[Elecraft] K3 Hardware Updates

[Brett Howard]

Actually I believe that the signals will be plenty stable if you place
the hardware mod but don't change the frequency.  However speeding
things up (using the SPI2 setting) w/o proper termination is going to
cause problems.  

I think the reason for the speeding up of the clock was to put the
harmonics out of the bands.  The previous frequency was 1Mhz where as
with SPI2 its set to 4Mhz.  That puts the harmonics at 4Mhz, 8Mhz,
16Mhz, 32Mhz (and then we are out of the range of the rig).  Notice that
none of these fall inside of Ham bands..  You'll also note that the
areas where you are told to look for the noise is at the even 1Mhz
multiples.  

The diode and R combo allows for the R's to only be in play when the
Chip Select for those particular components is activated (low).  Its a
pretty darn slick idea.

~Brett (KC7OTG)

On Sun, 2009-08-23 at 16:08 -0700, 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
> 
> -----Original Message-----
> In a recent message, Roy Morris <w4wfb at carolina.rr.com> wrote ...
> >
> >Now that my K3s have v. 3.25 firmware,
> ...
> >  While I have access to the PCB, why not go ahead and install the VFO 
> >tuning noise reduction mod even though I do not experience noise during 
> >VFO rotation on 6, 10, and 60 meter bands.  You might say "if it ain't 
> >broke, don't fix it".
> 
> The mod notes for the VFO Tuning Noise Reduction do say, in bold type..
> 
> "IMPORTANT:  You must complete the modification as described below 
> before using firmware version 3.24 or later. Failure to do so will 
> result in erratic behavior of your K3."
> 
> That seems to imply that even if you don't notice to be broke, it may 
> be.
> 
> 73