[Elecraft] RE: K2 Frequency Alignment

[Ron D'Eau Claire]

The 30 Hz error is common. The 80 Hz error may be normal too. I don't =
recall
the readout accuracy at 20 MHz, but it is not as good outside the Ham =
bands
as it is inside the bands. It's gotten a lot better with newer versions =
of
the firmware, so I don't recall offhand just how good it is and I =
haven't
heard WWV on 20 MHz in a while here.

Keep in mind that the K2 frequency display is NOT reading the actual K2
frequency. What you see on the LCD display is what the firmware =
calculated
the frequency should be when you last ran CAL PLL, not what the =
frequency
really is at the moment. There are some inherent errors in that system.=20

When you run CAL PLL, the actual frequency is measured by the internal
frequency counter. That's when it's important for the 4 MHz oscillator =
to be
right on 4 MHz, so the frequency counter will be as accurate as =
possible.
Any error in the 4 MHz oscillator while CAL PLL is being run will =
produce an
error in the dial calibration.

CAL PLL checks the K2's actual frequency at a number of points and =
creates a
look-up table that is used in normal operation. It's an electronic =
analog of
an mechanical dial using a pointer and paper scale with frequencies =
written
on it. To calibrate the "dial", the frequencies at certain points over =
the
range are actually measured and noted. The frequencies in between those
points are calculated based on assumptions about the tuning =
characteristic
of the oscillators. Any errors in the calculations will show up as =
readout
errors in normal operation.=20

In normal operation, the LCD frequency display can be "off" due to =
several
reasons:

1 - The accuracy by which the frequency was measured during CAL PLL. =
This is
affected by two things: The accuracy of the 4.000 MHz oscillator and the
resolution of the digital-to-analogue converters (DACs) used in the K2
logic. I believe the DAC's have a potential error of about 30 Hz, so any
dial reading more accurate than 30 Hz is a matter of "luck".=20

2 - Any "drift" in the VFO circuits after CAL PLL was run. CAL PLL =
builds a
table of tuning voltages that is stored in memory for future use. When =
you
tune the K2 in normal operation, the system assumes that if a certain
control voltage is sent to the oscillator, it will produce exactly the =
same
frequency in response that it did during CAL PLL. Any drift in the
oscillator will produce errors in the actual frequency.

Ron AC7AC
K2 # 1289=20

-----Original Message-----
I am using that method and thus the question. =20

The two traces are right on top of each other and I can even hear and =
see
the slow (about every two seconds) zero beat, Thus the thing is within =
less
than 1 hz off. =20

BUT, even after alignment this way, running call pll, etc.  WWV at 10 =
mhz is
off by 30 hz and WWV at 20 mhz is off by 80 mhz, after a 30 minute =
warm-up
and stays there.  BOTH 10 and 20 are right on top of the harmonic and
exhibit the same zero beat.

Do you need to set the clock for something other than =
4.00000000000000000 to
compensate for software counting inaccuracies.  It appears that the =
method
is the FCTR method and making both read the same frequency.=20

Rich