[Elecraft] Example - Re: P3 auto REF LVL adjust?

[Alan Bloom]

The P3 already does this if you have MENU:SpanScale set to anything
other than "OFF".

Alan N1AL


On Tue, 2012-01-03 at 19:52 -0500, Mike Markowski wrote:
> I'll follow up on my own note because there's nothing as helpful as an 
> example:
> 
>    1) I move to 17m band with P3 set for +/-100 kHz span
>    2) P3 REF LVL knob used to set -122 dBm to match noise level at my QTH
> 
>    3) -122 dBm = 6.30957 x 10^-13 mW
>    4) Since noise power N = kTB,  (k is Boltzman's constant),
>       T = N / (kB) = 6.30957 x 10^-13 / (k x 200 kHz)
>       k = 228500 K    <--- recalc when REF LVL knob is twiddled again!
> 
>    Now I want to change P3 span to +/-5 kHz, or B = 10 kHz:
> 
>    5) N = kTB = (1.380648813 x 10^-23) x 228500 x 10x10^3
>         = 3.15479 x 10^-14 mW
>         = -135 dBm    <--- new REF LVL setting, send to P3
> 
> Easy to add to firmware?  If not, it is easy to add to external 
> software.  The only thing not automatic is that the initial manual REF 
> LVL setting is required to take into account antenna system noise 
> presented to the P3.
> 
> I hope other REF LVL twiddlers find this useful.  73,
> 
> Mike ab3ap
> 
> On 01/01/2012 03:26 PM, Mike Markowski wrote:
> > Since the PA temp is available as well as the filter bandwidth in use, I
> > wonder if the P3 could have an auto-adjust of REF LVL? It would only
> > work within a given band and only after the op has adjusted the REF LVL
> > to begin with. But after that it seems that the good ol' N = kTB would
> > be a simple enough calc that P3 REF LVL could be auto-adjusted as SPAN
> > or filter bw is changed.
> >
> > I know, talk about being lazy... :-) Happy 2012!
> >
> > Mike ab3ap
> 
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