[Elecraft] K2 w/KSB CW reverse BFO

[Don Brown]

Hi

The only reason you need to set the 4.000 Mhz oscillator is so the firmwa=
re can set the VFO look up tables to make the dial read correctly. The 4 =
Mhz oscillator is not used for anything except running the MPU at any oth=
er time and could be set anywhere and it would not matter to the operatio=
n of the K2 or the calibration. The only time it needs to be accurate is =
when CAL PLL is running. As the Frequency counter is only used to set the=
 CAL PLL and the filters during setup it only makes sense to set it so th=
e VFO is the most accurate it can be and if that is exactly 4.000000 then=
 so be it, but if it needs to be a few hertz one side or the other to mak=
e CAL PLL set the VFO right then that's where I will set it. The procedur=
e that I use or the one using another receiver are the only ones that do =
this. A frequency counter is only as accurate as it's internal time base =
but even if it is right on it may not set the VFO to the best place. I ha=
ve seen several K2 setup with a frequency counter that I was able to impr=
ove with my method.

Don Brown
KD5NDB

----- Original Message -----
From: k6se@juno.com
Sent: Thursday, October 31, 2002 8:05 PM
To: elecraft@mailman.qth.net
Subject: Re: [Elecraft] K2 w/KSB CW reverse BFO

KD5NBD wrote:

"This procedure for setting the 4.000 MHz clock is right out of the
Elecraft manual page 98 and it does put the 4.000 MHz clock on frequency
calibrated to WWV."
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
Note that page 98 lists the methods of adjusting C22 on the control board
in order of preference.  Using WWV is the least desireable method, which
is why it is listed last.

Page 98 refers to page 57 where the 4 MHz oscillator calibration is
described in detail.  The #1 preferred method is to use an external
calibrated frequency counter.  If an external counter is not available,
the alternate method is listening to the oscillator on a receiver capable
of accurately tuning to 4.000 MHz while you tune C22.

The only place WWV comes into play here is that the test receiver must be
calibrated using WWV's signal to ensure that it is accurate at 4000 kHz.

I say again, I was told by Elecraft that calibrating the 4 MHz oscillator
to exactly 4000.000 kHz is how it should be done for greatest accuracy
for the built-in frequency counter.  Adjusting C22 so that the VFO
readout is accurate per KD5NDB's method will most likely have the result
that the 4 MHz oscillator is not exactly on 4000.000 kHz.

Because the K2's VFO frequency accuracy drifts with changes in
temperature, why worry about VFO accuracy anyway?  The specs say drift is
less than 100 Hz in an environment where the ambient temperature is
stable.  Drift can easily exceed 100 Hz when the ambient temperature
varies, so why bother?

73, de Earl, K6SE
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