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E
LECRAFT
KAT2
AUTOMATIC ANTENNA TUNER
Assembly and Operating Instructions
Revision F, August 3, 2012. Copyright © 2012, Elecraft; All Rights Reserved
Introduction
The KAT2 internal automatic antenna tuner (ATU) allows nearly any antenna to be connected directly to
the K2 and used on most if not all bands. The L-network configuration provides a wide impedance-
matching range, and can be used directly with coax-fed or end-fed wire antennas, or with balanced
feedlines via a balun. Unlike some internal auto-tuners, the KAT2 functions on receive as well as transmit.
This provides an increase in receive sensitivity and improves rejection of out-of-band signals.
The KAT2 uses latching relays to reduce current drain to nearly zero except when actually 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 KAT2's microprocessor, which also
supplies SWR or power information to be displayed on the K2's LCD. Once a match has been found, the L,
C, and other matching network data are stored in EEPROM so that the settings can be recalled immediately
on any band change. ATU parameters (L, C, SWR, etc.) can also be viewed using the menu.
Two antenna jacks are provided on the ATU, with the matching network data for both antennas stored on a
per-band basis. Once an initial match has been obtained for both antennas on a particular band, the operator
can tap the
AN T 1 / 2
button on the front panel to switch between them. Since the relays take only a small
fraction of a second to switch, it becomes practical to quickly try both antennas anytime the distant station
is weak, an advantage during contest operation.
Specifications
L - C Ranges
L: approx. 0-20 µH in 256 steps; C: approx. 0-2400 pF in 256 steps
Network Type
L-network (series L, shunt C); C switchable to transceiver or antenna side
SWR Range Matched
Up to 10:1 typ. (varies with band; smaller range on lowest/highest bands)
Tuning time
1 to 5 seconds typical for initial tune-up; < 1/2 sec. to recall stored settings
SWR Display
1.0:1 to 9.9:1
Power Display
0-20 watts (approx.); forward and reflected power shown in 0.1-w increments
Current Drain
Approx. 10-30 mA during TUNE; < 5 mA at all other times
Size
4.2" (L) x 1.6" (D) x 1.5" (H) (10.7 x 4.0 x 3.8 cm)
