[Elecraft] Frequency Shift

[Ron D'Eau Claire]

You will hear a very small change in pitch - and sometimes no change in
pitch - when you have all the filters lined up. 

The circuits themselves have a potential error of about 30 Hz. That's
the resolution of  the digital to analogue converters (DACs) that turn
the digital levels into the analogue tuning voltage needed to set the
BFO on the desired frequency. You can often get closer than that, but
potentially the tone could shift as much as 30 Hz from one filter to
another .

If you'd like to try to get them closer, just run through CAL FIL again
(be sure to insert the probe in the test point on the r-f board) and
force the K2 to recalculate all the BFO tuning voltages. You do that by
going into CAL FIL, displaying the BFO frequency by pressing the DISPLAY
button or displaying the DAC setting by pressing the ANT 1/2 button, and
then turn the tuning knob to change the frequency, then put it back .The
fact that the frequency control was moved causes the K2 to "think" you
changed the frequency and it will recalculate tuning voltage needed to
set the BFO correctly. Maybe this time it gets it a little closer <G>.

Ron AC7AC
K2 # 1289


All -

Finished K2 serial number 3194 this week and enjoying the radio.  As
with anything new, you notice things and wonder if they all act that way
or it's just yours.

That's especially true when you build it yourself.

Here's what I noticed, changing filters changed the pitch of the signal.
Mode is CW.  Pitch of incoming received signal (I used WWV for testing)
is shown on Spectrogram at:

Filter     Width     Pitch of Signal       Change
FL1        150           608
FL2         70            576                     32 hz.
FL3         40            581                       5 hz.
FL4         10            581                       0 hz.

The only one I really notice is the change from FL1 to FL2.  Suspect it
may have to do with my filter calibration.

Either this is typical or it's just mine.  Comments?

Thanks in advance,
73 de NA8M
John

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