Re: LF: Field strength calcs.

["Dick Rollema" <d.w.rollema@freeler.nl>]

To All from PA0SE

Jim, M0BMU wrote:


> The voltage induced in a loop
> is:
>
> V = 2.1x10^-8 (fNAE)
>
> where f = frequency (Hz)
>         N = number of turns
>         A = area (m^2)
>         E = field strength
> (V/m)
>
> Always assuming that the antennas are far enough apart for the loop to be
> in the "far field" (>1 - 2km seems to be enough)

I think 2km is not quite enough at 73kHz. I calculated the total field
over perfect ground at 2km distance by means of a antenna simulation
program. I found E/H = 342 ohm. In the far field E/H ought to be 377
ohm  (= 120.pi ohm).  So apparently at 2km the near field is
not yet small enough to be negligible.  

I found that even at 137kHz measurements were inconsistent at 2km so I
changed to over 4km.  

73, Dick,  PA0SE