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E
LECRAFT
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 ATU 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
Network Type
Tuning time
SWR Display
Current Drain
Size
Weight
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.
KXAT1
AUTOMATIC ANTENNA TUNER
Assembly and Operating Instructions
L (inductance): 0-4.5 µH in 7 steps; C (capacitance): 0-140 pF in 7 steps
L-network (series L, shunt C); C switchable to transceiver or antenna side
1 to 3 seconds typical for initial tune-up; < 1/2 sec. to recall per-band settings
1.0:1 to 9.9:1
Approx. 10-30 mA during TUNE; < 1 mA at all other times
4.8" (L) x 1.0" (D) x 0.5" (H) (12.2 x 2.5 x 1.3 cm)
1 oz.
1
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Related Manuals for ELECRAFT KXAT1
Summary of Contents for ELECRAFT KXAT1
- Page 1 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.
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Page 2: Parts Inventory
E760008 MISC Socket for U1, 18 pins E620031 MISC Foot, self-adhesive (spacer between ATU/bottom cover) E700024 Parts Placement Drawings Parts placement drawings for both sides of the KXAT1 PC board can be found in Appendix F of the KX1 manual. - Page 3 Assembly A fine-point, temperature-controlled soldering iron (700-800 degrees F) is required to assemble this kit. A high-wattage iron or one with a wide tip may damage components, pads, or traces. Use a minimum amount of solder to avoid ground shorts. All parts are installed on the top side of the board except as noted (the side with the relays, toroids, and microcontroller U1).
- Page 4 Fold down C1, C2, and C3 at about a 45-degree angle, but not so far that they contact the nearby relay pins. C1 should be folded toward K1, C2 toward K4, and C3 toward K2. Solder C1-C3 and C10 from the bottom side to avoid damaging the relays. Trim the leads on the top. In the following step, the installed height of the capacitors must be no more than 5/16"...
- Page 5 Install L1 vertically on the PC board as shown by its component outline, then pull the leads taut on the bottom of the board. Trim and solder the leads of L1. When soldering, make sure that the solder binds well to the leads. If the lead appears to be an "island"...
- Page 6 Press down on the KXAT1 at both ends to ensure that P1-P3 are fully inserted into J6-J8. Then solder all pins of P1-P3.
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Page 7: Alignment And Test
Touch the (+) lead of a digital multimeter (DMM) or analog voltmeter to the small hole near the "REFL" label on the bottom of the KXAT1 board. Connect the (-) lead to one of the KX1's long standoffs. Set the voltmeter for 2 or 3 DC volts full scale. - Page 8 Using an External Antenna Tuner If you're using an external antenna tuner, bypass the KXAT1 by setting A TU to CAL. Power and SWR will still be displayed in TUNE mode. Note: The KXAT1 cannot display SWR continuously during TUNE, so an external tuner with built-in SWR bridge is recommended.
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Page 9: Antenna Considerations
(both issues are discussed below). You should test your chosen antenna system ahead of time, if possible, to be sure the KXAT1 can achieve an acceptable match. No-feedline operation: At QRP power levels, feedline is not always necessary. In many cases you can connect a wire antenna directly to the KX1 and toss it into a tree, then lay out at least one ground radial, as shown below. - Page 10 0.5 dB. However, a low SWR will protect the transmitter, and an SWR under 2:1 is recommended. The KXAT1 always tries to hit 1:1, and with most antennas it will find an SWR below 1.5:1 on most bands. If the SWR is higher than 2:1 after matching, try using a balun or reconfiguring the antenna or changing its length.
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Page 11: Troubleshooting
If the ATU shows an error message (Exx in the menu where xx is between 1 and 49), you may have a defective microcontroller (KXAT1-U1). Ex x numbers 50-99 are used for tune-up algorithm tracking, and do not indicate a problem. - Page 12 MCLR OSC2 4.0MHz Control RYCOM NOTES: 1. K1-K7 are single-coil latching relays, shown in the RESET position. Elecraft KXAT1 Antenna Tuner Rev. Date Sht. indicates component mounted on bottom of PC board. W. Burdick 1 of 1 E. Swartz 9/30/03 Elecraft •...
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