72 ELECRAFT
40-Meter Transmitter Alignment
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To align the transmitter you’ll need some means for
monitoring power output as you adjust the band-pass filters. An
analog wattmeter or oscilloscope is ideal. However, in the
instructions that follow we’ll assume that you’re using the K2’s
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.
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In the following steps you’ll place the K2 into "TUNE"
mode by holding
T U N E . 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
T U N E . 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.
Tap any switch to exit.
If necessary, repeat the adjustment of L1 and L2 two or three
times to be sure that you have the inductors peaked correctly. If
you cannot get power output to 2.0 watts or higher, see
Troubleshooting.
Make sure the bar graph is set for D O T mode using the
G R P H menu entry.
Set power output to 5.0 W using the POWER control.
Tap D I S P L A Y to enter voltage/current display mode. When
this display is selected, you can use
T U N E to check your voltage and
current in transmit mode.
Enter tune mode and note the change in voltage and current.
Current drain at 5 watts is typically 1.3 to 1.6 amps.
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If the
current reading is much higher than this, or if the voltage drops
more than 1 V, you may have a problem in the transmitter, load, or
power supply (see Troubleshooting).
Return to frequency display using the D I S P L A Y switch.
Set the POWER control for 10.0 watts.
Enter tune mode just long enough to verify that the wattmeter
reads approximately 10 watts. If you then switch to voltage/current
display and hold
T U N E again, you should see a current drain of
typically 1.8 to 2 amps. If you see a "HI CUR" warning message
(high current), use CAL CUR to set your transmit current limit
higher. If current is much higher than 2 A, see Troubleshooting.
This completes transmitter alignment and test on 40 meters.
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The K2 transmitter is most efficient at 10 watts and higher; current drain at
5 watts CW may be higher than expected. This is unavoidable because the K2
is capable of up to 15 W output. Also, for a given power level, SSB
transmission requires more transmitter "overhead" to prevent distortion.
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