[Elecraft] [KX3] SWR Reading Instability Follow-up

[Mark Petiford]

Re:  Can you redo the 1-2-1-2 test with FM?

I just duplicated the original test with my KX3 (FW 1.94/1.28) and got the same results.  I repeated the "1-2-1-2" voice test and the SWR remained stable as it did in AM as well. 

It looks almost like the KX3 is calculating the SWR using a good current value for forward power (dropping off to zero as the voice trails off between syllables or words) but using a stale value (not updated often enough) for reflected power.  When the forward power goes to zero or near zero as it does on SSB between syllables, it doesn't take much reflected power to give you the appearance of high SWR if you are using a stale reflected power value.  In AM and FM, the carries remains relatively high stabilizing the calculation by never letting forward power drop to, or near, zero between voice syllables.  

Of course, it could also be related to the time constants in the hardware, but now I am speculating too much...and being a hardware guy, I love to blame things on the software guys!  ;-)

Mark
KE6BB