On Sat, Oct 10, 1998 at 06:45:03AM -0700, William Sommerwerck wrote:
> The same principle is used in radio antennas, particularly for FM
> stations. If a station's antenna is horizontal, the vertical antennas on
> automobiles don't do a very good job of picking up the signal (and
> drive-time ad revenue is critical for keeping many stations on the air).
> So, by using two antennas that are one 1/4-wave out-of-phase *, you
> generate a circular wavefront that has both vertical and horizontal
> components, and can be picked up regardless of the receiving antenna's
> orientation.
There's one effect in radio antennas that may or may not apply here: A
circularly polarized signal, when received on a linearly polarized antenna,
is half as strong as a linearly polarized signal with the same radiated
power in the same plane. (This compares with a linearly polarized antenna at
90 degrees to the orientation of the transmit antenna, which is only 1/1000
as strong.) Clearly, this is a win for the radio station, which can simply
use a higher-gain antenna or increase its transmit power to compensate.
Does a circularly polarized light wave suffer the same loss when passing
through a linear polarizer, such as, say, the OM-PC's metering system? Does
it simply compensate for the 1-stop loss, or does it need to, or...?
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