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E
LECRAFT
KXAT1
AUTOMATIC ANTENNA TUNER
Assembly and Operating Instructions
Revision B, July 27, 2011. Copyright © 2011, Elecraft; All Rights Reserved
Introduction
The KXAT1 internal automatic antenna tuner (ATU) allows random-length, end-fed wire antennas to be
connected directly to the Elecraft KX1 transceiver and used on one or more bands. It can be also be used
with most coax-fed antennas, or with balanced feedlines via a balun. Like our KAT1, KAT2, and KAT100
auto-tuners, the KXAT1 functions on receive as well as transmit. This provides an increase in receive
sensitivity and improves rejection of out-of-band signals.
The KXAT1 uses latching relays to reduce current drain to nearly zero except when tuning. These relays
select appropriate combinations of inductance and capacitance, as well as either a capacitor-in or capacitor-
out L-network configuration. Tune-up is controlled by the KXAT1's microprocessor, which also supplies
SWR and power information to be displayed on the KX1's 3-digit LED display. Once a match has been
found, matching parameters are saved so that the settings can be recalled immediately on any band change.
ATU parameters (L, C, SWR, etc.) can be viewed using the KX1’s
A T U
menu entry. Additional settings
are provided to perform component-level troubleshooting of all relays and L-network components.
In addition to being one of the world’s smallest automatic antenna tuners, the KXAT1 is very easy to build
and install. The KXAT1 module plugs directly into the KX1’s main board with no additional wiring. Gold
plated connectors and redundant connector pins are used to provide excellent reliability for field operation.
Specifications
L/C Ranges
L (inductance): 0-4.5 µH in 7 steps; C (capacitance): 0-140 pF in 7 steps
Network Type
L-network (series L, shunt C); C switchable to transceiver or antenna side
Tuning time
1 to 3 seconds typical for initial tune-up; < 1/2 sec. to recall per-band settings
SWR Display
1.0:1 to 9.9:1
Current Drain
Approx. 10-30 mA during TUNE; < 1 mA at all other times
Size
4.8" (L) x 1.0" (D) x 0.5" (H) (12.2 x 2.5 x 1.3 cm)
Weight
1
oz.
i
Ca
ution: Some components in this kit can be damaged by static discharge. Before
handling any transistors or integrated circuits, always put on an anti-static wrist strap or
touch any grounded, unpainted metal surface.
