VFO tuning noise reduction mod results?

[Joe Planisky]

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



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[Eric Swartz - WA6HHQ]

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
>  

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[K2QI]

Hi Joe,

The mod in my case removed an S2-S3 tuning hash from 60m completely.  I
can't hear anything while spinning the VFO now, even with no antenna
connected.

73 de James K2QI

On Wed, Aug 26, 2009 at 12:57 PM, Joe Planisky <[hidden email]> 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
>
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>

--
73 de James K2QI
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[Joe Planisky]

It seems you were right, Eric.  I had my K3 open for surgery recently  
to install the KRX3.  Of course, that involved lots of repositioning  
of the coax cables.  I also took the opportunity to make sure all the  
internal screws were tight.  When I got everything back together, the  
encoder noise on 10M was gone (at both SPI 1 and 2).  I still had a  
little at the bottom end of 6M, but setting SPI 2 completely  
eliminated it.  I'm happy.

73
--
Joe KB8AP


On Aug 26, 2009, at 10:28 AM, Eric Swartz - WA6HHQ, Elecraft wrote:

> [...]
> 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).

[...]
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