[Elecraft] P-3 background noise level interpretation

[Alan Bloom]

The effective bandwidth of the P3 is one pixel on the display.
(Somewhat more than that for spans < 5 kHz.)  Each pixel is about 1/450
of the span.

> +/- 10 KHz span: P3 resolution = 20,000/450 = 44.4 Hz
> 
> K3 bandwidth = 2700 Hz (stock filter)
> 
> 10*log(2700/44.4) = 17.8 dB

You got it right.  Assuming 6 dB per S-unit, about an 18 dB difference.

That's only for noise.  CW signals should show the same level on the P3
as on the K3.

Alan N1AL


On Fri, 2010-11-12 at 11:04 -0800, Mike Scott wrote:
> I wonder if someone would check my understanding of interpreting broadband
> noise on the P-3 display.
> 
>  
> 
> I have gone through the P-3 calibration procedure on 40M as well as
> calibrating my S-Meter on the same band. 
> 
>  
> 
> Now when looking at band noise I see the tops of the yellow line at around
> the -110 dBm level. If I run peak-hold, the peaks are maybe -108 dBm in the
> region where the K3 is tuned (between the MKR A cursor). Without further
> interpretation this would indicate S-3 or so.
> 
>  
> 
> The K3 S-Meter shows S-6 to S-7, hmmm.
> 
>  
> 
> Should I be adding 10+log(K3 bandwidth/P3 resolution) to my P-3 view to
> compare with K-3 S-Meter? 
> 
>  
> 
> +/- 10 KHz span: P3 resolution = 20,000/450 = 44.4 Hz
> 
> K3 bandwidth = 2700 Hz (stock filter)
> 
>  
> 
> 10*log(2700/44.4) = 17.8 dB
> 
>  
> 
> -110 dBm +17.8 dB = -92 dBm or around S-6.
> 
>  
> 
> 
> 
> AE6WA
> 
> Mike Scott
> 
> Tarzana, CA
> 
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