Reg, G4FGQ wrote:
"All I need is a number of volts."

I`ll guess, because Reg asked, not because I know aanything. I`ve now
discovered Kraus` effective antenna height which may be related to an
Icelandic connection. Reg hasn`t told us everything he knows. One reason
we don`t know is because the effective antenna height is related to the
antenna`s length in terms of wavelength according to Kraus. One of the
examples given by Kraus is a dipole of 1/10 of a wavelength. Kraus tells
us the effective height of this length gives a factor of 0.5. According
to Equation (1) on page 30 of the 3rd edition of "Antennas", Voltage at
the terminals of the antenna = effective height X field strength.

If we guess that a short whip might have the same effective height as a
short dipole, then with a 1 volt per meter field strength X 0.5 as an
effective height factor, their product would be 0.5 volts. I`ll assume
rms because that`s the convention for expression.

I don`t have much confidence in the number because I think you must
determine the effective height experimentally. Terman says on page 991
of his 1943 "Radio Enginneers` Handbook: "If an antenna other than a
loop is used, the effective height must be determined experimentally.
Maybe someone has worked this out since 1943.

Best regards, Richard Harrison, KB5WZI