Elecraft KXPA100 Manual - Manual (Page 28)

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
Power Control: Set the FT-817 for 5 watts output for maximum output from the KXPA100. The ALC
system will control the amplifier power output to provide maximum power on each band. The
POWER
OUT (W) LEDs light to indicate the power output from the amplifier. These LEDs light in from left to
right as a bar of light. For example, 70 watts output is indicated by the LEDs under 25, 50, 60 and 70
being lit.
The output of power amplifiers typically vary ±1 dB for a given power input. For
example, the amplifier may provide anywhere between 80 and 120 watts output for 5 watts
of drive and may vary from band to band. This is typical.
ATU Operation with the FT-817 Interface Cable
 ATU Modes: The ATU modes are selected by tapping the
M O D E switch. on the KXAT100 front panel.
Bypass (Byp) Mode: The ATU matching network components are bypassed and the output of the
amplifier is routed directly to the selected antenna connector (
ANT 1 or ANT 2 ).
Manual (Man) Mode: When RF is applied the ATU first checks to determine if there is an
acceptable tuning solution in memory for that frequency. If not, a tune operation must be launched
manually. The tuning solution is stored in memory and associated with the antenna connector used,
so you can have a tuning solution in memory for
ANT 1 and a different solution for the same
frequency in ANT 2 to support a different antenna.
Automatic (Auto) Mode: When RF is applied, the ATU first checks to determine if there is a
tuning solution in memory that will result in an SWR of 1.8:1 or less. If not, the ATU
automatically begins a full search for the optimum tuning solution. The tuning solution is stored in
memory and associated with the antenna connector used, so you can have a tuning solution in
memory for
ANT 1 and a different solution for the same frequency in ANT 2 to support a different
antenna.
 Preparing to Tune: With the amplifier on, tap the
T U N E switch. The 25/SWR LED under POWER
OUT (W) will start blinking indicating that the ATU is ready to perform a tune operation. If the ATU
MODE was in Byp (bypass) it will switch automatically to Man (manual) mode. The tune operation can
be done in either
Man or Auto (automatic) mode. Tap T U N E a second time if you wish to cancel the
tune operation
 Tuning: Apply 5 watts from the FT-817 transceiver. You will hear relays click as the ATU finds the
best match and stop when it is done. The 25/SWR LED will continue blinking throughout the tuning
operation and stop when it is completed. The resulting SWR will be displayed. The SWR is displayed in
the same way as the power output. For example, if the final SWR is 1.5:1 the 1, 1.2 and 1.5 LEDs will
be lit. If you are not happy with the SWR, tap the
T U N E switch again within 5 seconds. The ATU will
do a second tune operation using smaller steps in the inductance and capacitance values. This process
takes longer, but may result in a lower SWR.