Roy Lewallen wrote in message ...

In the far field, the field strength E from any antenna is sqrt(PD *
Z0), where Z0 is the impedance of free space, very nearly 120 * pi ohms.
E is in volts/meter if PD is watts/meter^2 and Z0 is in ohms.


Oh, i think it's something like this:

Power density is in Watts per square meter, or V**2/(R*m**2).
If you accept that R = impedance of free space = Z0, then these will
cancel, and you are left with E = sqrt (V**2/m**2) = V/m.


Slick