K2 cannot calibrate dial

[Bartek SQ5OBP]

Hi,

I've bought nice K2 recently, SN >6900, and was trying to calibrate the
dial.
Carrier at 3856kHz was zero-beaten (LSB) when dial showed 3855,6kHz and I
could not get any closer with C22 adjustment.
C21 is in place.
What can be wrong?

73,
Bartek SQ5OBP
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[Mike K8CN]

Hi Bartek,

I suggest you try W3FPR's dial calibration method if you have not done so already.  You can find it at Don's web page http://w3fpr.com/ under the left side menu, "Setting the K2 Dial Calibration."  If you only adjust C22 and do not run CAL FCTR, CAL BFO, and CAL FIL as described by N6KR and W3FPR, you will not have reset the stored DAC values from which the actual frequency display is computed.

I finally tried Don's method this past summer after using my K2 for nearly 4 years -- it made a huge difference from my initial hasty calibration in the excitement of putting the rig on the air for the first time!

73,
Mike, K8CN

[Bartek SQ5OBP]

Hi  Mike,

I've bought my K2 already built and calibrated but the seller warned me he
could not get the dial calibrated well.
I have tried Don's method already but I cannot get dial any closer than
500Hz to the real frequency. I have run CAL PLL and CAL FIL and dial offset
did not decrease.
I wonder if C21+C22 capacitance in my K2 is large (or small?) enough to
change X2 frequency accordingly.

73,
Bartek SQ5OBP
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[Bartek SQ5OBP]

2012/3/13 G3TJP, Dave <[hidden email]>

> ** **
>
> Hello, Bartek.****
>
> ** **
>
> Very occasionally you will get a **K2** that won’t calibrate.  I have
> just sorted one out for another ham here in G-land.****
>
> ** **
>
> Sometimes a little more capacitance is required, sometimes a little less.
> In this instance, C22 was at minimum capacitance and the oscillator was
> running on the low side of 4MHz.****
>
> ** **
>
> I changed C21 from 33pF to 22pF NP0and when the trimmer was set to mid
> capacitance, the oscillator was a few Hz off 4MHz, giving me adjustment on
> both sides of 4MHz.****
>
> ** **
>
> It’s easier if more capacitance is needed because all you need to do is
> tack an NP0 capacitor across the trimmer or C21.  ****
>
> ** **
>
> If about 10pF up or down doesn’t give the required adjustment, consider
> replacing the 4MHz xtal****
>
> ** **
>
> A frequency counter is a real boon in situations like this.****
>
> ** **
>
> Don’t forget, ALWAYS run CAL PLL and CAL FIL after an adjustment of the
> 4MHz oscillator.  If the filters look OK, always move the setting up or
> down a digit so when you exit CAL FIL the new data for each filter is
> stored.  Even if the filter setting appears to be unchanged, it will have
> an effect on the frequency interpolation and can affect the frequency
> accuracy by a few Hz.****
>
> ** **
>
> 73  Dave **G3TJP******
>

Hello Dave,

Thank you for your response. I will try to arrange a calibrated counter and
check frequency range of the oscillator and possibly replace C21 or xtal. I
do remember to run CAL PLL and CAL FIL every time I change oscillator
frequency.

73,
Bartek SQ5OBP
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[Don Wilhelm-4]

Bartek,

Is it possible that you are using a standard station that transmits only
a carrier rather than an AM signal with tones like WWV is doing.  You
MUST be in SSB mode when using that method to set C22.  The fact that
you are off by 500 Hz suggests to me that you may be trying to use CW
mode and that your sidetone pitch is set to 500 Hz.

If you must use a station that transmits only a carrier, tuning the
station properly is a little more difficult, but can be done.  If that
is your problem please let me know, and I can give you a work-around.

73,
Don W3FPR

On 3/12/2012 6:27 PM, Bartek SQ5OBP wrote:

> Hi  Mike,
>
> I've bought my K2 already built and calibrated but the seller warned me he
> could not get the dial calibrated well.
> I have tried Don's method already but I cannot get dial any closer than
> 500Hz to the real frequency. I have run CAL PLL and CAL FIL and dial offset
> did not decrease.
> I wonder if C21+C22 capacitance in my K2 is large (or small?) enough to
> change X2 frequency accordingly.
>
> 73,
> Bartek SQ5OBP
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>

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[Mike K8CN]

Hi Bartek,

Presuming that you can see some response (frequency display change) when you vary C22, you might try the following procedure:

1) Re-set C22 to its mid-point setting (the default option in the Alignment and Test, Part II, p. 63 of the Rev. H manual)

2) Repeat the PLL Reference Oscillator Range Test, (also page 63)

3) Repeat the VCO Alignment (page 64) and especially note the VCO control voltage measurements, which
should be within the indicated range (here I'm presuming you have access to a DMM).

4) Repeat the BFO Test (page 65) and especially verify that the BFO High and Low frequencies as well as the BFO Range are within specifications. (It was at this stage in my own K2 test and alignment that I found a problem with an intermittent connection to L33 and an insufficiently low BFO Low frequency).

A measurement of the 4.0 MHz Reference Oscillator frequency with an independent, well-calibrated counter is a worthwhile step.  However, if the BFO frequency range is not within the specifications, you may find this to be the source of your problem.  You may find that in performing N6KR's 4.0 MHz Reference Oscillator alignment procedure, step 2, (I did this with the 10.0 MHz WWV signal) that you can't get the last 4 digits of the VCO and BFO frequencies to agree when you adjust C22, which may stem from inadequate or offset tuning ranges for either of these oscillators.

Let us know what you find!

73,
Mike, K8CN

[Bartek SQ5OBP]

Hi Mike,

Thank you for your invaluable help!
After re-setting the C22 to its mid-point position I have done all the
basic alignment steps in Part II of the Manual.
PLL reference oscillator range, VCO test, VCO alignment and voltage
readings, BFO range: all within specified ranges.
After CAL FIL and CAL PLL I tuned some stations on 80m and... voila!
No RIT needed to zero-beat most SSB stations, carriers of AM stations zero
beat at even kHz on both sidebands.
Right now I do not need better 4MHz oscillator calibration!

73,
Bartek SQ5OBP
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[Bartek SQ5OBP]

Hi Don,

I was using SSB mode to set C22. My CW sidetone was set to 600Hz.
After all, after re-setting C22 to its mid-point position I have done all
the basic alignment steps from Part II of the Manual and done CAL FIL and
CAL PLL and the problem was resolved.
Thanks for your help guys!

73,
Bartek SQ5OBP
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[Don Wilhelm-4]

Bartek,

I am happy o hear of your success.
If you attempt that in the future and must use a carrier of known
frequency as your standard, let me give you some information on how to
counter the K2 RX offset during that procedure.

73,
Don W3FPR

On 3/13/2012 6:00 PM, Bartek SQ5OBP wrote:

> Hi Don,
>
> I was using SSB mode to set C22. My CW sidetone was set to 600Hz.
> After all, after re-setting C22 to its mid-point position I have done all
> the basic alignment steps from Part II of the Manual and done CAL FIL and
> CAL PLL and the problem was resolved.
> Thanks for your help guys!
>
> 73,
> Bartek SQ5OBP
>

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[Mike K8CN]

Hi Bartek,

Glad all worked out well with the re-alignment - enjoy your K2!

73,
Mike, K8CN