For practical receiving purposes, a sloping wire, in the midst of
buildings, can be considered to be omi-directional, even isotropic.
Any variations in directivity, in either the vertical or horizontal
planes, although they exist, are not measurable or noticeable. The
random effect of the presence of a nearby building or buildings is
greater than the direction in which the wire may or may not slope.

Sensitivity is frequency dependent. It falls of rapidly when the
length of the antenna is less than 1/6th wavelength at the lowest
frequency of interest.

Of at least as great importance is the grounding system. With ordinary
garden soil you will need at least 5 or 6 shallow buried wires under
the antenna, radiating from a common point in random directions.
Ground wire length need be no longer than 1/12th wavelengths at the
lowest frequency of interest. Lengths and numbers are very
non-critical.

A sloping wire or inverted-L is the best general-purpose antenna you
can get. Just erect something, not forgetting the ground.
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Reg, G4FGQ.