[Elecraft] K3 Hardware Updates

[Eric Swartz -WA6HHQ, Elecraft]

I apologize, but Ron is incorrect.

You MAY make the diode/resistor termination mod without changing the but 
timing in the menu. It has no negative impact in eother case.

73, Eric  WA6HHQ
====

Ron D'Eau Claire wrote:
> Eric and my statements are quite correct, both of them!
>
> If you add the diodes and resistors per the App Note, which provide better
> termination on the synthesizer control lines, you *must* change the SPI bus
> clock rate to "SP2" for proper (stable) operation.
>
> V 3.24 (or later) firmware has a menu command that allows you to change the
> SPI bus clock rate as needed. 
>
> The K3 works perfectly with that change, but with much reduced noise while
> turning the VFO on the 6, 10 and 60 meter bands, at least for those who
> experienced the noise. 
>
> A few people have downloaded the newer firmware (3.24 or later) and tried
> changing the SPI clock rate without installing the diodes and resistors that
> terminate the synthesizer control lines. Doing that leads to unstable
> operation. 
>
> Similarly, I installed the diodes and resistors (while illustrating the App
> Note), forgot to change the SPI clock rate, and found my VFO unstable. 
>
> After some head-scratching I realized my oversight, changed the SPI bus
> clock rate to "SPI 2" and everything is perfect again.
>
> So the K3 is perfectly stable without installing the parts, no matter which
> version of the firmware you install, provided you leave the menu command for
> the SPI Bus rate at CONFIG:MD SPI 1. 
>
> Similarly  the K3 is perfectly stable with the diodes and resistors
> terminating the synthesizer control lines provided you change the SPI bus
> rate to CONFIG:MD SPI 2
>
> Ron AC7AC
>
>
>
> -----Original Message-----
> From: elecraft-bounces at mailman.qth.net
> [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Joe Planisky
> Sent: Sunday, August 23, 2009 6:24 PM
> To: Elecraft Reflector
> Subject: Re: [Elecraft] K3 Hardware Updates
>
> Now doggonnit, let's get our stories straight!
>
> Ron D'Eau Claire says:
>
>   
>> ... if you add the resistors and diodes and do not
>> change the timing, the VFO may become unstable,
>>     
>
> Eric Swartz says:
>
>   
>> There is no downside to making this h/w mod, even if you do not enable
>> the menu option.
>>     
>
> Am I missing something, or are these two statements contradictory?   
> Maybe Wayne can be the tie-breaker :-)
>
> 73
> --
> Joe KB8AP
>
>
>
> On Aug 23, 2009, at 4:08 PM, Ron D'Eau Claire wrote:
>
>   
>> Well, it shouldn't hurt to do the mod, but I agree with David if you  
>> can't
>> find any noise.
>>
>> The reason 3.24 is required is that it provides a menu entry for  
>> changing
>> the bus timing as described in the procedure. A slightly different  
>> timing is
>> required for stable operation once the diodes and resistors are added.
>>
>> If you try to load the firmware and change timing without adding the
>> resistors and diodes, or if you add the resistors and diodes and do  
>> not
>> change the timing, the VFO may become unstable, making un-commanded  
>> QSYs.
>> (On my K3 they were in 100 Hz steps.)
>>
>> The default timing in all the firmware, including 3.24 and up, is  
>> correct
>> for K3's that do not have the diodes and resistors added, so you  
>> need do
>> nothing after upgrading your firmware if you haven't added the  
>> parts. Your
>> K3 will continue to work FB just as always.
>>
>> A revised mod procedure will be posted Monday to make that point  
>> clear.
>>
>> Ron AC7AC
>>
>>     
>
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