Elecraft KAT2 User Manual

Page 17

Set up your DMM to read DC volts (20 or 30 volt scale).

On the bottom of the KAT2 control board, locate a pad labeled "B". Just to the left of this pad you'll

see the round pad for pin 1 of U4 (LM358). (You'll know you have the right round pad if it's part of a group
of 8 pads, 7 of which are square.) Touch your DMM's (+) probe to this pad. Connect your DMM's (-) probe
to any ground point on the K2.

In receive mode, the voltage at this test point must be 0 volts. If not, trace backwards through the

circuit to find where the voltage is coming from.

Go into TUNE mode briefly. At 5 watts, the voltage should be between 3 and 4 volts. If it is much

lower or higher than this, you probably have a wiring error in the SWR bridge. Remove the KAT2 control
board from the L-C board and check the wiring of T1. Make sure T1's leads are properly stripped.

Once you have the correct voltage indicated at U4 pin 1 in TUNE mode, install the 47-ohm resistor at

R6 (yellow-violet black). The two pads for R6 can be found looking at the bottom of the KAT2 control
board. First, locate a pad at one end of the board labeled "6V". The pads for R6 are above and below the
"6V" label. R6 can be installed on either side of the board (the component outline is located on the top, the
side with the microprocessor, etc.).

Power Calibration (R1 and R2)

Connect a known accurate wattmeter between the ATU's Ant. 1 jack and a 50-Ω dummy load. Use

short, low-loss coax cables. (An alternative to using an external wattmeter is to use an RF probe and DMM
connected to the dummy load. The reading shown on the DMM's DC volts display can be converted to
power using the formula P = V* V/ R, where R = 50. Example: 15.8 V on the DMM = about 5 watts.)

Select the 40 meter band (7000-7300 kHz). Set the K2's POWER control for 5.0 watts.

Tap the

AN T 1 / 2

button if necessary to make sure that the ANT 2 annunciator is OFF.

Using the menu, change the ATU mode to CALP (calibrate power). Exit the menu.

Note: The ATU's power display shows both forward (F) and reflected (r) power, e.g. 5.0F 0.0r
(5.0 watts forward, 0.0 watts reflected). After calibration, accuracy will typically be +/- 0.5 watts.

Locate a small flat-blade screwdriver and prepare to adjust R1 on the ATU module. Hold in the

T U N E

button and release it when you see power displayed. Adjust R1 for a power indication that matches

the reading of the external wattmeter. Hold

T U N E

again to return to receive mode.

Repeat the previous step as needed until the ATU reads the same as the external wattmeter.

Set R2 to exactly the same position as R1 (visually). This will provide adequate reflected-power

reading accuracy. You can position R2 more accurately by measuring the resistance from the wiper (center
terminal) to ground. Rotate R2 until its wiper-to-ground resistance closely matches that of R1.

Using the menu, change the ATU mode to CALS (calibrate SWR). Exit the menu. Verify that the

SWR is about 1:1 on each band using

T U N E

. Make sure that ANT 1 is selected on each band. Due to stray

capacitance, the SWR may not be exactly 1.0:1 on the highest bands; this will not affect performance.