98 ELECRAFT
Frequency Calibration Techniques
The VFO is only as accurate as the 4.000 MHz oscillator on the
Control board, which is calibrated using C22. C22 can be fine-tuned
using one of the following methods:
Using an External Counter or Ham-Band Receiver:
These methods are described in detail in Alignment, Part II (4 MHz
Oscillator Calibration). After setting C22 using either
technique, you must re-run C A L P L L (with the counter probe on
TP1). You'll also need to use C A L F I L (with the probe on TP2)
to re-adjust each BFO setting, which will allow the K2 to store new,
more accurate BFO frequency measurements.
Using a Calibrated Signal Source:
You can calibrate C22 using a signal generator, ham transmitter, or
strong AM carrier such as WWV at 10 MHz. The K2’s receiver is
used to zero-beat this signal to determine how far off the VFO is,
then C22 is adjusted to compensate. Because of the way C A L
P L L works, you can only use a signal source that is at one of the
lower band edges, e.g. 7000.00 or 10000.00 kHz. Here's the
procedure:
1. Select LSB or USB mode on the K2.
2. Zero-beat the calibrated signal source on the K2, then note the
VFO dial error. For example, 10 MHz WWV might zero-beat at
10000.20 kHz. The error is then 10000.20 - 10000.00 =
+0.20. Do not move the VFO from this position.
3. Connect the K2's internal counter to the VCO test point
(TP1).
4. Select and activate C A L F C T R using the menu.
5. Note the displayed VCO frequency. (In this example, 14913.88
kHz. Your VCO frequency will be somewhat different.)
6. Subtract the VFO dial error from the VCO to obtain a target
VCO frequency. (In our example, 14913.88 - 0.20 =
14913.68.)
7. Adjust C22 until the VCO is at the target frequency.
8. Re-run C A L P L L (see Calibration Functions). Tap
M E N U to
exit C A L P L L when "End" appears.
9. Move the counter probe to TP2 (BFO). Using C A L F I L ,
change the BFO control parameter for the filter presently
being used by at least one count, then return it to the original
setting. Tap
M E N U to exit without switching filters. This will
force the K2 to re-measure the BFO frequency.
10. Repeat step 2. If the VFO dial is still off, repeat steps 3 - 9.
11. Modify all BFO settings using C A L F I L (as in step 9).
Firmware Revision Numbers
You can check the K2's main microcontroller and I/O
controller firmware revisions by holding in any switch on power-
up. Two numbers will then be displayed briefly. For example, you
might see 2 . 0 3 A 2 . 0 4 . The first number is the main
microcontroller's firmware revision and letter suffix. The second
number is the I/O controller's firmware revision.
The ATU's firmware revision is one of the parameters in the ATU
submenu, e.g. F 1 . 0 0 . This also applies to the KPA100. The SSB
adapter's firmware revision can be obtained by first setting the
S S B A menu entry to B A L , then holding the
V O X switch. (Return
the S S B A menu entry to its normal setting after checking the
firmware revision.)
The firmware revisions for other options may also be accessible;
refer to the individual option manuals.
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