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E
L E C RA F T
E740024 Revision D, March 22, 2017. Copyright © 2017, Elecraft; All Rights Reserved
Introduction
The KAT1 internal automatic antenna tuner (ATU) allows nearly any random-length wire antenna to be
connected directly to the Elecraft K1 transceiver and used on one or more bands. The L-network
configuration can be used with coax-fed or end-fed wire antennas, or with balanced feedlines via a balun.
Unlike some internal auto-tuners, the KAT1 functions on receive as well as transmit. This provides an
increase in receive sensitivity and improves rejection of out-of-band signals.
The KAT1 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 KAT1's microprocessor, which also
supplies SWR or power information to be displayed on the K1's LCD. 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 K1's menu. Additional menu entries are
provided to do component-level troubleshooting all relays, inductors, and capacitors.
In addition to being one of the world's smallest automatic antenna tuners, the KAT1 is very easy to build
and install. The KAT1 module plugs directly into the K1's Filter 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
i
Caution: 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.
KAT1
A UT O M AT I C A N T E NN A T U NE R
Assembly and Operating Instructions
L: approx. 0-5 µH in 16 steps; C: approx. 0-300 pF in 32 steps
L-network (series L, shunt C); C switchable to transceiver or antenna side
1 to 8 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; < 5 mA at all other times
5.0" (L) x 1.8" (D) x 0.5" (H) (12.7 x 4.6 x 1.3 cm)
1
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Related Manuals for ELECRAFT KAT1
Summary of Contents for ELECRAFT KAT1
- Page 1 In addition to being one of the world’s smallest automatic antenna tuners, the KAT1 is very easy to build and install. The KAT1 module plugs directly into the K1’s Filter board with no additional wiring. Gold plated connectors and redundant connector pins are used to provide excellent reliability for field operation.
-
Page 2: Parts Inventory
Standoff, 3/16” dia. x 5/8”, #4 hex, RAF #1323-4-A HDWR E700048 MISC Enamel wire, #26 Thermaleze, GREEN E760004 2 ft. MISC Enamel wire, #26 Thermaleze, RED E760002 5 ft. 3” MISC Hookup wire, #24 insulated E760005 MISC KAT1 PC board E100112... - Page 3 K1 Firmware Requirements To use the KAT1 antenna tuner, you'll need K1 main processor firmware revision 109 or later. (The main processor is U1 on the Front Panel board.) To check the firmware revision, hold any switch when powering up the K1. When you release the switch, the firmware revision will be shown on the LCD.
- Page 4 Install potentiometers R1 and R2 as indicated by their outlines. Make sure they are fully seated on the PC board and are not tilted. Trim the leads after soldering. This is necessary to prevent shorts when the KAT1 is installed above the Filter board. Install RF choke RFC1, which is located near U1.
- Page 5 In the following steps, inductors L1 through L4 will be wound and installed. There is no need to adjust the windings to precisely match the inductances shown on the schematic. Inductor L1 is wound on a T37-2 core (red) using 6" (15 cm) of #26 red enamel wire. To wind the inductor, pass the long end of the wire through the core exactly 8 times.
- Page 6 T1 is wound on a ferrite toroidal core (gray, FT37-43; may have an orange dot). Cut two 10" (25 cm) lengths of #26 enamel wire, one red and one green. Twist the two wires together, crossing over each other about 3 to 4 times per inch (1-2 times per cm). Then wind the twisted wires onto the core as shown below, using 10 turns.
- Page 7 Install the 3-pin male connector, P1, on the bottom of the ATU board as shown below. Before soldering, make sure the connector is seated flat against the board and is not tilted. If the connector is not mounted correctly, it may be difficult to plug the ATU board into the Filter board. Install the 10-pin, dual-row male connector, P2, on the bottom of the ATU board.
- Page 8 Unsolder the lead of R36 that is closest to the jack. Bend the resistor up and away from the board, but do not remove it completely. Note: If you need to remove the KAT1 later to align a new filter board, you will need to reconnect R36 or move the header on P3 to its original position.
- Page 9 Solder the resistor on the bottom of the board. If you plan to use the KAT1 on 80 meters, install a 100-µH RF choke on the bottom of the RF board as described in the K1B80 errata sheet. The RF choke is supplied with the 80-meter band kit.
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Page 10: Initial Test
SWR test value only, showing whether digital data is being transmitted successfully from r 8 . 5 the KAT1 to the K1 in TUNE mode. SWR Bridge Adjustment (C9) Make sure a 50-ohm dummy load is connected to the antenna jack. -
Page 11: Final Assembly
K1’s LCD shows the same power. If you’re using an RF probe: Enter TUNE mode. Once power has stabilized (about two seconds), tap until the DMM shows about 14 VDC. Then adjust R1 on the KAT1 so that the K1’s W P M + W P M - LCD shows about 5.0 watts. - Page 12 Power will be reduced to about 1.5 watts whenever SWR is displayed. Using an External Antenna Tuner (CLS and CLP) If you're using an external antenna tuner you can still use the KAT1 to display SWR or power: • Set the ATU mode to...
- Page 13 See ATU Modes for a full listing of all status displays. ATU Modes Table 1 lists all of the KAT1’s operating modes, and what is displayed when TUNE is activated in each mode. The ATU’s mode is used for normal operation. In this and all other modes where SWR is T U N displayed, power is dropped to approximately 1.5 watts during TUNE.
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Page 14: Antenna Considerations
No—this is a common misconception. For example, if the SWR is 2:1, the loss in transmitted signal strength will be only about 0.5 dB. Of course the KAT1 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 3:1, try using a balun (see below). -
Page 15: Troubleshooting
Troubleshooting If the ATU menu parameter shows "- - - " at all times, make sure you have revision 109 or later of the K1 main processor firmware. Other possibilities include a connector shifted by one position, an unsoldered pin, etc. Check the ATU PC board for shorts to ground, solder bridges, and unsoldered connections. Verify that the microcontroller is fully seated in its socket and is not plugged in backwards. - Page 16 .001 .001 NOTES: 1. R36 on the K1 RF board must be removed when the ATU is installed (see text). Elecraft KAT1 Antenna Tuner 2. K1-K10 are single-coil latching relays, shown in the RESET position. W. Burdick Rev . Date Sht.
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