[Elecraft] K3 S-Meter and Noise

[Don Wilhelm]

Dan,

That behavior is common for many receivers - the K2 and K3 included.  
Admittedly, a few do it differently and the RF Gain will reduce the 
S-meter reading rather than sliding the scale upward.
The reason is that the RF Gain works in 'parallel' with the AGC.  In 
other words, the developed AGC voltage and the RF Gain voltage is 
applied to the same circuits, and the way the S-meter is implemented, 
there is no way to distinguish between them.

Each operator must make a decision - if the S-meter reading is the most 
important consideration, the RF Gain must be set at the full CW 
position, but if maximum receiver dynamic range is more important, the 
RF gain will be reduced and the S-meter reading will be a relative 
reading rather than an accurate scale.  The difference between (say) S-5 
and S-7 will still be 2 bars, but they will appear at the S-7 and S-9 
marks instead of the S-5 and S-7.

If you are doing weak signal work or working on a crowded band, I 
suggest you opt for the maximum dynamic range by reducing the RF Gain 
(and advance the AF Gain) so you can just barely hear the band noise.  
But if your current operation is more casual, run the RF Gain at max and 
you will have valid S-meter readings.

73,
Don W3FPR

AB3EN wrote:
> Don, 
>
> I notice that if I have the RF gain less than full CW the S Meter bars are
> progressively lit and it looks like the noise level has increased when it
> has not. The latest beta is a work of art and should make folks happy but
> the S Meter / RF gain interaction puzzles me. Out of habit I do not run RF
> gain full out, but for a more accurate meter I guess I will. Can you explain
> the interaction?
>
> Dan
> AB3EN
>   
>