K2 Alignment

[Tom Field]

I've been using my K2/100 for a couple of years, and have been very
satisfied. I have noted some drift in the freq, so decided to go through a
complete realignment process.

On Page 65 of the manual it describes a measurement of the BFO range as
being 4-6 kHz. I measure 3.52 kHz. Question one, is this sufficiently out
to be of concern? and question 2, what are the next steps to correct any
problem?

Tom
KN6DR
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[vk2rq]

It is a bit on the low side, but may still be ok. Where the limited range could become a problem is in the filter alignment stage. You could try continuing and see how it goes; if the restricted range prevents you from aligning the filters properly, then some attention to the BFO circuitry may be required.

73, Matt VK2RQ




On Sat, Jul 11, 2015 at 10:48 AM -0700, "Tom Field" <[hidden email]> wrote:










I've been using my K2/100 for a couple of years, and have been very
satisfied. I have noted some drift in the freq, so decided to go through a
complete realignment process.

On Page 65 of the manual it describes a measurement of the BFO range as
being 4-6 kHz. I measure 3.52 kHz. Question one, is this sufficiently out
to be of concern? and question 2, what are the next steps to correct any
problem?

Tom
KN6DR
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[Don Wilhelm-4]

Tom,

Your limited BFO range will only be a problem when aligning the IF
filters.  If you find you cannot align the filters properly, then you
will have to correct that problem, but it may be a case that you have a
marginal solder connection somewhere in the BFO area and re-flowing the
soldering will give you a wider range.  Look at the RF Board schematic
sheet 2 in the lower right corner to identify the components involved
with the BFO.

Typically the K2 does not drift but a few Hz after being given a bit of
a warmup period (10 or 15 minutes).
Proper dial calibration and drift are 2 different things.  Drift is the
frequency change over a short period of time, such as a single operating
session (usually do to temperature changes).
Dial Calibration can change over time, but typically does not vary much
because the calibration data is contained in EEPROM and does not depend
on any realtime reference oscillator for accuracy and consistency.

If your situation is really drift (by my definition above), then I need
to ask how old is your K2 (serial number please).  If it is SN 3000 or
below, does it have the A to B upgrades as well as the other Elecraft
mods installed.  There are 2 mod kits that are important for temperature
stability - the BFOMDKT and  E850138 (the PLL temperature compensation
mod - so called "thermistor mod").  Look at the BFO inductor L33 on the
bottom of the RF board - if it has many turns of fine wire and is held
in place by a 1/8 watt resistor, then you have the BFOMDKT installed.
Then look on the top of the RF board on the left side near the Control
Board for RP3 (it may be under the KDSP2 or KAF2 if you have those options).
If you see a small board with resistors on it in the RP3 location, you
have the "thermistor mod" installed.

Especially since you have the K2/100, if either of those mods are
missing, I suggest you install them.  In addition, if your K2 is below
SN 3000, you may want to consider doing the entire set of A to B upgrade
mods (I recommend it).

Once you have checked those mods, go on with your calibration and
alignment process.
For the K2 Dial Calibration and filter alignment, I suggest you use
Spectrogram or another audio spectrum analyzer for the best results.  
See my webpage www.w3fpr.com article on K2 Dial Calibration.

OK, I have given you more information at one time than you may have
wanted.  However, it is all related to dial calibration and drift
(again, two different things).  Work through it one step at a time, and
if you have questions as you go along, please ask.

73,
Don W3FPR



On 7/11/2015 1:48 PM, Tom Field wrote:

> I've been using my K2/100 for a couple of years, and have been very
> satisfied. I have noted some drift in the freq, so decided to go through a
> complete realignment process.
>
> On Page 65 of the manual it describes a measurement of the BFO range as
> being 4-6 kHz. I measure 3.52 kHz. Question one, is this sufficiently out
> to be of concern? and question 2, what are the next steps to correct any
> problem?
>
>

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[Bill Coleman-2]

> On Jul 11, 2015, at 1:48 PM, Tom Field <[hidden email]> wrote:
>
> I've been using my K2/100 for a couple of years, and have been very
> satisfied. I have noted some drift in the freq, so decided to go through a
> complete realignment process.
>
> On Page 65 of the manual it describes a measurement of the BFO range as
> being 4-6 kHz. I measure 3.52 kHz. Question one, is this sufficiently out
> to be of concern? and question 2, what are the next steps to correct any
> problem?

So long as you can set the filters properly, I wouldn’t worry about the BFO range. When I added the RTTY mode and set my filters for 1500 Hz center frequency, I had to pad the BFO with a small capacitor to get enough range.


Bill Coleman, AA4LR, PP-ASEL        Mail: [hidden email]
Web: http://boringhamradiopart.blogspot.com
Quote: "Not within a thousand years will man ever fly!"
           -- Wilbur Wright, 1901

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