> VERY important distinction -- what do you mean by "in phase" and "out
> of phase?" Phase is a continuous function having an infinite number of
> values, and is proportional to frequency.
Unless every receiver oscillator is common to each other you can accomplish
the same thing as shifting polarity OR phase by slightly tuning the dial of
the receivers or any oscillator in the receiver. If the oscillators are not
forced to lock with each other or common oscillators in a fraction of a
second they will be out of phase (and "polarity") in a few seconds.
You can hear this on sound files at:
http://www.w8ji.com/polarization_and_diversity.htm
Phasing the receiver audio output is absolutely no different that phasing
two antennas, and flipping one speaker lead is no different than flipping an
antenna phase 180 degrees. I can totally null the audio of something like
W1AW for example, even though the signals are 30 over nine. You CANNOT do
that if even one oscillator is not locked or common to both receiver chains.
While there is some difference between hearing the same basic signal sound
in each ear (stereo) when the receivers are not locked, the difference in
copying weak signals in or near the noise is substantially better only when
the receivers are exactly locked. If the receivers are locked with similar
phase errors in filters, the effects are substantially improved.
The antennas also have to have similar good S/N ratios or dual use won't
work. You can't combine a noisy channel with a clean channel and improve
results, it actually makes copy worse. It isn't any different mixing at
audio than mixing at the antenna, and your brain has a difficult time
correcting phase (it can do that in stereo) when the phase is more than a
small fraction of a Hz off.
73 Tom
_______________________________________________
Topband mailing list
Topband@contesting.com
http://lists.contesting.com/mailman/listinfo/topband
|