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Re: [softrock40] uV/m to dBm

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  • Alan
    ... Subject: [softrock40] uV/m to dBm ... Thanks for giving me the relavant information Jack. I did actually find these two sites but my mathematics teacher
    Message 1 of 15 , Mar 15, 2013
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      ----- 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

      > From
      > http://www.softwright.com/faq/engineering/FIELD%20INTENSITY%20UNITS.html
      >
      > 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.,
      > http://www.giangrandi.ch/electronics/anttool/field.html
      >
      > Jack K8ZOA
      >
      >
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