K2 Alignment

[k6dgw]

I've had some time to play with the brand new K2.  It appears to be
working great!  I actually read the manual and I think I might
understand the filter bandwith/BFO stuff and what CAL FIL is doing.  I
have a question or two ... off-reflector replies are probably
appropriate since the traffic on this reflector is high:

I left a lot of my hearing in SE Asia, but I have a "sweet spot" at
about 650 Hz or so for CW.  I'd like the pitch of the received station
to stay at that freq when I change filter BW's.  I succeeded in getting
it close for CW NORM -- sort of an iterative process.  I did finally
figure out that I needed to center the signal in the narrowest filter,
set the BFO for the right pitch, and then set it for each of the wider
filters.

1.  Should I be able to do the same thing for CW REV?  What I'd like is
that filter setting and NORM/REV have no effect on the pitch of the
signal centered in the passband.

I did a quick VFO calibration before I took the K2 to Alpine County for
CQP.  It is still about 250 Hz off, I think.  (The CQP Alpine County
expedition is a different long story!)

2.  Should I do a good VFO cal first, before fooling around in CAL FIL
or does it not matter?

3.  Based on the initial VFO cal, I have a suspicion that I'm at or near
the end of the range on C22 and might not be able to get it right on.
Other than the obvious display error, is this a factor in getting the
CAL FIL process completed?  Is there a way to fix it?

I have a calibrated service monitor.

FWIW:  9.9 W out on 10m, and over 10W on all other bands ... I wound the
toroids and binocular as stated in the book.  (This is on a 12V gel cell
for power).

Thanks to all for all the help during the construction, it was fun.  And
so is operating with it.

73,

Fred K6DGW
Auburn CA CM98

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[Don Wilhelm-3]

Fred,

The answers to your Dial Calibration and Filter Alignment should be found on
my website www.qsl.net/w3fpr.  As you have discovered, the numbers in the
manual are a good starting point, but you can do much better.  Calibration
resulting in no more than 30 Hz error is readily achievable with a bit of
care.

You can obtain the same pitch within 10 to 20 Hz when switching filters with
care in doing the alignment.  The use of an audio spectrum analyzer program
such as 'Spectrogram' and a wideband noise generator is highly recommended.

You will end up doing the dial calibration and filter alignment 'sort of'
together, because the dial calibration requires that you run CAL FIL after
the reference oscillator is changed.

73,
Don W3FPR

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

> I've had some time to play with the brand new K2.  It appears to be
> working great!  I actually read the manual and I think I might
> understand the filter bandwith/BFO stuff and what CAL FIL is doing.  I
> have a question or two ... off-reflector replies are probably
> appropriate since the traffic on this reflector is high:
>
> I left a lot of my hearing in SE Asia, but I have a "sweet spot" at
> about 650 Hz or so for CW.  I'd like the pitch of the received station
> to stay at that freq when I change filter BW's.  I succeeded in getting
> it close for CW NORM -- sort of an iterative process.  I did finally
> figure out that I needed to center the signal in the narrowest filter,
> set the BFO for the right pitch, and then set it for each of the wider
> filters.
>
> 1.  Should I be able to do the same thing for CW REV?  What I'd like is
> that filter setting and NORM/REV have no effect on the pitch of the
> signal centered in the passband.
>
> I did a quick VFO calibration before I took the K2 to Alpine County for
> CQP.  It is still about 250 Hz off, I think.  (The CQP Alpine County
> expedition is a different long story!)
>

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[Masleid, Michael A.]

Hi Fred,

> I have a calibrated service monitor.

Don's page has what you need to know.

Since you have a service monitor, there may be a shortcut.
The service monitor needs to be within 1 part per million.
I don't know if CAL FCTR has changed in the latest
firmware, but this used to work:

To set C22 with an accurate service monitor:
Let the K2 warm up.
Start CAL FCTR.
Set the service monitor to 28100 KHz.
Attach to the frequency probe.
(Connect the shield from the monitor
to one of the ground points on the K2.)
Increase output from the monitor to get
a reasonably stable count on the K2.
I needed about 1 Volt.
Set C22 so that you read 28099.95 on the K2.
The display may switch between 28099.95 and 28099.96.
That's all there is to it.
This creates a small offset to the 4 MHz oscillator
that is needed for some reason.

You have to do CAL PLL and CAL FIL with the bottom
cover in place, and the stand the way you want it
when you operate, and you have to do it before to
much time goes by, since the setting on C22 is
temperature sensitive.

73, de Michael, AB9GV
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[Ron D'Eau Claire-2]

Fred, I missed your first post, but have you checked the procedure for
setting C22 on the Elecraft web site (www.elecraft.com). It's under "Builder
Resource Page", then click on "How to "Build and Test Your Kit" under "Main
Topics" of the page, then click on, "Adjusting C22 to calibrate the K2's
Frequency Display".

This procedure provides calibration as accurate as the  K2 is capable of
based in the accuracy of the source. If you can hear WWV, it will be as
close as the K2's logic and WWV. You can't do better than that with any test
equipment, it's very simple and straightforward to do and requires no
external equipment whatsoever.

Ron AC7AC



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[Mike S-8]

At 10:40 PM 10/5/2004, Ron D'Eau Claire wrote...
>Fred, I missed your first post, but have you checked the procedure for
>setting C22 on the Elecraft web site (www.elecraft.com).

Just a warning. That article is out of date, and hence inaccurate. With current firmware it is not necessary to run CAL PLL on every band, just on 40 meters.

It's pretty hard to "zero beat" WWV in USB/LSB, since the AM carrier will become inaudible when you're anywhere close. The lower range of human hearing and bandwidth limitations get in the way.

This is what works for me: I find that tuning while bouncing between USB and LSB (hold CW REV to do so without having to cycle through the other modes) and matching the sound of the WWV marker tones works FB. When the tones match, you're on frequency (at least within ~20 Hz, the VFO+BFO cumulative error).

Wayne introduced a method which might work quicker for actually setting C22 ( http://www.qsl.net/w3fpr/n6kr_method.htm ): If you're tuned to 10 MHz WWV, set C22 so the difference between the VFO (TP1) and the BFO (TP2) is 10 MHz, run CAL PLL then CAL FIL, and you're done. In my experience, you actually want the VFO set about 10 Hz lower than theoretical.

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[Ron D'Eau Claire-2]

Egad! Thanks for catching that error Mike!

I have a copy of that procedure from an E-mail Wayne posted to the reflector
a year ago and it had the correct instruction to run CAL PLL on 40 meters
only! According to the e-mail he had just developed this procedure at that
time and the procedure was correct for the current firmware, so I never
thought to look at the one on the web site more closely.

Good catch!!

If anyone is confused about the CAL PLL issue, here's the original procedure
as published by Wayne August 20, 2003. It is correct:

-------------------------------------------------------------

This method relies on the following simple observation. If you tune in an
on-air
signal at a known frequency, the difference between the *measured* VCO and
BFO
(using CAL FCTR) *must* equal that frequency, or C22 is not set correctly.
(Actually, this holds for 160-17 m; on 15-10 m it's the sum, or VCO + BFO,
that
must equal the signal's frequency. But it's easier to do the adjustment of
C22
on 17 m or lower because you don't have to do any math at all, as I'll
explain
below.)

Here's the procedure. It requires revision 2.XX firmware, and assumes you
have
already done Alignment and Test, Part II, at some point. The K2 should also
be
allowed to come up to room temperature.

1. Tune in a signal at a known frequency. Use one that's at an *exact* kHz
boundary, so you can easily see when the VCO and BFO readings match in step
2.
(I use WWV at 10, 15, or 20 MHz.) Use USB or LSB mode rather than CW, so
that
there will be no CW receive offset. In the case of a K2 I was calibrating,
the
VFO read 10000.17 when the signal was tuned in perfectly. If it had read
10000.00, no further improvement would have been possible.

TIP: Zero-beat the carrier precisely, or listen to a voice signal and adjust
the
VFO for the best quality. The more accurately you tune in the signal, the
more
accurately you'll be able to set C22, below.

2. Run CAL FCTR. Now alternately move the K2's internal counter probe
between
TP1 (VCO) and TP2 (BFO), adjusting C22 in small increments until the kHz and
Hz
digits at the two test points match as closely as possible. In my case, the
two
readings matched at 14913.60 and 4913.60. The difference is exactly
10000.00--the frequency of the on-air signal.

3. Put the counter probe on TP1 (VCO), switch to 40 meters, and run CAL PLL.

4. Put the probe on TP2 (BFO) and run CAL FIL. For each operating mode, vary
each filter (or BFO) setting up 1 count, then back down, to force the K2 to
take
a new BFO measurement for each and store it in EEPROM.

The VFO dial should now be very well calibrated.

If we get a lot of positive feedback on this method, we'll post it as an
application note.

73,
Wayne
N6KR
--------------------------------------------

It's a mystery how the old CAL PLL procedure got put in there...

Ron AC7AC




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[Don Wilhelm-3]

Confusion reigns!!!

There are 2 articles on the Elecraft website about setting C22.  One is old
(it even says 'updated', but says to run CAL PLL on all bands - don't use
that one!!
Instead, download the Frequency Calibrating the K2's 4 MHz Master Oscillator
(C22).pdf article in the "What's New" section of the Builder's Resource
area -- THAT IS the N6KR method that you need.  Wayne's original posting
content is on my website too www.qsl.net/w3fpr.


I guess Eric missed deleting the old procedure when the new one was posted.
Forgive him, he has a lot of stuff going on.

73,
Don W3FPR

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

Egad! Thanks for catching that error Mike!




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