Jimmie D wrote:

Normally WWV rxceivers have there antennas tilted at 45 degrees in an
attempt at polarity diversity. Im not sure if the department store clocks do
anything like this. The only one I have ever seen used a loopstic antenna.
The professional grade rx I am familar with that was used to set the time on
a computer used a contuously loaded dipole on an outside mount with 45
degree polarization.

*Chuckle*

Tilting would work fine if an incoming wave couldn't have any
polarization except vertical or horizontal. But it can -- it can be at
any angle. So it doesn't matter how you tilt the antenna, the
probability of the incoming wave's polarization being aligned with it,
at right angles to it, or having any other relationship to it, is the
same as for any other tilt. (For simplicity, I'm ignoring the fact that
the probability of a wave arriving with a particular polarization angle
varies with the elevation angle when ground reflection is involved --
which it virtually always is with HF skip propagation.)

A 45 degree tilt might be useful if you were receiving a line-of-sight
signal which might come from either a horizontally or vertically
polarized antenna. But even then, if the transmitter's antenna was
tilted 45 degrees the other way, you'd be cross polarized and in the
same boat as if one were horizontal and the other vertical.

One solution is a circularly polarized antenna, which responds equally
well to linearly polarized waves at any polarization angle. However,
there are a few problems involved with that. First, it's difficult to
get circular polarization from an antenna when ground reflections are
involved. Second, most of the simpler circularly polarized antennas like
a turnstile are circularly polarized in only one or two directions. For
that antenna, for example, the polarization is elliptical at other
azimuths and elevation angles, and linear to the side. And finally, it
seems to me possible that ionospheric propagation can cause a received
signal to be elliptically polarized even though it's linear when it's
transmitted. I don't know if this is the case, but if it is, it
guarantees that even a circularly polarized antenna would experience
fading from polarization shift. Of course, even if you completely
eliminate fading from polarization shift, you still have to deal with
multipath.

Roy Lewallen, W7EL