[Elecraft] Want Pro test/alignment Insts. for K2

[Don Wilhelm]

Peter,

It seems that you really want to fully test every circuit in your K2 when
you complete it as would be done in an engineering level test.  That testing
level has already been done in many cases, but I do not think the results
have been published - nor do I expect them to be.

OTOH, as Andy said - if you have the equipment and do take the readings of
your 'typical' K2, others having adequate equipment also may be moved to do
the same, and I am certain Wayne and Eric would like to have the results
available to post on the Builder's Resource webpage.

If you have no problems, you likely do not need the signal generator, but a
spectrum analyzer and tracking generator that sweeps the RF in sync with
displaying the demodulated audio range would be a much better tool to set
the filter/BFO combinations than a wideband noise generator and Spectrogram.

The K2 usually works, and the suggested techniques use tools that are
commonly available.  You can use better tools if you have them available and
it does make the task a bit easier - assuming you already know how to use
those tools.  As an example, I use my 'scope to monitor the RF output when
doing the SSB carrier balance adjustment rather than another receiver - it
just makes more sense to me and I can do the task more quickly.

There are actually few things to adjust on the K2 - the bandpass filters are
one thing, and the transmitter serves as a good generator for that -
something 'analog' reading to judge the peak is easier than using the K2
LED, and that is what 'scope displays are for when you have them - nothing
fancy required.

There is one adjustment that you could improve on if you have access to a
signal to noise ratio meter - and that is the adjustment of L34.

An accurate frequency counter makes setting the reference oscillator right
at 4 MHz a snap, but then using the 5th harmonic of the reference beat
against a 20 MHz WWV signal will achieve results that are as good - it just
takes a bit longer.

Other than that - there are not a lot of alignments to do.

So for my part, one does not need expensive well calibrated equipment when
building a K2, but if you have it, the job is easier.

73,
Don W3FPR

----- Original Message -----

Hi, uh...Peter? I know I sent you a reply on this subject when I
saw your musings on it several weeks back, and I just forget your first
name.

> Also, have the designers published expected AF/RF voltages
> (or dbm) for given frequency(s) at:

You'd need to know what level signal input or power output to
set up for, but --

> VCO Input to Rcv mixer?
> Lo input to Rcv mixer?
> Output from Rcv mixer?
> LO input to Tx mixer?
> VCO input to Tx mixer?
> Output of Tx mixer?
> Input to 4.915 Mhz Xtal filter
> Output from 4.915 Mhz Xtal filter?
> IF amp input?
> IF amp output?
> Product detector input?
> Product detector output?
> Pre Driver input?
> Driver input?
> PA input?
> PA output?
> For 1000 Hz input, what is expected AF output?

-- those are all good points to know about. In fact, they would
have helped me when my newly-built K2 had low sensitivity
that seemed to center around Q22.

I am sure Eric and Wayne haven't published such a list (or even better
yet, some digital oscilloscope captures) because in general, the K2
alignment consists of "peak-for-max" or "set for this DMM value" and
the 3500+ (isn't that neat?) K2s out there work fine when aligned
that way. And they're too busy making new products! Or perhaps having
a life. It's easy to forget that the Elecraft company isn't a team of
a dozen or more designers.

But your point (and my experience) are well taken: when the rig is
suspected of NOT performing up to par, such a table would be a great
help. It could also save a field return from going to Gary Surrency.

There is the genesis of such a list in the back of the K2 manual, in
the signal tracing section, where you build a simple oscillator and
check voltages with the Elecraft RF probe supplied with the K2s.
I wound up using an old military signal generator to do my tracing.

There are also some scope-shots on the Elecraft site someplace,
under "signal tracing," done by a K2 owner.

(Here's a suggestion: I think it's Don Brown who does the noise source
kits - why not spin a new version that also has a 7 MHz xtal osc for
just such a purpose?)

Peter, it sounds like YOU will have the equipment to take such measurements.
Maybe, after your K2 is built, you could check those signals and publish
them for everyone? It wouldn't be as good as hearing it directly from
Elecraft, but it would be "something." My gut feeling is that your K2,
like the 3500 others, would be performing fine and your table or scope
shots would be "good" ones. It's a start. I certainly wouldn't lean on
Elecraft to provide such a list unless they have run out of new things
to design and are bored in the lab. :-)

Andy