Whoever authored "AM Loop Antennas" attached to Chuck Olson`s posting
wrote:
"A spiral loop is least sensitive to signals received in its plane."

Nonsense. Spiral, edgewound, or whatever, any loop antenna which is
small in terms of wavelength is sensitive to signals within its plane,
and insensitive to signals broadside to its plane.

My authority is Kraus` 1950 edition of "Antennas", page 160, Fig. 6-6.

The plane wave arriving broadside to the small loop tends to generate
currents in the same direction in all sides of the loop. The sides of a
turn in the loop are connected in series. So, the currents in opposite
sides of the loop tend to add to zero when the wave sweeps the loop from
broadside.Time of arrival and phase are the same on both sides of the
loop from broadside.

Best regards, Richard Harrison, KB5WZI