Soliloquy . ..

^ How about radiation patterns.

^ Is there an analogy to radiation patterns for reception (onmi-
^ directional antennas, still, as someone has suggested, perhaps
^ a degree of directionality) and could this be a factor?

I know that a Yagi is similarly directional for both transmit and receive so
it may be true for most antenna configurations.

You can make a very simple directional antenna by placing an element that is
slightly longer than your antenna's radiating element about one-eighth
wavelength from the antenna:

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The diagram isn't to scale -- the longer element should only be a few percent
longer. The shorter element is the antenna. In the diagram above, the main
lobe (the best reception) would be to the right. The longer element is a
reflector and tends to block signals from the left while enhancing signals
from the right.

If the additional element were a few percent shorter then it would enhance
the signal from the same side. This additional and shorter element is a
director.

If you place your antenna near other metal objects then a similar effect
might occur.

If you use both a reflector and a director

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each one-eighth wavelength from the antenna in the center, then you have a
Yagi. The antenna in the center should be a have-wave dipole. You could add
additional reflectors to the right, each a little shorter than the previous,
at one-fourth wavelength intervals:


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The spacing between elements is as stated but the antenna can be enhanced by
using precise measurements for the elements (reflector, antenna, and
directors) that consider the wavelength and the velocity factor of the
conducting material. But anything close will have some effect.

Frank