Elecraft K2 Owner's Manual - Manual (Page 64)

E
LECRAFT ® 63
Alignment and Test, Part II
In this section you’ll test and align the PLL (phase-locked-loop)
synthesizer and receiver circuits. Once this is completed you’ll be able
to test the receiver using all modes on 40 meters.
Connect your power supply or battery and turn on the K2.
4 MHz Oscillator Calibration
Plug the frequency counter probe into P6 (Control board).
Connect the probe tip to the PLL reference oscillator test point,
TP3 (left-front corner of the RF board, near U4).
Using the menu, select CAL FCTR, then hold
E D I T
a second time to enable the frequency counter. The counter
should show a frequency of 12090 kHz +/- 30 kHz. If it is 0000.00,
changing rapidly, or out of range, you could have a problem with the
counter probe or the PLL Reference Oscillator.
Use one of the following methods to adjust C22 on the Control
board (listed in order of preference):
 Connect a calibrated external frequency counter probe to TP3,
without removing the K2's internal counter probe. Adjust C22
until the K2's reading matches the external counter's reading.
 Alternatively, you can use a calibrated short-wave or ham-band
receiver. Set the receiver for LSB or USB mode. Connect a short
length of wire to the receiver's antenna jack, and lay the end near
the 4 MHz crystal on the K2 Control board. Find the oscillator
signal on the receiver. Tune the receiver to 4.000 MHz, and adjust
C22 until you hear a zero-beat (pitch = 0 Hz).
 If you don't have a counter or receiver, leave C22 set at its mid-
point for now. You can improve the calibration later using a
calibrated signal generator or an on-air signal, such as WWV (at
10.000 MHz).
PLL Reference Oscillator Range Test
Set up the K2 internal counter as described for 4 MHz Oscillator
Calibration (at left, first three steps).
If you have an external frequency counter probe connected to
TP3 along with the K2's internal counter probe, disconnect it.
When you’re in frequency counter mode, the
B AN D +
and
B AN D -
switches can be used to check the range of the PLL reference
oscillator. First, tap
B AN D +
and write down the frequency reading
below (typically about 12100 kHz). Then tap
B AN D -
and write down
this frequency reading (typically 12080-12090 kHz).
Ref. High Freq.
Ref. Low Freq. Range (kHz)
____________ ____________ __________
Subtract the lower frequency reading from the higher reading.
The range must be between 9.8 and 15 kHz (if not, see
Troubleshooting). Tap
M E N U
to exit CAL FCTR.
VCO (Voltage-Controlled Oscillator) Test
Use
B AN D +
or
B AN D -
to select the 80-meter band, and set the
VFO for a frequency of about 4000.10 kHz.
Connect the frequency counter probe to the VCO test point, TP1.
Activate the frequency counter using CAL FCTR as before.
You should now see a frequency counter reading in the 8 to 10
MHz range. It may or may not be stable at this time (i.e., the frequency
may be changing). If the reading is 0000 kHz or is changing rapidly,
you probably don’t have the counter cable connected to the VCO test
point. If the reading is fairly stable but not between 8 and 10 MHz,
refer to Troubleshooting.
Tap
M E N U
to exit CAL FCTR.