ELECRAFT KAT2 Notes

Notes on setting up the FWD/REF Power
settings on the KAT2 ATU
When doing the Reflected Power null adjustment on C55, you may find it difficult to determine
when you reach the null of the trimmer cap by relying solely on the K2's Front Panel LCD
display. Even at low settings of the Power control, it is common to get a Hi reading on the
display when first adjusting C55. Preset C55 to its mid position, with the screwdriver slot
parallel to the wide portion of the KAT2 Control Board.
First be sure you have the proper 50 dummy load connected to the ANT1 connector of the
KAT2, and that ANT1 is the selected antenna jack on the rear of the K2's top cover when the
KAT2 is installed. See page 16 of the KAT2 manual. Set the K2 for the 40m band.
Be sure the Power setting is set for low output, below 1 watt to start with. Since it is easy to
miss a dip in the null of C55 when a digital display of the Reflected power is used, you may find
it easier to connect an analog voltmeter to the ungrounded side of trimmer pot R2 on the KAT2
Control PCB. This is the terminal of pot R2 nearest to C55. Set the analog meter to read about 3-
5 volts full scale, and press the Tune button on the K2. Slowly adjust C55 with an insulated tool
for a dip in the meter reading. Once you get close to the null, you may see the digital display on
the K2's Front Panel indicate a small value of Reflected power. Gently turn C55 until you obtain
the lowest reading on the LCD. It should be zero, or very close to zero.
You may then want to increase the K2's Power control to 5 watts or so, to verify you have
achieved a good null. Making the preliminary adjustment at a lower power level may make it
easier to get close to the null setting, and then the final adjustment to C55 can be done at 5
watts.
WARNING:
DO NOT SET THE K2's POWER CONTROL TO MAXIMUM UNTIL YOU ARE SUCCESSFUL IN
ACHIEVING A NULL IN THE SWR SENSOR!
It is possible to damage the contacts of the latching relays in either the K2's low-pass filter, or
one of the relays in the KAT2 if there is a short circuit from the RF path to ground. High RF
currents can damage the relay contacts if there is a short circuit. Heed this warning to prevent
costly relay damage and subsequent replacement of a failed relay.
If this procedure does not work, and you cannot get a null on C55, then check the SWR sensor
T1, and all of the components in that portion of the schematic. Be sure you have a good 50 ohm