Posted by
Don Wilhelm-3 on
Nov 11, 2005; 1:42am
URL: http://elecraft.85.s1.nabble.com/K2-Adjustment-Use-of-Test-Instrumentation-Alternative-Procedures-tp383581p383582.html
Howard and all,
I must respecfully disagree.
I have built many K2s and have aligned many others, and I can state from
that experience that the test equipment required is minimal. The techniques
in the current manual for setting the reference oscillator, especially the
technique offered by none other than Wayne Burdick himself using CAL FCTR
and alternating between TP1 and TP2 while tuned to WWV or some other known
frequency achieves superior results.
I use an accurate frequency counter, a DMM, a 'scope, and a computer loaded
with Spectrogram to accomplish all that is required for proper K2 alignment,
and even all that is not required - I consider the DMM and the computer with
Spectrogram as essential, the rest are convenience instruments (see below).
I would not use any additional equipment for the alignment tasks even if it
were available.
I happen to have acquired a frequency counter that is accurate to 10e-9 or
better, and it does the job of setting the reference oscillator easier (I do
not measure the reference directly, but compare the CAL FCTR reading
obtained at TP1 with my external counter), but is not more accurate than
checking the difference between the VFO and BFO while tuned zero beat to the
WWV carrier - I come within 20 Hz using either method.
For adjusting the bandpass filters (in transmit mode), I use my oscilloscope
to indicate the RF voltage at the antenna jack (across my dummy load). Used
in this manner, I am only using the 'scope only as a fast responding RF
voltmeter and it allows me to see the peak more readily - this is only a
convenience for me and not any necessity - an ordinary DMM with RF Probe or
the K2 display itself would be adequate, but would not respond as quickly,
so one would have to tune the slugs and capacitors more slowly.
For aligning the filters, I have found no better or more convenient method
than Spectrogram and the N-Gen although the N-Gen is a convenience too, most
any source of wideband noise (including 'dead band noise') would suffice
just as readily.
OK, so what do I use my array of other test equipment for? It certainly
comes in handy when I am troubleshooting a problem. The possibilities for
the use of various types of equipment for signal injection and signal
analysis can be quite lengthy, and must be coupled with an understanding of
what is normal and what is abnormal - one could write a lengthy book on all
the possibilities, but that is the challenge of troubleshooting in a
nutshell - one must understand not only what is to be expected, but must be
capable of interpreting what is unexpected. This is certainly not in the
league with normal K2 alignment.
The bottom line here is that additional test equipment may make the task
quicker and easier, it will accomplish no more than the procedures outlined
on the manual and on the Elecraft website - the use of substitute equipment
and techniques should be obvious to those familiar with the use of that test
gear. So if one is contemplating the purchase of test equipment just to
align the K2, I would say "save your money for other Elecraft goodies" - the
equipment you have already is adequate to do the task. OTOH, if you wish to
make things a bit easier and/or get involved with in-depth troubleshooting,
additional equipment may be a big assist, but you must know how to use that
equipment (and that is another chapter entirely). Consider your needs and
goals against your ham budget and make your decisions on that basis - a
'scope will only be an instrument to display 'pretty pictures' unless you
also gain the knowledge of how to properly interpret the waveforms shown, it
is all a learnog experience.
73,
Don W3FPR
> -----Original Message-----
>
> The K2 Manual, and various posts to the Elecraft website or this
> reflector, provide substantial information regarding K2 adjustment, c22
> calibration, filters, etc. These generally assume that one doesn't have
> access to test instrumentation beyond a DMM and the frequency counter
> built into the K2. This is laudable since it has allowed me, and many
> others, to build and calibrate a K2/100 without investing in an
> electronics lab. However, I have been slowly accumulating good test
> equipment to pursue various design and repair interests and will soon be
> going over my K2/100 and my KX1 using these tools. It would be helpful
> to have adjustment and calibration procedures available that
> alternatively assume the use of test instrumentation. Although one can
> admittedly figure a lot of this out yourself, having a procedure/check
> list reduces the possibility of error. And in some instances, the
> sequence of adjustment can be significant.
>
>
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