[Elecraft] K3 Hardware Updates

[Ron D'Eau Claire]

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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