Elecraft KXPA100 Manual User Manual

Page 25

 Power Control: The KX3

PWR

control now has a range from 0 to 100 watts. The KX3 monitors the

amplifier power output through the Adapter Cable and adjusts the RF drive automatically to produce the
output power from the amplifier that you selected with the KX3

PWR

control. At low power settings,

the KX3 does not ground the Key Line so the amplifier passes the RF through without amplification. At
settings above 10 watts the KX3 automatically grounds the key line to enable the amplifier.

Each amplifier is calibrated to report the correct output power to the KX3 so the

KX3 power display is correct. However, if you have an RF power meter that you
feel is more accurate, you can adjust this calibration yourself. See Appendix B: KX3
Power Output Display Calibration on page 54 for details.

 Band Switching: The KXPA100 amplifier automatically follows band changes at the KX3 using data

passed through the KX3 to KXPA100 Adapter Cable. The amplifier also senses the frequency of the RF
from the KX3. If the band data is missing or does not agree with the frequency sensed for any reason,
the amplifier switches according to the frequency sensed.

 Monitoring: You can monitor the temperature of the KXPA100 power transistor heat sink from the

KX3. With the

PWR

control set high enough to engage the amplifier (see Power Control, above) tap

D I S P

and rotate the

OFS

knob to

PA.

followed by the temperature in Celsius. The KXPA100 self-

protection circuits will declare a fault condition and switch the amplifier into bypass if the temperature
rises too high (see Faults on page 32). The KX3’s internal power amplifier temperature can be
displayed by turning the

PWR

control below the level where the KXPA is switched in. The LCD will

now display

PA.I

followed by the temperature in Celsius.

 DC Power Control: The KXPA100 amplifier switches off automatically a few seconds after the KX3 is

turned off provided the KXPA100 front panel

OFF/ ON

switch is

OFF

To turn the KXPA100 off at the KX3:

 Hold

M E N U

 Turn the

OFS

knob to

PA MODE.



rn the VFO

knob to

OFF

The KXPA100 amplifier will switch off and can be turned on again by reversing the process

and turning the VFO

knob to

. While off, the amplifier passes signals through to the

ANT 1

connector.

The KXPA100 front panel

OFF/ ON

switch will turn the amplifier on independent of the menu

setting at the KX3 or whether the KX3 is on.

ATU Operation Using the KX3 to KXPA100 Cable

If the KXPA100 is equipped with the optional KXAT100 ATU, it is controlled from the KX3 using the same
controls normally used to control the KX3’s internal ATU. The KX3’s internal ATU was automatically
bypassed when you switched the KX3 menu to

PA MODE

in the Initial Settings, above.

Enabling PA MODE and bypassing the KX3’s internal ATU also bypasses the tunable

broadcast band (BCB) filter in the KXAT3 ATU. If you want to tune the broadcast band
using this filter, first turn PA MODE off in the KX3 Menu.