Elecraft KXPA100 Manual - Manual (Page 26)

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ATU Modes: You can select the ATU operating mode from the KX3. Hold M E N U , turn the OFS knob to ATU.x
MD and turn the VFO A knob to select the desired mode: bypass, manual, or auto. The KXPA100 front panel
LEDs will change to indicate the mode selected:
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: In this mode, the KXAT100 ATU behaves in the same way as the KX3’s
internal KXAT3 ATU option. 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.
 ATU Tuning: Tap
AT U T U N E on the KX3 to initiate a tune cycle at the amplifier. If the ATU was in
bypass mode, it will automatically switch to manual and the KX3 will supply RF drive while the ATU
performs a tune operation. The KXPA100’s
25/SWR LED under POWER OUT (W) blinks while the
tuning operation is taking place. The SWR is displayed on the KX3 LCD and on the KXPA100 front
panel LEDs. The ATU automatically stores the tuning solution in memory. If you are unhappy with the
SWR displayed after a tune operation, tap
AT U T U N E again within five 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.
 ATU Memories: The ATU has a large number of memory locations to provide storage for tuning
solutions at frequencies from 1.5 MHz to 60 MHz. (See Theory of Operation on page 38 for details of
the frequency segments.) A separate set of memory locations is provided to store tuning solutions for
each antenna connector. When you change bands, the KX3 returns to the last frequency used on that
band. If a corresponding tuning solution had been previously stored for that frequency, it is recalled
from memory so the KXAT100 is ready to transmit immediately. The tuning solution is also recalled if
you use direct frequency entry or recall a frequency from memory at the KX3. When tuning across a
band, the ATU will retrieve the tuning solution for each frequency when you transmit, assuming one
had been stored previously. The amplifier is inhibited for a fraction of a second the first time you
transmit while this occurs.
If you wish to QSY as quickly as possible to various frequencies without going through
a tune operation, you can prepare the ATU by performing a tune operation on
frequencies across each band. That will store the tuning solution so the KXPA100 will
be ready without retuning when you return to that frequency. The number of frequencies
you will need to perform a tune operation on so the SWR is acceptably low on all
frequencies depends upon the band and your antenna.