On Thu, 27 Jan 2005 08:11:34 -0800, "Caveat Lector"
wrote:

Also for weak signal detection, listening with headphones can make a big
difference in comprehension as compared to listening to a speaker. Using the
above techniques and head phones, top notch CW operators can copy code even
when the signal is about the same as the noise.

I can't do this though (;-(
old ears I guess (;-)

Hi OM,

Well, back when I was in college physics (before the flood), my
professor put me and a buddy on a task to build the perfect detector.
It correlates perfectly with your advice to use headphones.

He had us build a Synchronous Detector (not a simple device to
construct from tubes and at 455 KHz). Some may be familiar with this
form of detection, and yet they may be ignorant of its best
implementation. For others, this kind of detector is also found in
color TV detection and color information separation. Often the block
diagramming or circuitry is described in terms of I and Q paths. I
won't go into the particulars of design, but I will offer that these
two separate paths when broken out to separate Audio channels, and
then fed to stereo head phones, they offer an unique signal hearing
experience.

Basically, the entire two channel system is completed by the brain
combining phases and providing a perception of the wanted signal being
"heard" in the middle of your skull, while interfering off-frequency
signals are perceive off to one side or the other. In a sense, you
hear an enhanced signal through phase reinforcement.

73's
Richard Clark, KB7QHC