[R-390] R390a and SDR

[Alan Victor]

Hello again.

I did not imply that the R390A was limited to -100 dbm at its INPUT. I
indicated that its noise power at its output might be as high as -100 dBm.
Most likely higher, Lets consider the sensitivity equation. Its pretty
straight forward.

Sens (dBm) = -174 + 10 log (BW) + NF (dB) + S+N/N ratio in dB for desired
intelligibility.

Lets plug in some typical numbers. BW: 3 kHz, NF: 10 dB, S+N/N: 10 dB

Then SENS is -174+30+10+10 = -124 dBm. Obviously if we reduce the BW by
another order of magnitude then we could achieve -134 dBm and so on. The
noise power OUT would be dictated by the input sensitivity or the NF
multiplied by the total forward gain of the receiver. Additional gain could
be added as required as long as we don't compromise distortion, IMD, etc...
Alan

On Mon, Apr 22, 2019 at 3:45 PM jm <josemic at gmail.com> wrote:

> John
>
> Very clear and educational.
>
> Many thanks
>
> Jose
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