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Re: [softrock40] Power and Signal Levels

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  • Bill Dumke
    BTW, the decibels difference between the two signals should be 20*log(50uV/1uV) or 10*log(2500/1) both of which are 34 dB, not 17dB. Bill wa9pwr
    Message 1 of 8 , Apr 29, 2007
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      BTW, the decibels difference between the two signals should be
      20*log(50uV/1uV) or 10*log(2500/1) both of which are 34 dB, not 17dB.

      Bill wa9pwr

      Kees & Sandy wrote:
      >
      > Interesting ....I've always connected a pad or termination across my
      > signal generators (URM-25 or HP-8640) to get the levels correct
      > relative to the meters since most are designed and set up for a 50ohm
      > load. I assumed the XG-1 or XG-2 would be the same. I think we need
      > some more input.
      >
      > 73 Kees K5BCQ
      >
      >
      > -- Bill Dumke <billd@...> wrote:
      > No pad. Direct connection. The XG1 was used to calibrate Rocky 3.2's
      > S-meter.
      >
      > Bill wa9pwr
      >
      > Kees & Sandy wrote:
      > >
      > > Is that with a 50 ohm pad in there somewhere ?
      > >
      > > 73 Kees K5BCQ
      > >
      > >
      > >
      > > -- Bill Dumke <billd@...> wrote:
      > > Kees,
      > >
      > > I get 26 dB difference here using my XG1 and Rocky 3.2. It goes from
      > > -68 dB to -42 dB from 1 uV to 50 uV.
      > >
      > > Bill wa9pwr
      > >
      > > Kees & Sandy wrote:
      > > >
      > > > I thought I knew this ....but, so I'll ask.
      > > >
      > > > S-meter readings are really a measurement of the power in the passband
      > > > where the AGC and S-meter circuits are and assume a properly
      > > > terminated antenna input, usually 50 ohms. The "standard" is S9 which
      > > > equates to 50uV at th e 50 ohm impedance antenna terminals and can also
      > > > be stated as -73dBm from a voltage standpoint. A 1uV signal can be
      > > > equated to -107dBm and is 34dB less voltage&nbs p
      > ;but 17dB less power. So on
      > > > Rocky (or any others) I should see a 17dB difference between a 50uV
      > > > signal and 1uV signal at the antenna terminals. Right ?
      > > >
      > > > 73 Kees K5BCQ
      > > >
      > > >
      > > >
      > > >
      > > >
      > >
      > >
      > >
      > >
      > > Yahoo! Groups Links
      > >
      > >
      > >
      > >
      > >
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      > Yahoo! Groups Links
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