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

[Mike Markowski]

So it does!  And to think of all my unnecessary REF LVL adjusting.  One of these days I'm going to have to spend more time with that thing called a manual. 

Thanks and 73,
Mike ab3ap,  who -thought- he read it through.

On Jan 3, 2012, at 11:39 PM, Alan Bloom wrote:

> 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