[Elecraft] VFO calibration

[Ron D'Eau Claire]

Helm is quite right about WWV not being the "absolute" standard for
frequency and time. 

All serious measurement system calibration in the USA is traceable to
the National Institute of Standards and Technology (NIST). They are
responsible for providing the standards against which every sort of
measurement that is made in the USA can be compared, including frequency
and time. NIST runs station WWV, but WWV is not the most accurate source
of frequency and time information. The NIST standards are so good that
they are actually degraded by the propagation effects of the radio waves
from WWV traveling at essentially the speed of light. 

MOST signal generators, even very expensive ones, aren't any better than
the accuracy of the WWV signal, but it is a lot easier to calibrate them
using a "secondary standard" in the shop than it is listening to a
signal off of the air. The problem for us Hams is that few of us have a
reliable "secondary standard" that is as good as WWV, so we go to the
trouble to use the WWV signal whenever possible. 

The whole business of "measuring" something is a scientific discipline
in itself. The process of taking data and understanding what it means
goes far beyond putting a probe on a circuit and looking at a readout.
NIST publishes a very interesting booklet on the subject that doesn't
require a math degree to follow. It's available on-line at:
http://ts.nist.gov/ts/htdocs/230/233/calibrations/Publications/exp_meas.
pdf.  It's not radio-oriented, but covers the subject of how to make
measurements and analyze the results, including some simple experiments
that can be carried out with home-made equipment to demonstrate the
process. 

An important point that most of us realize intuitively is that the
accuracy of the measurement need only be good enough for  the task at
hand. In the case of aligning the K2, if we set the 4.000 MHz oscillator
within a several Hz we will have set it many times more accurately than
the K2 design is capable of maintaining. Therefore, any errors we find
afterward are a result of trade-offs in the K2 design and not in our
alignment methods. In simple words, "It's as good at it gets". 

Of course, some of us start wondering, "I wonder if it could be
better...", but that's a different story. As Helm put it so well, "This
rig is a hobby unto itself." 

It sure can be to those of us who like to tinker. 

And for those who simply want a rig that works very well "On the Air"
day in and day out, it does that too as many ops with "stock" K2's have
often testified on this reflector. 

Ron AC7AC
K2 # 1289


-Someone mentioned that all counters are calibrated against WWV.  I
don't know where that urban (or rural) legend came from.  If you think
that down at H-P techs are zeroing in counters with an old Grundig tuned
to 10 Mc. you're off....-Helm.