On 09/03/2013 06:37 PM, Hans Hammarquist wrote:
> Even vertical antennas, mounted one above the other and fed out-of-phase
> still have directions with constructive interference, that is directions with
> radiation.
>
>
> Bob's demonstration with out-of-phase speakers sounds awful as we are
> watching a wide-band signal, speech unlike the RF signals from a radio
> transmitter that is almost monochrome. The same reason you see all these
> beautiful patterns from a LASER beam.
There is another reason. Sound frequencies are really low, so speakers
that are run out of phase (and in the same room) are close to zero
wavelengths apart, and can actually cancel out the bulk of each other's
signal.
Stacked antennas tend to be 1/4 or more wavelengths apart, so running
them in phase, or out of phase, simply results in different radiation
patterns. They are too far apart to completely cancel out each other's
signals.
--
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