Roy Lewallen wrote:

David wrote:

Are the electromagnetic field patterns noticeably different according
to whether antenna is receiving or transmitting?

No. They are the same. This is part of what is known as reciprocity.

I think you would agree the field pattern the antenna sees from a
distant source is different than the field pattern the antenna
generates on transmit. The field is uniform about the vertical axis
on transmit and the phase of the signal in each radial is identical.
But on receive the phase of the induced signal is unique into each
radial.

This difference has nothing to do with reciprocity of course, but
noting the differences between a unidirectional field pattern versus
an omnidirectional one might help to clarify the apparent assymetry
between receive and transmit.

73, Jim AC6XG