--- On Mon, 5/4/09, k...@comcast.net <k...@comcast.net> wrote:
> From: k...@comcast.net <k...@comcast.net>
> Subject: Re: [Elecraft] K3 on-channel strong signal overload?
> To: elecraft@mailman.qth.net
> Date: Monday, May 4, 2009, 3:10 PM
> Good day:
>
> I can't help myself. :-)
>
> The "usual" definition of an S9 signal is 50
> uVolts, or -73 dBm (assuming a
> 50 Ohm load).
>
> The "S-Meter" unit is a 6 dB change in VOLTAGE,
> not power. To get one VOLT,
> we need 2000 times 50 uVolts, or S9 + about 86dB (86 dB
> over S9).
>
> 40 over is about 5 mVolts...
>
> The formula for the dB difference for two voltages,
> assuming you want a power
> and have the same load, is
>
> 20 * log (V2/V1). If you want dB's "over"
> S9, let V1 be 50 uV, (50E-6 Volts).
>
> Now, let's hope I managed to get this right. :-)
You got the right answer (86 dB) but when using your slide rule you didn't keep
track of the decimal point. One volt is 20,000 * 50 uV.
Wes Stewart, N7WS
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