Elecraft KAT100 User Manual

Page 29

Power Calibration (R3 and R4)

Make sure the KAT100 is set up exactly as described on page 27

(Preparing the KAT100 for Alignment). The signal must be routed
backwards through the ATU, and the KAT100 control and power
cables must be disconnected.

Power Calibration Voltage Table: During power calibration, a DC
voltage will be present at pin 3 or 5 of U5 (LM358) even though the
KAT100 is not connected to a power supply. The table below shows
target voltages at U5 corresponding to 5, 10, and 20 watts output. One
of these power levels will be used in the steps below.

Power Level

Voltage at U5

5 W

1.3 V

10 W

1.8 V

20 W

2.7 V

Select one of the power levels indicated in the table above. If you

have a K2/100, 20 watts is recommened. Otherwise, use 10 watts (if
you have a 10 watt dummy load) or 5 watts. You will only need to do
calibration at one power level.

Use a DMM for power calibration (20 or 30 V DC full-scale). The

(-) lead should be connected to a the KAT100's ground jumper.

Touch the DMM's (+) lead to pin 5 of U5 (see Figure 19).

Enter tune mode by holding

TUNE

. Adjust R4 (REFL) until the

DMM reads close to the target voltage from the table. Hold

TUNE

again when finished.

Note: In high-power mode, the power shown on the LCD should
stabilize near the desired level (20 watts) after a few seconds. On a
basic K2, power may drift upwards. Repeat the adjustment if needed.

Disconnect the cables at the KAT100's RF IN and ANT1 jacks

and reverse them.

Touch the voltmeter's (+) lead to pin 3 of U5 (Figure 19).

Enter tune mode, overriding the power limit if applicable. Adjust

R3 (FWD) until the target voltage is reached. Hold

TUNE

to exit.

With power and control cables still disconnected from the

KAT100, measure the resistance from pin 5 of U5 to ground. Record
the value here: ______ k.

Multiply this amount by 1.2 (example: if the reading is 50 k,

multiplying by 1.2 yields 60 k). Your calculated value: _______ k.

Adjust R4 (REFL) until the resistance measured at pin 5 equals

your calculated value. (This step improves the accuracy of reflected
power and SWR measurements.)