Roy, W7EL wrote:
"The calculations you qupte assume equal and opposite (i.e. purely
differential mode) currents in the feedline conductors. The topic under
discussion is radiation due to common mode current."

Radiation from current on the outside of a coax feedline can be
calculated too by using formulas appropriate to the actual current
distribution.

Refer to the infamous "ARRL Antenna Book" figure (Fig 24 on page 26-16
of my 19th edition), "showing various current paths at feed point of a
balanced dipole fed eith unbalanced coaxial cable."

From the text:

"The antenna current in arm 2 is thus equal to the difference between I2
and I3.

The magnitude of I3 (on coax exterior) is proportional to the relative
impedance in each current path beyond the split."

Best regards, Richard Harrison, KB5WZI