[Elecraft] SETTING THE K2 REFERENCE OSCILLATOR

[Dave Van Wallaghen]

Hi Al,

The VFO tuning of the K2 is drivin by its low phase noise PLL and a 
lookup table (created by CAL PLL) as well as the values stored for the 
BFO settings (CAL FIL). Therefore, after adjusting the 4MHz oscillator 
via C22, those routines must also be run as they depend on the new 
crystal frequency you just adjusted (with the exception of CW mode - see 
Don's explanation on his website).

If adjusted correctly, you may be able to get the VFO withing 20Hz. Don 
Wilhelm (W3FPR) has a web page that explains this operation and offers 
some background as to the K2 VFO design and operation concerning this 
adjustment. He also lists some other alternative methods.

For the adjustments I do for the K2's that come across my bench, I run 
CAL FCTR and use the probe to measure the output of my Leo Bodnar GPSDO 
with one port set to 20MHz. I adjust C22 until the LCD display matches 
20MHz (this is fairly tough to do as C22 is not very granular). But 
after I get it set, I then run CAL PLL and the CAL FIL where I go 
through each filter for each mode and adjust the frequency up and then 
back down to the original value. This causes the routine to rewrite the 
entry. The key to this adjustment is allowing the K2 to reach a steady 
operating temperature.

You can find Don's page here: http://www.w3fpr.com/dial_cal.html

73,
Dave W8FGU

------ Original Message ------
From: "W4RAM" <w4ram at outlook.com>
To: elecraft at mailman.qth.net
Sent: 6/5/2020 4:59:13 AM
Subject: [Elecraft] SETTING THE K2 REFERENCE OSCILLATOR

>Good morning,
>I am looking for assistance to be able to properly complete the reference
>oscillator calibration.
>
>Situation: despite moving C22 I don't see any change or correction when I
>try to zero beat signal from RWM (9,996.00)
>
>Performed procedure:
>1. I tuned the K2 with the RWM signal. I was able to "zero beat" in 9,998.25
>LSB (diff. +2.25).
>2. I connected the internal counter from P6 to TP1.
>3. I adjusted C22 (moved counterclockwise)
>
>I did not continue with Run CAL PLL and CAL FIL.
>I am using vertical HF external antenna.
>
>Thank you for any advice.
>
>V/R
>
>Al
>W4RAM
>
>
>
>
>
>
>--
>Sent from: http://elecraft.365791.n2.nabble.com/
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