[Elecraft] External Frequency Reference for K2 or 3

[Don Wilhelm]

Andrew,

That would not make the K2 dial reading any better than it is already.
The K2 does *not* use the 4 MHz reference on a real time basis for the 
dial frequency reading.

It *might* be useful during the CAL PLL and CAL FIL process which is 
when the K2 stores the frequency related data into EEPROM for use during 
actual operation.  In normal operation, the 4 MHz reference oscillator 
is only used as a clock for the microprocessor and its actual frequency 
is not critical.  It *is* critical that the 4 MHz reference oscillator 
be set accurately just prior to a CAL PLL and CAL FIL operation if good 
dial calibration is to be achieved.  The best method to achieve an 
accurate setting is to use the method documented in "Frequency 
Calibrating the K2's 4MHz Master Oscillator (C22)" on the Elecraft 
website at 
http://www.elecraft.com/Apps/K2%20C22%20Adjust%20App%20Note.pdf  -- this 
method does not require any external equipment, it only requires that 
the K2 be receiving a signal having a known frequency.  In most areas of 
the world, a good standard station can be heard.  WWV and WWVH are good 
choices but there are others.
The K2 dial calibration can be in error by as much as 20 Hz even when it 
is as 'correct as it can be' because that is near the DAC resolution limit.

The K3 does have provision for using an external reference, but it is 
not functional in the firmware yet.

73,
Don W3FPR

Andrew UK wrote:
> Hi does anyone knowif there are or were there any plans to introduce and
> external frequency reference input (1Mhz or 10 MHz)  to the K1,2 or 3, as
> Rubidium and GPS off air standards  are very cheap now days? and would make
> a nice addition to the accessory line up.
>
> If not, I can easily generate a 4 MHz sine wave signal does anyone know the
> best palce to inject it into the K2? assuming the 4MHz assuming U6 clock is
> the master clock for the system.
>
> 73's
>   
>