ELECRAFT K2 User manual

Alignment Instructions
Extracted from the K2 Manual
By Don Wilhelm W3FPR

Setting the AGC Threshold Exit the CAL S HI function by tapping MENU.
Make sure the RF GAIN control is rotated fully clockwise.
Locate potentiometer R1 on the Control board (right side, as
viewed from the front of the K2).
Set your DMM for DC volts. Connect the (-) lead of the
DMM to one of the ground jumpers or to the K2 chassis ground.
Touch the (+) lead to pin 5 of U2 on the Control board. (U2 is
located just above trimmer R1. Pin 5 is the pin nearest diode
D1.)
Adjust R1 for a reading of 3.80 volts on the DMM. This is the
suggested setting, but it can be adjusted later to suite the
operator.
i The S-meter must be realigned anytime
the AGC
threshold setting is changed. S-meter
alignment is covered
in the following steps:
S-Meter Alignment
Using the menu, select the CAL S LO function (S-meter
zero). Hold MENU a second time to activate it.
Turn the VFO knob until you see only the left-most segment
of the LED bargraph lit. Then turn the knob a bit more clockwise
until this LED just turns off.
Exit the CAL S LO function by tapping MENU. Enter the
menu again and select CAL S HI (S-meter full-scale
sensitivity).
Turn the RF GAIN fully counter-clockwise (minimum gain).
Adjust the VFO knob until you see segment 9 of the bar graph
lit,
then turn it a bit more counter-clockwise until segment 10 just
turns on (right-most segment).
Turn the RF GAIN control back to its full clockwise position.
1

4 MHz Oscillator Calibration PLL Reference Oscillator Range
Test
Plug the frequency counter probe into P6 (Control board).
Connect the probe tip to the PLL reference oscillator test Set up the K2 internal counter as described for 4 MHz
point, TP3 (left-front corner of the RF board, near U4). Oscillator Calibration (at left, first three steps).
Using the menu, select CAL FCTR , then hold
MENU a second time to enable the frequency counter. The
counter
If you have an external frequency counter probe connected to
TP3 along with the K2's internal counter probe, disconnect it.
should show a frequency of 12090 kHz +/- 30 kHz. If it is
0000.00,
When you’re in frequency counter mode, the BAND + and
changing rapidly, or out of range, you could have a problem with BAND - switches can be used to check the range of the PLL
the counter probe or the PLL Reference Oscillator. reference oscillator. First, tap BAND + and write down the
frequency
Use one of the following methods to adjust C22 on the
Control board (listed in order of preference): reading below (typically about 12100 kHz). Then tap BAND -
and
 Connect a calibrated external frequency counter probe to
TP3,
write down this frequency reading (typically 12080-12090 kHz).
without removing the K2's internal counter probe. Adjust
C22
Ref. High Freq. Ref. Low Freq. Range (kHz)
____________ ____________ __________
until the K2's reading matches the external counter's reading.
Subtract the lower frequency reading from the higher reading.
 Alternatively, you can use a calibrated short-wave or ham-
band
The range must be between 9.8 and 13 kHz (if not, see
Troubleshooting). Tap M E N U to exit CAL FCTR .
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).
1

VCO (Voltage-Controlled
Oscillator) Test VCO Alignment
In the following steps you’ll adjust the VCO inductor (L30) so
that
Use BAND + or BAND - to select the 80-meter band, and set the
the VCO control voltage is in the proper range.
VFO for a frequency of about 4000.10 kHz.
Disconnect the internal frequency counter probe and remove
Connect the frequency counter probe to the VCO test point,
it completely from the K2.
TP1. Activate the frequency counter using CAL FCTR as
before.
Select 80 meters, and set the VFO for about 4000 kHz.
You should now see a frequency counter reading in the 8 to 10
Connect a DMM (digital multimeter) to the left end of resistor
MHz range. It may or may not be stable at this time (i.e., the
R30 (near the center of the synthesizer area of the RF board) and
frequency may be changing). If the reading is 0000 kHz or is
ground. Use a small alligator clip to ensure a good connection.
(You
changing rapidly, you probably don’t have the counter cable
connected to the VCO test point. If the reading is fairly stable
but can also use the built-in voltmeter to measure the VCO control
voltage. Refer to Voltmeter Probe Assembly in Part I.)
not between 8 and 10 MHz, refer to Troubleshooting. i It is possible to damage the slugs in slug-tuned inductors if
Tap MENU to exit CALFCTR .
you use a metal tool or if you tune the slug too far in or out. The
tuning tool provided will not damage the slugs.
Using the wide end of the plastic tuning tool, adjust the slug in
inductor L30 until the voltage at R30 reads 6.0 V. If the
voltmeter
reading does not change at all as you tune L30 through its full
range, refer to Troubleshooting. If the voltage changes but you
cannot get to 6.0 V, you have probably wound the VCO inductor
(T5) incorrectly or have installed the wrong value at L30 or C72.
Set the VFO for approximately 3500 kHz.
Measure and write down the VCO control voltage at this
frequency in Table 6-1 (using pencil).
For each remaining band, set the VFO to the low and high
frequencies listed in Table 6-1 and write down the VCO control
voltages.
(You can tune quickly to the approximate frequencies in
2

BFO Test
the table by selecting the 1-kHz tuning rate.)
The BFO (beat-frequency oscillator) will be tested in the
following
Table 6-1. VCO Voltage Readings
Band Low Freq. Voltage High Freq. Voltage steps.
80 m 3500 ______ 4000 ______
40 m 7000 ______ 7300 ______ Switch to the 40-m band.
30 m 10000 ______ 10150 ______
20 m 14000 ______ 15000 ______ Connect the frequency counter to the BFO test point (TP2),
17 m 18000 ______ 18200 ______ which is on the right side of the RF board near the crystal filter.
15 m 21000 ______ 21450 ______ Using the menu, select CAL FCTR . The counter should show
12 m 24800 ______ 25000 ______ a frequency between 4908 and 4918 kHz.
10 m 28000 ______ 28800 ______ i If you see a reading of 0000.00 kHz or one that is
changing rapidly, you may not have the frequency counter probe
If some VCO control voltage readings above are < 1.5 V, or connected properly, or the BFO may not be working (see
some of them are > 7.5 V, you may be able to shift the entire set
of Troubleshooting). If you see a stable frequency reading that is
nowhere near 4908-4918 kHz, you may have installed the wrong
readings so that they are all within the 1.5 to 7.5 V range. Switch
to crystals in the BFO (X3/X4).
the band (and frequency) that had the highest or lowest voltage,
When you’re in frequency counter mode, the BAND + and
then adjust L30 to bring that reading into range. Then re-measure BAND - switches can be used to check the range of the BFO.
First,
all of the voltages to make sure they're in range.
i If you have some voltages that are < 1.5 V and others that tap BAND + and write down the frequency reading below
(typically
are > 7.5 V, you have probably installed the wrong value at one
or about 4916-4917 kHz). Then tap BAND - and write down this
more of the VCO capacitors (C71-C74) or varactor diodes (D21- frequency reading (usually about 4909-4912 kHz). Finally,
calculate
D26). Another possibility is that T5 has the wrong number of
turns the BFO range (high - low) in kHz. Typical range is 4 to 6 kHz.
or that you installed the wrong type of slug-tuned inductor at
L30.
BFO High Freq. ___________ (must be >= 4916.3 kHz)
If you change any of these components, repeat the VCO
alignment BFO Low Freq. ___________ (must be <= 4912.7 kHz)
Range (High - Low)___________ (must be >= 3.6 kHz)
procedure.
If your BFO range is less than 3.6 kHz, you may have the wrong
Disconnect the DMM from R30. varactor diodes installed at D37 or D38, or the wrong crystals
installed at X3 or X4.
3

BFO Alignment
If the BFO frequencies are shifted too high or too low, it may be
due to one of the following:
The K2 uses a variable-bandwidth crystal filter, allowing the
 If you didn't calibrate the K2's internal frequency counter
using operator to set up as many as four filter bandwidths for each
operating mode. Each of these filter configurations requires an
an external counter, it may not be reading accurately. If appropriate BFO setting, which determines the pitch you hear.
possible, borrow an accurate counter and re-do the 4 MHz Filter and BFO set up is done with the CAL FIL calibration
Oscillator Calibration. function. CAL FIL is described in detail in the Operation
section
 The BFO range shift could be due to the inductance of L33 of the manual, under Calibration Functions. Rather than
duplicate
being too high or too low. However, since L33 is supplied
prewound this information here, the instructions and example in the
and tested, this is unlikely. Operation section will be used.
 The leads of R116 may have been heated excessively
during Make sure the bottom cover is securely attached.
soldering, shorting out a portion of L33's turns. Tap PRE/ATT until the PRE annunciator is turned on.
(Turning the preamp on will provide some background noise so
you
 One of L33's leads could be broken. Look closely at the
leads can hear the effect of changing filter bandwidths.)
using a magnifying glass.
Follow all instructions on page 85 to become familiar with the
 One or more of the capacitors or varactor diodes in the BFO CAL FIL function.
circuit could be of the wrong value.
Perform the steps in the example on page 86 to set up all
filters. You'll use the filter and BFO data from Table 8-1 (for a
CW-only K2), since the SSB adapter is not installed. If you later
install the SSB adapter, you can easily change the settings to take
advantage of the optimized, fixed-bandwidth SSB filter.
4

VFO Linearization I.F. Amplifier Alignment
Make sure the bottom cover is securely attached. L34, located near the right front corner of the RF board, is used
to
Allow the K2 to stabilize for at least 10 minutes at room peak the output of the I.F. amplifier.
temperature (approx. 20-25°C). (Note: Avoid using a high-
wattage
Using the wide end of the plastic tuning tool, adjust the slug in
L34 until it is near the top of the can. Stop turning the
slug
work lamp direct above the K2 during calibration. With the top
cover removed, this could heat the RF board to a higher when it appears to be at the top or when
you feel resistance.
temperature than would ever be seen during normal operation.)
Connect the internal frequency counter cable to the VCO
output test point (TP1). Turn L34’s slug one full turn clockwise (down into the can).
Use the procedure listed below to linearize the VFO. If you see Set the band to 40 meters using BAND + or BAND - . Select CW
any INFO messages, refer to Troubleshooting. Normal and FL2 (700 Hz nominal bandwidth).
1. Use BAND + or BAND - to select 40 meters. Select CW normal Make sure the RF GAIN control is fully clockwise (max. gain).
mode and filter FL1.
Disconnect the antenna from J4, if one was connected.
2. Set the VFO to anywhere in the range 7000-7100 kHz.
Tap PRE/ATTN until the PRE annunciator turns on.
3. Enter the menu and select CAL PLL , then hold a
second time to start the VFO linearization sequence. Connect a pair of headphones (stereo or mono) to the front
panel jack, and turn the AF GAIN control to about midway.
4. The frequency counter will show the VCO frequency as it
decreases through a range of about 10-13 kHz. (The letter "d " Slowly tune the VFO to locate the weak internally-generated
will flash each time a calibration data point is stored.) signal near 7000 kHz. If you can't hear the signal at all, you may
have a receiver problem. Try the 40-meter Band Pass Filter
5. When calibration is completed (4-8 minutes), you'll see the Alignment, below, then refer to Troubleshooting if necessary.
message End on the LCD. You can then tap any switch to
return to normal operation. If you see an INFO message rather While listening to the signal at 7000 kHz, adjust L34 for best
than End , refer to Troubleshooting (Appendix E). signal strength and lowest noise. This setting occurs at about 1 to
1.5 turns below the top of the can. (You can use your DMM on
AC
volts, at the speaker jack, to obtain a more sensitive indication.)
5

40-Meter Band Pass Filter
Alignment
Connect an antenna or a signal generator to the antenna jack
on the rear panel. If you use a signal generator, set it for approx.
7150 kHz at an output level of about -100 dBm, or strong
enough
to activate the S-meter. If you're using an antenna, tune in a
signal
in the range of 7100-7200 kHz. If you cannot find a signal, you
can use atmospheric noise from the antenna to peak the filter.
Using the plastic tuning tool, adjust both L1 and L2 (back left
corner) for peak signal strength. You may be able to use the
bargraph if the signal is strong enough. If you do not hear any
signals or noise, see Troubleshooting.
i In CW mode, the frequency shown on the display takes into
account an offset equal to your sidetone pitch. This allows you to
determine a station's actual carrier frequency by matching their
pitch to your sidetone, rather than by zero-beating the signal. The
SPOT switch can be used for this purpose.
6

Alignment and Test, Part III
In this section you’ll complete alignment and test of the K2 on all
bands.
Make sure the power switch, S1, is in the OFF position (out).
Connect your power supply or battery. For transmitter tests, a
battery or well-regulated power supply that can handle at least 2
amps is recommended. Avoid using a switching power supply
unless
it is well shielded and includes EMI filtering. A linear-mode
supply
will typically generate much less noise in the HF bands. (See any
recent ARRL Handbook for examples of both types.)
Connect a 50-ohm dummy load to the antenna jack. The
dummy load should be rated at 10 watts or higher.
Connect a pair of headphones and a key or keyer paddle.
Set the POWER control fully counter-clockwise (minimum
power output).
Turn on the K2. You should see ELECRAFT on the LCD,
followed by the frequency display.
Select voltage/current display mode by tapping DISPLAY to
make sure the receiver is not drawing excess current. (Typical
current drain will be 180-250 mA depending on menu settings.)
Return to frequency display mode.
Switch to CW and select FL1 using XFIL.
Use the menu to set up the desired CW sidetone volume and
pitch if you have not already done so, using ST L and ST P.
The
pitch can be set from 400 to 800 Hz, although 500-600 Hz is
recommended. The sidetone volume and tone will vary a small
amount as the pitch is changed, but it should have a pleasant
sinewave sound at any setting.
Set up the desired keying device using INP. If you’re using a
hand key or external keyer, use INP HAND. To use the internal
keyer, select PDL n or PDL r (normal or reverse paddle).
You can also connect a computer or external keyer along with
the keyer
paddle. Refer to the Operation section for details on this
"autodetect"
feature (Page 92).
To verify that the sidetone is functioning, hold the SPOT
switch.
Tap any switch to turn the SPOT tone off.
7

40-Meter Transmitter Alignment Tap any switch to exit.
i To align the transmitter you’ll need some means for If necessary, repeat the adjustment of L1 and L2 two or three
monitoring power output as you adjust the band-pass filters. An times to be sure that you have the inductors peaked correctly. If
analog wattmeter or oscilloscope is ideal. However, in the you cannot get power output to 2.0 watts or higher, see
instructions that follow we’ll assume that you’re using the K2’s Troubleshooting
built-in digital wattmeter, which will also provide satisfactory .
results.
Set the POWER control for 2.0 watts.
Switch to the 40 meter band and set the VFO for about 7100
kHz.
Locate the 40-meter band-pass filter inductors, L1 and L2, and
be prepared to adjust them using the wide end of the tuning tool.
i In the following steps you’ll place the K2 into "TUNE"
mode by holding TUNE. You should limit key-down periods to
about
5 or 10 seconds during tune-up for safety reasons. If you see or
smell smoke turn the K2 off and refer to Troubleshooting.
Note: While in tune mode, it is normal to see power drift upward
several tenths of a watt. You may also see a sudden jump in
power
during alignment. The output will quickly be reduced to about
2.0 W
by the firmware if this happens.
Put the K2 into tune mode and activate the built-in wattmeter by
holding TUNE. Using the alignment tool, adjust L1 for
maximum output.
Tap any switch to exit TUNE mode.
Enter tune mode again and adjust L2 for maximum output.
8