Elecraft KAT1 User Manual

E L E C R A F T K A T 1 A U T O M A T I C A N T E N N A T U N E R

Assembly and Operating Instructions

Revision C, Jan. 18, 2001. Copyright © 2001, 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 L: approx. 0-5 µH in 16 steps; C: approx. 0-300 pF in 32 steps
Network Type L-network (series L, shunt C); C switchable to transceiver or antenna side
Tuning time 1 to 8 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; < 5 mA at all other times
Size 5.0" (L) x 1.8" (D) x 0.5" (H) (12.7 x 4.6 x 1.3 cm)

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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.

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Parts Inventory

The table below lists all parts in the kit. The K1 Owner's manual has photographs of similar parts.

Ref. Description Part No. Qty

C1 Capacitor, 10 pF, 500 V NPO disc E530026 1
C2 Capacitor, 22 pF, 500 V NPO disc E530027 1
C3 Capacitor, 39 pF, 500 V NPO disc E530028 1
C4 Capacitor, 82 pF, 500 V NPO disc E530029 1
C5 Capacitor, 150 pF, 500 V NPO disc (“151”) E530030 1
C11, C12, C17 Capacitor, .001 µF, 25 V("102") E530001 3
C13, C14, C16,
RF-C76
C15 Capacitor, .047 µF, 25 V ("473") E530025 1
C10 Capacitor, 100 pF, 200 V, NPO disc ("101") E530034 1
C9 Ceramic trimmer, 5-30 pF E540001 1
D1, D2 Diode, 1N5711 E560004 2
D3 Diode, 1N34A E560000 1

FIL-J1 Conn., 3-pin female, 0.1” spcg., Samtec SSW-103-01-G-S E620009 2
FIL-J2 Conn., 5x2 female, 0.1” spcg., Samtec SSW-105-01-G-D E620045 2

K1-K10 DPDT latching relay E640001 10
L1-L4 Toroidal inductor, T37-2 core (RED); see text E680006 4
P1 Conn., 3-pin male, .1" spcg., Samtec MTSW-103-22-G-S-420 E620046 1
P2 Conn., 5x2 male, .1" spcg., Samtec MTSW-105-22-G-D-420 E620047 1
R1, R2 Trimmer potentiometer, 100K E520001 2
R5 Resistor, 100 ohms, 5%, 1/4-watt (brown-black-brown) E500010 1
R3 Resistor, 200 ohms, 5%, 1/4-watt (red-black-brown) E500020 1
R6 Resistor, 1 k, 5%, 1/4-watt (brown-black-red) E500013 1
RF-R39 Resistor, 1.8 k, 5%, 1/4-watt (brown-gray-red) E500004 1
R4 Resistor, 3.3 k, 5%, 1/4-watt (orange-orange-red) E500017 1
RF-R4 Resistor, 5.6 k, 5%, 1/4-watt (green-blue-red) E500007 1
RFC1 RF choke, 82 µH, miniature (gray-red-black) E690003 1
T1 Toroidal transformer, FT37-43 core (gray); see text E680003 1
U1 IC, Microcontroller, 16C72A or 16F872 E610007 1
U2 IC, Op-amp, LM358 E600010 1
Z1 Ceramic resonator w/internal capacitors, 4.0 MHz E660001 1
HDWR Socket for U1, 28 pins E620011 1
HDWR #4 split lock washer (2 spares) E700004 4
HDWR 4-40 x 1” ZN ST Phillips machine screw (2 spares) E700047 4
HDWR Standoff, 3/16” dia. x 5/8”, #4 hex, RAF #1323-4-A E700048 2
MISC Enamel wire, #26 Thermaleze, GREEN E760004 2 ft.
MISC Enamel wire, #26 Thermaleze, RED E760002 5 ft.
MISC Hookup wire, #24 insulated E760005 3”
MISC KAT1 PC board E100112 1

Capacitor, .01 µF, 25 V ("103") E530009 4

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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.

KAT1 PC Board Assembly

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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.

since removing parts from double-sided PC boards can be difficult.

component outline, but do not solder. Do not bend the relay leads. Note: The reference designators for the
relays may be difficult to read on the rev. C board. They are sequential, starting from the left with K1.

the first row. Do not solder yet.

over. Solder two diagonal corner pins on each relay.

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Install components only in the order described below. Double-check all values before soldering,

Place relays at locations K1-K5, with the white-striped end of each relay oriented as shown by its

Place relays at locations K6-K10. This second row of relays faces in the opposite direction from

Using a book or other flat object to hold the relays in place on the top side of the board, flip the board

Inspect all 10 relays closely to make sure that they’re seated flat against the PC board. If not, re-heat
the corner pins one a time while pressing down on the relay. Once all relays are properly seated, solder the
remaining pins.

Install the 28-pin IC socket at U1. The notched end of the socket must be aligned with the notched
end of the component outline.

Install the following resistors, starting with R6 in the upper left-hand corner of the board:

__ R6, 1k (brown-black-red) __ R5, 100 ohms (brown-black-brown)
__ R4, 3.3k (orange-orange-red) __ R3, 200 ohms (red-black-brown)

Install the three diodes, with the banded end of each diode oriented as shown on the board. D1 and D2
are type 1N5711. D3 is a type 1N34A, with a larger glass body. Note: On the revision C PC board, D3 may
be a tight fit. Pre-form the leads if necessary.

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.

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Install RF choke RFC1, which is located near U1.

Ceramic resonator Z1 looks like a capacitor with three leads. Install Z1 (to the left of U1). Be careful
not to overheat the resonator when soldering, as this can alter the resonant frequency. Keep soldering time
to 1-2 seconds per lead. Trim the leads after soldering.

Install the LM358 IC at U2, with the notched or dimpled end oriented as shown by the component
outline. Bend two corner pins to hold the IC in place, then solder.

Install the trimmer capacitor, C9. The flat side of C9 should be oriented to the left as indicated by its
outline.

Install the following capacitors. Note: On the rev. C PC board, the pads for C5 (150 pF) and C17
(.001 µF) may not be spaced perfectly for the supplied capacitors. You may need to pre-form the leads
before installation.

__ C1, 10 pF __ C2, 22 pF __ C3, 39 pF __ C4, 82 pF __ C5, 150 pF (151)

__ C11, __ C12, and __ C17, .001 µF (102) __ C13, and __ C14, .01 µF (103)

__ C15, .047 µF (473) __ C16, .01 µF (103) __ C10, 100 pF (101)

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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, pass the long end of the wire through the core exactly 8 times. Each pass through the core counts
as one turn. The finished winding should look like the illustration below. Exact turns spacing is not critical.

Inductor L1 is wound on a T37-2 core (red) using 6" (15 cm) of #26 red enamel wire. To wind the

Remove insulation

Spread out the turns of L1 so they occupy about 80-90% of the core’s circumference.

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Cut L1's leads to about 1/2" (12 mm) long. Completely remove the enamel insulation from the leads
to within 1/8” (3 mm) of the core. The enamel wire provided can be heat-stripped using a small amount of
solder on the tip of your iron. Stripping using this method takes 4-6 seconds.

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" in a small pool of solder, chances are it is not making good contact.
Measure from pad to pad using an ohmmeter to verify the connection.

Wind and install L2 through L4 using the same procedure you used for L1. The number of turns and
wire length for each inductor is shown below.

__ L2, 12 turns (8" [20 cm]) __ L3, 17 turns (11" [28 cm]) __ L4, 25 turns (15" [38 cm])

T1 is wound on a ferrite toroidal core (gray, FT37-43). 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. Each
pass through the core counts as one turn, and turns spacing should closely resemble the illustration.

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The wires labeled (1) and (3) should originate from below the core, and wires (2) and (4)

from above it, as shown below. This will ensure that the transformer has the correct phasing.

4 (RED)

2 (GRN)

1 (GRN)

3 (RED)

Trim the leads of T1 to about 1/2" (12 mm) long. Completely remove the insulation from T1's leads
up to the edge of the core, using a solder pot or hot soldering iron tip. Do not attempt to burn off the
insulation using a match or lighter, as the flame may fuse the pairs of wire together, causing them to
become shorted. Another way to remove the insulation is to use fine sand paper.

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