[Elecraft] [K3] VFO tuning noise reduction mod results?

[Eric Swartz - WA6HHQ, Elecraft]

The h/w mod does not really impact the noise at all. It is required 
though and is there to maintain reliable signaling between the main 
processor and the synthesizers when the CPU to Synct serial bus speed is 
increased with SPI=2.  Its the change to SPI=2 that reduces the noise.

this can also be impacted by how you built the K3. The tightness of 
screws and proper grounding of the PC boards can impact this, as can the 
location of the synth to mixer coax cables. Seethe manual for proper 
location.

73, Eric  WA6HHQ



Joe Planisky wrote:
> I have the VFO encoder noise on the low end of 10M.  Yesterday, I  
> applied the VFO tuning noise reduction mod and switched to SPI 2 in  
> CONFIG:VCO MD.  That seems to have reduced the tuning noise a little,  
> but not as much as I'd expected (or hoped).  The noise was a solid S3  
> before the mod, but now shows up as bobbling between S2 and S3, so  
> call it a 1/2 S-unit improvement.
>
> I've triple checked the component locations and they're definitely  
> soldered to the correct vias as shown in the instructions (Rev C).   
> The diodes are oriented in the proper direction as shown.  I've  
> checked the values of the resistors and forward/reverse direction on  
> the diodes and all is as it should be.
>
> To others that have the noise and have applied the mod, is this in  
> line with your results?
>
> 73
> --
> Joe KB8AP
>