[Elecraft] 4mhz osc and Firmware change.

[Steven Gibbs]

Hi Ron, try this ...

1.  Set the K2 to about 9999.00kHZ USB.  On Spectrogram
you should see the WWV 10MHz carrier as a tone of about
1000Hz.  Ignore any tones WWV might be transmitting.

2.  Disconnect the antenna; you should see a weak signal
also of about 1000HZ - this is the tenth harmonic of a
1MHz signal derived by the MCU from its 4MHz clock (you
will recall that a similarly-derived 7MHz signal is used
in initial 40M alignment).  You can verify that you are
looking at the right signal by touching the Control Board
MCU crystal X2 or its associated components and noting that
the frequency on the Spectrogram display changes slightly.

3.  If WWV is coming through strongly there might be
enough breakthrough to show WWV's signal also.  Use an
insulated tuning tool (the Elecraft tool is rather poor
for this job) to adjust Control Board C22 so that the two
signals coincide - final proximity may show a beat which
can be reduced to zero.  If WWV isn't very strong you
won't see its breakthrough signal so you'll have to
alternately connect and disconnect the antenna until you
have the two signals giving the same frequency on
spectrogram.

4.  Note that the exact setting of the K2 dial and the
exact frequency on the Spectrogram display doesn't matter.
(The sidetone frequency which you use doesn't matter
either).  These are the important features of this method.

5.  It's a good idea to re-perform CAL-FIL.

6.  You must re-perform CAL-PLL.

7.  SPOT the WWV carrier in CW and again in CW-REV; in
each case the K2 dial should show 10000.00kHz probably
plus or minus about 20Hz.

8.  If you have a local frequency standard there's a
method of setting the MCU frequency with even more
certainty - my posting of 8 Sep 01, reproduced below.

73, Steve GU3MBS

====

If you have access to a 1MHz frequency standard, here's a method of
setting the K2's reference oscillator with greater certainty than
trying to zero-beat with WWV.  I used an off-the-air standard
derived from the high-accuracy carrier frequency of the BBC's 198kHz
LW transmission.

You will need a 4MHz bandwidth oscilloscope having a high-sensitivity
x-amp (5mV/div worked for me), with an independent trigger input
derived from your frequency standard.

1.  Temporarily reduce the x-amp sensitivity, connect to the trigger
source, and adjust the 'scope's timebase and trigger level to stably
display one or two cycles of the 1MHz standard frequency.

2.  Move the 'scope probe to the vicinity of X2-C21-C22 on the K2
control board, but do not touch anything, just rely on loose
capacitive coupling.  Connect the probe's ground connection to the
control board ground point.  Switch the 'scope to maximum x-sensitivity,
and look for a trace showing pick-up from the 4MHz clock oscillator.

3.  Use a non-metallic trimming tool (sorry, but the Elecraft tool is
pretty useless here) to carefully adjust C22 so that the scope trace
is resolved into a sine wave moving slowly or rapidly either to the
left or to the right.  Note that four cycles occupy the same time as
one cycle of the 1MHz reference oscillator.  Careful tuning will
result in a near-stationary display when the trimming tool is removed,
and the 'scope probe is gradually drawn away.  This indicates very
close matching of the K2's reference oscillator to four times the
standard frequency.  (A left or right shift of 4 cycles in one second
means the frequencies are matched to one part in a million.
Temperature effects will degrade frequency accuracy, so it's probably
not worthwhile trying for better than this).

4.  Remember that control board reference oscillator X2 does NOT
directly control K2's TX & RX frequencies.  You will have to
re-perform CAL PLL & CAL FIL.

4.  Connect the K2 frequency counter probe to TP1 and perform CAL PLL
(do this on each band if you have version 1 firmware).

5.  Connect the counter probe to TP2 and run through all the CAL FIL
parameters.  You may not have to change anything, but it is
necesssay for the firmware to recognise and remember any apparent
change in BFO frequency.  (Just to satisfy yourself, you might want
to connect up to a computer running the Spectrogram program to
re-check that everything is OK).

That's all folks.    73, Steve GU3MBS