First of all my appologies to those getting bored with my loop inductance
formulas.
But after some 'playing' with simulation software and calcuations it turned
out that there might be a more accurate and simpler formula to calculate
the inductance of a big loop :

L = 0.8*B*(ln(A/d)+6.82)
where L = loop inductance in uH, A = loop height in m, B = loop length in m
and d = wire diamater in mm

At first sight there seems no (practical) limits to the A/B ratio.

If this formula is correct it would also mean that (for a given height) the
loop inductance increase linear with the loop length.

73 from a sunny Belgium (sunny and 22°C ... instead of the rain, wind and
10°C we usually have begin april)

Rik  ON7YD