[Elecraft] K3: Question about S-Meter Calibration

[Lyle Johnson]

> So, the S-Meter calibration instructions in the manual indicate that  
> PRE should be on.  When calibration is done,  that means that a 50uV  
> signal reads S-9 with PRE on .. but about S-7 with PRE off.  And then  
> if the mode is changed from Normal to Absolute, a 50uV signal reads  
> S-7 with or without the preamp.

Yes.  In the end, you must calibrate the S Meter for how you use it. I 
operate in ABS mode, so I have PRE OFF and ATT OFF when I do the S Meter 
cal using a -73 dBm (50 uV) source.  I could leave PRE ON in thie mode, 
but I know that the DSP is adding an offset when I do that (as it does 
for ATT), so I calibrate with both OFF.

If I then go to the "other" S Meter mode, it is inaccurate, of course.

> Just wondering (maybe I need to RTFM and specs again), why that would  
> be the case, vs. 50uV being S-9 without the preamp.  I have always  
> just ignored the instruction manual, and calibrated to S-9 with the  
> preamp off.  So a 50uV signal reads S-9 (with or without preamp  
> engaged if the mode is Absolute).

Correct.

***

When you do the RF Gain Calibration procedure, it is important to know 
that your signal source is -73 dBm (50 uV).  If you use the S Meter to 
make this determination, you need to know how it was calibrated.


73,

Lyle KK7P