[Elecraft] P3 Vs. K3 Noise Level

[Dave Cole]

Alan,
Thank you for such a clear explanation!  I understood the process, and
why, but having someone actually put numbers to it helps in getting
that "gut feeling" as to why...  Thank you!!
-- 
73's, and thanks,
Dave (NK7Z)

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On Mon, 2016-03-07 at 09:56 -0800, Alan wrote:
> The indicated noise level depends on the receive bandwidth.  For 
> example, if you use a narrower bandwidth on the K3, you'll notice
> that 
> the S meter reads lower.
> 
> The effective bandwidth of the P3 is approximately one pixel on the 
> display, which is SPAN/468.  So, for example, if the span is 47 kHz,
> the 
> effective bandwidth is about 100 Hz.  If the K3 bandwidth is 2.7
> kHz, 
> then the P3 should read 10 * log (2700/100) = 14 dB lower than the
> K3. 
> 14 dB is roughly 3 S-units.
> 
> When measuring a steady carrier, the K3 and P3 should read the same, 
> since all of the signal is within the bandwidth.  The P3's amplitude
> can 
> be calibrated with the "Lvl Cal" menu selection.
> 
> Alan N1AL
> 
> 
> On 03/07/2016 03:14 AM, Brian J. Linn wrote:
> > All:
> > 
> > 
> > 
> > Even after considering the P3 manual (page 21) and with AGC off, I
> > find the
> > following difference in S unit measurement odd.
> > 
> > 
> > 
> > 
> > 
> > Band  P3    K3
> > 
> > 75m   S5    S9
> > 
> > 10m   S0    S2
> > 
> > 
> > 
> > 
> > 
> > I'm trying to ascertain an accurate noise level reading at my
> > QTH.  Does
> > anyone have any thoughts on the degree of difference in these
> > readings?
> > 
> > 
> > 
> > Brian KD0HII
> > 
> > 
> > 
> > 
> > 
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