--- Bill Tippett <btippett@alum.mit.edu> wrote:
> K3BU wrote:
> >That reminds me the "noise floor" thing in Orion.
Disconnecting or shorting the antenna terminals on
Orion produced quite a bit of "noise floor." This
appears to be a noise generated by the circuits (IF
amp after mixer?) Turning the preamp on, increases the
noise slightly, without moving Smeter.
>
> It depends on what Threshold is set to of
course. Using a 50 ohm load directly on the antenna
terminal, 350 Hz BW, AGC off and preamp on, it does
sound noisy at my normal AF setting.
Isn't it possible that what's really happening here is
that the DSP is interpreting the absence of signal as
very weak signal and applying very high gain in order
to optimize the signal applied to the input of the
ADC? The net result is it sounds noisy but it really
isn't. I think it might have been Grant who posted
some info a coupla months back that did a great job of
theorizing what is happening here.
73,
Barry N1EU
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