[Elecraft] [K3] ideas for re-purposing our old K3 synthesizers

[Wayne Burdick]

Hi Steve,

Not to throw cold water on this, but.... the original KSYN3 requires a ton of firmware support, including a hand-tweaked table of thousands of PLL divider values pre-calculated and stored in flash memory. We shoehorn the DDS reference signal through a 3-kHz wide crystal filter in order to ensure no close-in spurs, then adjust the PLL divider values in real time so there are no gaps in the tuning range despite a nominal 20-kHz PLL step size. Lots of idiosyncratic math, and a critical calibration step ("VCO CAL"). 

So if each of your repurposed KSYN3s comes with a K3 front panel MCU and flash, no problem :)

73,
Wayne
N6KR


On Jun 24, 2015, at 7:18 PM, inventor61 . <inventor61 at gmail.com> wrote:

> I printed out the schematic of the original K3 synthesizer module.  The
> diagram says 'rev. A4' and is dated 8 Jan 2010.  Hope that's close to the
> as-built!  (probably is)
> 
> This gizmo appears to have an output range from 8.7 to 46 MHz.  I don't
> know how much sauce it can develop but I have to imagine +10 dBm or so into
> 50 ohms, I bet it's flat across that range, and it looks like the thing
> would be whistle-clean.
> 
> To get that, it needs a tight 49.38 MHz reference oscillator (I found a
> 0.5PPM TCXO for ~$30 from mainland China), and several common DC supply
> voltages.
> 
> It also needs a small microcontroller or other way of providing the correct
> serial peripheral interface command lines and interaction.  That processor
> would also control the output frequency, perhaps with an encoder, or
> whatever human interface might make sense….