[hpsdr] High S meter reading on noise floor.

[Warren C. Pratt]

Hi Ari,

"Sig Avg" is the correct S-meter setting to read noise.  "Signal" gives 
you a peak reading (appropriate for signals) while "Sig Avg" gives you 
an average reading.

The S-meter reads the noise power within the width of the bandpass 
filter, 1.5Khz in your example.  The panadapter shows the noise power 
within each frequency "bin".  The width (bandwidth) of the bin is 
displayed on the Setup/Display/RXx tabs.  To correctly read noise on the 
panadapter, you should choose the "Average" detector and either "None" 
or "Recursive" as your averaging mode. If the "1Hz BW" box is checked, 
the result displayed on the panadapter will be normalized to a 1 Hz 
bandwidth.  The noise readings of the S-meter and the panadapter are 
therefore related by the equation:

S_reading = Panadapter_reading + 10*log10 (bandpass_width / 
panadapter_bin_width)

I realize all that is a bit complicated.  However, if you master the 
various settings, your SDR is an excellent spectrum analyzer for 
accurately measuring both signals and noise.

73,

Warren  NR0V

> Hi
>
> On 6 meter I have noise floor  -132 dBm      same time Smeter say -114 dBm
>
> and S meter say 5.1 bandwidth is 1.5k
>
> RX1 Meter is set to Sig Avg, I get higher reading with Signal.
>
> Why do S meter not say same reading as Panadapter ?
>
> And how can I have S meter 5  With only noise of -132 dBm ?
>
> And where do Smeter get -113 dBm ?
>
> And why do we have 24 hours in day 😊
>
> Ari  TF3ARI
>
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