documented a full
century before Haas (1949) by Joseph Henry (1849), the American
scientist who was honored by putting his name on the unit of
inductance, and who is far better known for his invention of motors and
voltmeters. Haas is better known because his very good paper on the
topic was published in more modern times, and when folks were more able
to understand the concepts and realize their importance. 

Jim Brown K9YC