[Elecraft] N6KR's 4 MHz oscillator cal method for the K2

[Baker]

On Thu, 28 Aug 2003 09:31:42 -0400, Don Wilhelm wrote:
>Dave and all,
>
>I have reviewed Michael's report several times.  I have noticed
>several of
>the discrepancies that he reported, and am rapidly coming to=
 the
>conclusion
>that Wayne's method will yield better dial calibration than
>attempting to
>set the reference 'dead on' 4 MHz.  It appears that the=
 reference
>frequency
>must be set just a tad lower than 4 MHz, and Wayne's method does=
 not
>involve
>the exact frequency of the reference, only the difference in the=
 VFO
>and BFO
>frequencies.
>
>It produces good results while minimizing the variables.
>
>I will be putting the frequency stability mod in my K2 and=
 adding
>the 2.5
>kHz SSB filter mod, so I will get the opportunity to play with=
 all
>the CAL
>PLL and CAL FIL stuff once more.  I will let you know more=
 after
>those
>experiments.
>
>For those who may feel overwhelmed by all this discussion - it=
 is
>not as bad
>as it seems.  Not everyone has to play around with this stuff -=
 just
>do the
>steps that Wayne has mentioned, and you should end up with good=
 dial
>calibration.  Be certain that you do know what is meant by zero=
 beat
>before
>you start - it makes a big difference.
>
>73,
>Don W3FPR
>
>----- Original Message -----
>
>| Michael AG9V gave a detailed report on his investigation into
>| frequency calibration. I am not going to paste all of that or=
 give
>a
>| detailed description of my own attempts. The point it shows is=
 
that
>| the best accuracy you can achieve is within 10Hz on the lower=
 
bands
>| and rather more on the higher ones.
>|
>| I have not tried Wayne's method, but I am sure it works. My 
attempt
>| the other day (after my last posting) was briefly as follows:
>|
>
>
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Hi Guys

I have also found that Wayne's method produces a more accurate 
frequency calibration than setting the 4MHz reference 'dead on'.
I have been able to get most bands (up 14MHz to within 10Hz.

I finally settled for using my FT1000MP as a signal generator and=
 
measuring it's frequency on a counter that seems to be accurate=
 to 
1Hz. 

I found that by switching the AGC to FAST and adjusting the RF=
 Gain 
control I could get quite a good visual indication on the S meter=
 bar 
graph when approaching 'zero beat'. The bar graph strobes with=
 the 
beat frequency as one gets below about 25Hz. Using this method I=
 was 
able to get within 1 display count i.e 10Hz nominal.

This was using the SSB filter, so there must be enough LF signal=
 
getting through the filter to enable the AGC to respond to the=
 beat.

Hope this is of use

73

Stewart G3RXQ
-- The Bakers' Home
-- baker@nildram.co.uk on 28/08/2003