On 28 Dec 2005 10:53:34 -0800, "Ron J" wrote:

Hey all,

I'm still skeptical about this formula:

Field Strength (uV/m) = 10 ^ ( (107 - |dBm| ) / 20 )

Is this valid? I saw this formula somewhere and jotted it down.

Hi Ron,

To answer your question - No.

For one its units do not balance. It is not finding µV/m it is simply
and incorrectly converting to µV. There is no meters to be found on
the right hand side of the equation. The 107, as has been pointed
out, is simply the number of dB below 1mW to a 1µV signal across 50
Ohms. Even here the formula is in error as the sign would be wrong
(the dBm must be presumptively loss expressed as a positive number).
To complicate it further is the artificially forced absolute value
which invalidates any Field Strength (sic) greater than one milliwatt.

You were right to be skeptical, it is nonsense.

73's
Richard Clark, KB7QHC