[Elecraft] K2: Help, I messed up the dial calibration!!!

[Don Wilhelm]

Steve,

Yes, the "4 MHz" reference may have to be set a few Hz different than 
exactly 4.00000 MHz to calibrate the dial accurately.

The best method I know of is to feed the K2 audio into a computer 
running Spectrogram.  This method compensates out any difference between 
4 MHz and the actual required frequency for the reference - one does not 
even need to be concerned about the reference frequency with this method.

On the Spectrogram line display, set markers (pointers) for 500 and 600 Hz.
Now tune WWV in LSB (or USB if you prefer) - 10, or 15 MHz, either is OK 
- 20MHz requires a bit of a difference in the VFO/BFO calculation due 
the the sum of the oscillators rather than the difference.

When you look at the Spectral line display of the WWV transmission, you 
will see the carrier (only if you are mistuned), and a transmitted tone 
(wait until the do transmit a tone).  The tone is normally either 500 or 
600 Hz, but there is a 440 Hz tone for one minute each hour and there 
are some non-tone minutes.  You can look up the transmission format on 
the web and it will tell you which minute is which tone - or you can 
just wait and watch the tones alternate.  The short tone transmitted for 
one second at the beginning of each hour is always1000 Hz, so I move the 
cursor to 1000 Hz (read the frequency in the lower left box of the 
screen) and click to place a crosshair at 1000 Hz too, it is a handy 
reference if WWV is weak ir the other tones are not clear.

Now that you have the Spectrogram 'picture' of WWV and have identified 
the relevant tones in the audio (the carrier, and one of the transmitted 
tones), tune the VFO first listening until the voice sounds rather clear 
- then you may see the carrier near zero Hz and the tone near the 500 or 
600 Hz marker that you have set.  Tune the VFO until the tone is lined 
up exactly with the marker.  Wait until the next tone minute to be 
certain you are tuned correctly and not 100 Hz off.

Enter CAL FCTR, then check to see if the tones are still lined up - you 
can fine tune a bit if necessary, but when you have the VFO set 
correctly (for the tones, not the dial reading - the dial reading will 
not be correct - that is why you are going to all this trouble).  Do not 
move the VFO after this, you will next be adjusting C22.
Now, you move the probe between TP1 and TP2 until the frequency 
difference is exactly equal to the WWV transmitted frequency.  Since WWV 
transmitts on 0000.000 kHz boundaries, just look for the low order 
digits to be the same at TP1 and TP2.  If the digits are not the same, 
adjust C22 a bit and see if the frequencies got closer.  Once C22 is 
adjusted correcctly, the low order digits of the BFO (TP2) and the VFO 
(TP1) will match exactly, and you can declare that C22 is now set 
exactly right - do not touch it again.

Now, switch to 40 meters and run CAL PLL followed by CAL FIL (change 
each BFO setting even if it is correct - moving it up a bit and back 
down to where it was constitutes a 'change' to the K2.
Once that has happened, you are done.
Tune WWV again as before and note the dial setting - you should find it 
no more than 20 Hz off.  The DAC limit of tuning varies with frequency, 
but averages about 13 Hz, so 20 Hz is within the expected practical 
tolerance limits.

It takes a LOT more time to write this than it does to do it - it is 
easier to do than to say.

73,
Don W3FPR

Steve Kallal wrote:
> Don,
>
> Sorry I didn't fully read your comments before my first reply.
>
> Could you briefly explain how you calibrate with the 500 & 600 Hz 
> markers? Can it be done in real time while tweaking C22? I can't do 
> it. I have C22 set exactly to 4 MHz via the 20 MHz WWV method, with a 
> perfect zero beat. Yet, I am about 40 Hz off on WWV 10 MHz. Apparently 
> there is more than setting the clock to exactly 4 MHz followed by CAL 
> PLL/CAL FIL.
>
> If you have some canned document of the 500/600 Hz tones Spectogram 
> method , let me know.
>
> 73,
>
> Steve N6VL
> K2/100 #2289
>
> Don Wilhelm wrote:
>> Steve,
>>
>> Your steps are correct.
>>
>> It sounds like you are off by the amount of your sidetone pitch.
>> Were you receiving WWV in LSB or USB mode?  If you used CW mode, that 
>> would explain the difference.
>>
>> Are you quite certain that you tuned WWV accurately?   Do not 'set 
>> the dial at 10,000.00', but instead, ignore the dial and tune until 
>> WWV is received correctly.  I use Spectrogram for that with markers 
>> (pointers) set at 500 and 600 Hz for that.   When correctly tuned, 
>> you will see the tones alternate each minute from 500 to 600 Hz (yes, 
>> I know there are no-tone minutes, and one minute shortly after the 
>> hour is 440 Hz, but mostly they alternated between 500 and 600 Hz.).
>>
>> When done correctly (mostly tuning WWV accurately), you results will 
>> be within 20 Hz of WWV.  One cannot expect much better than that due 
>> to the DAC resolution used in the K2.  I do this most every day, and 
>> it has become 'old hat' to me - use Spectrogram to verify the correct 
>> tuning - ignore the K2 dial display until the last verification step.
>>
>> 73,
>> Don W3FPR
>>
>>
>>
>> Steve Kallal wrote:
>>> I was trying to calibrate my K2/100 and had it within 10 Hz 
>>> according to WWV 10 MHz. I should have left it alone. Now it is off 
>>> by about 700 to 800 Hz on 40 meters. Ouch!
>>>
>>> Here are the steps I did so far:
>>>
>>> 1. I set the C22 trimmer on the Control Board by the N6KR method at 
>>> http://w3fpr.qrpradio.com/n6kr_method.htm. I set the dial at exactly 
>>> 10.000.00 MHz, and alternated between TP1 & TP2 until the readings 
>>> CAL FCTR match with about 2 Hz.
>>>
>>> 2. I ran CAL PLL.
>>>
>>> 3. I ran CAL FIL on every mode / filter combination, being sure to 
>>> change the BFO hex value even if not needed.
>>>
>>> I didn't build the K2 in the first place. So I never did the entire 
>>> procedure before.
>>>
>>> Any help is welcome!
>>>
>>>
>>
>
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