Re: [softrock40] uV/m to dBm
----- Original Message -----
Subject: [softrock40] uV/m to dBm
> There's a frequency factor that must be included when converting between
> field strength in uV/m and signal power.
Thanks for giving me the relavant information Jack.
I did actually find these two sites but my mathematics teacher never told me all those formulae could be useful and interesting so I
tend to run a mile when I see them! So I missed the frequency related factor.
Now I make sense of the calculator.
73 Alan G4ZFQ
> E(dBµV) = E(dBµV/meter) + Gr(dBi) - 20log f(MHz) + 29.8
> P(dBm) = E (dBµV) - 107
> P(dBm) = E(dBµV/m) + Gr(dBi) - 20log F(MHz) - 77.2
> where P(dBm) is received power into 50 ohms, in dBm
> E is the received signal voltage in dBuV
> Gr is the receiving antenna gain in dB with respect to isotropic
> f is frequency in MHz
> E is the field intensity in dBuV/meter
> At 28 MHz, the -20 log f(MHz) almost exactly cancels the +29.8 so the
> received signal voltage equals the field strength plus antenna gain. But
> that's not the case generally.
> On-line calculators relating these factors can be found at many places
> on the Internet, e.g.,
> Jack K8ZOA