ELECRAFT KPA1500 User manual

ELECRAFTKPA1500
1500-WATT AMPLIFIER
OWNER’S MANUAL
Revision A7, February 12, 2018
E740301
Copyright © 2018, Elecraft, Inc.
All Rights Reserved

2
Introduction
On behalf of our entire design team, we’d like to thank you for choosing the Elecraft KPA1500 amplifier.
The KPA1500 offers a unique combination of features. It’s one of the smallest 1500-W amplifiers available. The
power supply is in a separate enclosure for ease of station layout.
The KPA1500 is capable of fully automatic operation, yet has an alphanumeric display and a full complement of
front panel switches for precise manual control. A comprehensive remote-control command set is also included.
The KPA1500 can be used with nearly any transceiver, thanks to its instantaneous RF-based band switching,
advanced protection circuitry, adjustable ALC, and extensive parametric monitoring. It also has inputs that
allow direct band switching from many popular transceivers. T/R is completely noise-free thanks to the use of
PIN-diode switching.
The KPA1500 comes with a built-in Automatic Antenna Tuner (ATU) that can handle a load SWR up to 3:1 at
the full 1500 watt output in any mode.
Of course the KPA1500 is an ideal companion for the Elecraft K3Sand K3 transceivers, both physically and
electrically. The Elecraft K3Sor K3 can sense whether the amp is in standby or operate mode, then select the
appropriate per-band power settings. This allows you to set up the K3Sor K3 for “barefoot” operation at one
power level on each band, and then switch the amp to operate and set up optimal drive levels for full 1500-W
output. The K3/KPA1500 combination is also capable of extremely fast break-in, especially when the K3Sor
K3 is placed in QRQ (high-speed CW) mode. The two are so well-integrated that you can use the per-band
switches on the amplifier to change bands at the transceiver.
If you use the KPA1500 with both the K3Sor K3 transceiver and P3 panadapter –our new “K-Line” – you’ll
enjoy a high degree of operating convenience, along with world-class performance and the power to get the job
done.
73,
Wayne, N6KR
Eric, WA6HHQ

3
Contents
Introduction...............................................................................................................................................2
FCC-Mandated Part 15 Notice for the Computer Interface Ports: ...........................................................5
In the Box .................................................................................................................................................5
Installation ................................................................................................................................................6
Positioning the KPA1500 RF Deck and Power Supply ......................................................................................7
Cabling –Power Supply......................................................................................................................................8
Cabling –RF Deck..............................................................................................................................................8
Operation ................................................................................................................................................13
RF Deck Front Panel Controls ..........................................................................................................................13
Power On...........................................................................................................................................................14
Band Switching.................................................................................................................................................14
Antenna Selection .............................................................................................................................................15
Transmitting......................................................................................................................................................15
Using ALC ........................................................................................................................................................16
Automatic Antenna Tuner (ATU).....................................................................................................................17
Monitoring.........................................................................................................................................................18
Remote Operation .............................................................................................................................................19
Fault Conditions................................................................................................................................................20
KPA1500 Utility Program......................................................................................................................26
KPA1500 Firmware Updates............................................................................................................................26
Checking your Firmware Revision ...................................................................................................................26
Forcing a Firmware Load..................................................................................................................................26
Wattmeter Calibration Procedure...........................................................................................................27
Specifications..........................................................................................................................................28
Customer Service and Support ...............................................................................................................29
Theory of Operation ...............................................................................................................................30
AUX and XCVR Serial Connector Interfaces........................................................................................32
KPA1500 AUX Connector Pinout (DE-15 Male).............................................................................................32
Elecraft KPAK3AUX Interface Cable..............................................................................................................33
Icom Cable ........................................................................................................................................................33
XCVR Serial Cable...........................................................................................................................................34
TUNE Cable......................................................................................................................................................35
Yaesu Cable ......................................................................................................................................................35
BCD Interface.........................................................................................................................................36
Elecraft manuals with color images may be downloaded from www.elecraft.com.

4
WARNING
Dangerous Voltages are Present Inside the KPA1500 and its
Power Supply
Do not turn on or operate the amplifier or power supply with
the covers off.
Before opening the KPA1500 RF Deck or Power Supply
enclosures:
1. Turn off the KPA1500 by tapping the front panel ON
switch and wait until the fan stops. (The fan drains
the power supply to a safe voltage.)
2. Turn off the power supply breaker switch (on the rear
panel).
3. Disconnect the two Power Supply cables at RF Deck
rear panel before opening the RF Deck enclosure.
4. Disconnect the Power Supply from the mains before
opening the cover.
Key to Symbols Abbreviations and Text Styles
Important –read carefully
Operating tip
TEMP
Tap switch function (labeled above a switch; press for less than 1/2 second)
PK HOLD
Hold switch function (labeled below a switch; press for at least1/2 sec. to
activate)
INHIBIT
Typical text appearing on the LCD.
LED
Light Emitting Diode
LCD
Liquid Crystal Display
CAUTION
Follow the instructions under a Caution to avoid damage to the equipment.
WARNING
Follow the instructions under a Warning to avoid serious personal injury.

5
FCC-Mandated Part 15 Notice for the Computer Interface Ports:
This equipment has been tested and found to comply with the limits for a Class B digital device, pursuant to part
15 of the FCC Rules. These limits are designed to provide reasonable protection against harmful interference in
a residential installation. This equipment generates, uses and can radiate radio frequency energy and, if not
installed and used in accordance with the instructions, may cause harmful interference to radio communications.
However there is no guarantee that interference will not occur in a particular installation. If this equipment does
cause harmful to radio or television reception, which can be determined by turning the equipment off and on, the
user is encouraged to try to correct the interference by one or more of the following measures:
•Reorient or relocate the receiving antenna.
•Increase the separation between the equipment and receiver.
•Connect the equipment to an outlet on a different circuit from that to which the receiver is connected.
•Consult the dealer or an experienced radio/TV technician for help.
Regarding the computer interface: changes or modifications not expressly approved by Elecraft could void the
user’s authority to operate the equipment.
Elecraft Inc.
125 Westridge Dr.
Watsonville, CA 95076
[phone]
www.elecraft.com
In the Box
Included
ITEM
ELECRAFT PART NUMBER
RF Deck
E850767
Power Supply with AC Line Cable
E850766
DC Power Cable
E770024
DA-15 “Umbilical” Cable
E770017
Phono-Phono Key Line Cable
E100416
USB A-B Cable
E980299
Owner’s Manual
E740301
Optional
ITEM
ELECRAFT PART NUMBER
KPAK3AUX Cable set for K3s or K3
KPAK3AUX
KXUSB Serial Cable for KX2 or KX3
KXUSB

6
Installation
Installation consists of the following:
•Positioning the KPA1500 RF Deck and Power Supply to provide for proper cooling (page 7).
•Connecting the KPA1500 RF Deck and Power Supply (page 7)
•Cabling the KPA1500 RF Deck to your other station equipment (page 8).
The KPA1500 RF deck rear panel is shown in Figure 1. The connectors and controls are described following the
figure.
Figure 1. KPA1500 RF Deck Rear Panel
and SO-239 RF connectors to antenna system or dummy load.
SO-239 connector for RF input from the driving transceiver.
Low level KPA1500 transmit signal output.
Station ground attachment.
High voltage connection to the KPA1500 power supply.
Control circuit connection to the KPA1500 power supply.
Accepts a 12V input for remote control applications to power the KPA1500 on or off.
Negative-going voltage for transceivers that require ALC. (Elecraft transceivers do not require this
connection.
Key Line: enables the KPA1500 by a short to ground. When grounded the source must sink 5 mA. 5 Vdc
open circuit inhibits the KPA1500.
For interconnecting cable to fully integrate the KPA1500 with an Elecraft K3 or K3Sfor enhanced mode
operation.
Input signal to the internal KPA1500 automatic antenna tuner (ATU) that emulates an Icom remote ATU
when the KPA1500 is used with Icom transceivers.
Serial Control: Selectable Cl-V for Icom radios or RS232 level information for transceivers such as the K2,
KX2, KX3, some Kenwood and Yaesu transceivers. Radio type is selected in the menu.
Ethernet connection for local or remote operation applications.
USB connection to virtual COM port for use with the KPA1500 Utility and other computer-based programs.

7
The KPA1500 Power Supply Deck is shown in Figure 2.The connectors and controls are described below the
figure.
Figure 2. Power Supply Rear Panel.
Control: DA-15 cable with control and low voltage supplies to the RF deck.
HV Supply: Main DC power output for the RF deck
Ground: Connection to the station ground.
AC Power Cable: Supplied with a NEMA 6-20 molded plug. If needed, replace it with a suitable 20A
connector for your installation.
Power ON Switch and Circuit Breaker: Must be in the ON position for the RF deck power switch to
function.
Positioning the KPA1500 RF Deck and Power Supply
Provide at least 4 inches (10 cm) clearance behind the RF deck fans and above the Power Supply top cover.
Allow at least 1 inch (2.5 cm) clearance around the top and sides if the RF deck and around the sides of the
Power Supply for normal cooling air flow.
The supplied cables allow the power supply and RF deck to be placed up to 66 inches (167 cm) apart. The
Power Supply can be operated remotely and so need not be positioned within reach of the operator. The fans
operate whenever the KPA1500 is on, so you can place the power supply under the operating desk or elsewhere
to minimize the sound of the fans.

8
Cabling –Power Supply
Be sure the POWER ON switch ( . Figure 2) is off before connecting any cables to the Power Supply or RF
deck.
An AC power cable with the popular NEMA 6-20 connector is supplied attached to the Power Supply, The
NEMA 6-20 connector is compatible with NEMA 6-20R receptacles. Replace the connector if you need a
different connection to your mains supply
Connect the Power Supply to the RF deck with the supplied 66-inch (167 cm) cable that has an Anderson
PowerPole® connector and a 15-pin connector at each end. Plug the PowerPole connector into the HV Supply
connector ( ) on the RF Deck rear panel (see Figure 1) and the corresponding connector on the Power Supply
( , Figure 2). Observe the polarity; match the colors on the plug with the connectors. Note that the 75A
PowerPole connectors click twice when inserted. There is no electrical connection until the second “click”.
Connect the 15-pin connector to the Power Supply and the Control connector ( , Figure 1) on the RF Deck rear
panel.
Cabling –RF Deck
Always turn the KPA1500 off via the circuit breaker on the power supply before attaching
or removing cables.
The KPA1500 may be used with the Elecraft K3S, K3, K2 or any HF/6 meter transmitter and that has a keying
output meeting the requirements shown under note 4 below. Interconnections with the transceiver are shown in
Figure 3. The driving transceiver must provide at least 50 watts of RF drive for full output and the output power
must be adjustable as described under Transmitting on page 15.
Enhanced Mode Operation with a K3 or K3S
The optional KPAK3AUX cable provides closer integration with a K3 or K3S by sharing band information
between the KPA1500 and the transceiver. (see Figure 4, page 11). The KPAK3AUX cable provides all the
operational features described under Operation (page 13), including coordinated band-switching (page 14). Note
that the KPAK3AUX cable also incorporates the KEY IN line. If you need access to this line so that other
equipment can bypass the amplifier, you can install the Key Line Interrupter supplied with your KPAK3AUX
cable and use a separate key line as shown in Figure 5 on page 12.
You must use the Key Line Interrupter when using a separate key line with the
KPAK3AUX cable set. Otherwise any external equipment inserted into the key line will not
be able to inhibit the amplifier. You can make cables for use with Yaesu and Icom transceivers
that also provide closer integration with the KPA1500. For details of those cables and the
KPAK3AUX cable set see AUX and XCVR Serial Connector Interfaces on page 32.

9
IMPORTANT
1. Connect your station ground to the GND wing-nut (see Figure 1 on page 6). A good station ground is
important for safety and to minimize local radio frequency interference (RFI).
2. Attach the RF INPUT to the output of your driving transceiver or transmitter using a 50 ohm coaxial
cable with a PL-259 male connector on the KPA1500 end.
3. Attach the ANT 1 or ANT 2 connector to a suitable load with an SWR of less than 1.5:1. A 50Ω
1500W dummy load is strongly recommended for initial testing. Be sure to select the correct ANT
connector using the front panel ANTENNA switch before transmitting.
4. The driving transmitter must ground the KEY IN line circuit during transmit while sinking up to 5 mA.
This is compatible with virtually all amateur transmitters and no key line buffer is required. If the
transmitter Key Output is not a contact closure or equivalent, it must be at a level between +4 and +16
VDC during receive.

10
Figure 3. Basic Cabling Diagram for Any Transceiver.

11
Figure 4. K3SEnhanced Cabling Using KPAK3AUX Cable.

12
Figure 5. K3SEnhanced Cabling Using KPAK3AUX Cable and Separate Key Line.

13
Operation
RF Deck Front Panel Controls
Figure 6. KPA1500 RF Deck Front Panel Controls and Indicators.
The front panel controls and indicators are referred to in the following operating instructions by
the numbers shown in Figure 6. Below is a brief summary of the function of each control and
indicator.
Switches with a legend above and below the pushbutton have two functions. Tap
(press briefly) to activate the function labeled above a switch. Hold to activate the
function labeled below the switch. In the text, tap functions are shown like this:
MENU. An example of a hold function is EDIT.
Band select switches: Tap to manually select a new band at the KPA1500 (see page 14)
Menu/Edit switch: Tap to display the KPA1500 menu. Hold to edit a menu parameter.
Status switch: Tap to display Status pages showing amplifier operating parameters (see page 19).
Liquid Crystal Display (LCD).
/Up/Down Switches: Press to scroll through the Status or Menu screens.
Power Output wattmeter bargraph.
SWR bargraph.
TX LED. Lights whenever the amplifier is in operate mode and the KEY in is pulled low (enabled).
ON pushbutton switch; Toggles the amplifier power on or off.
ATU TUNE/ATU MODE switch: Tap to initiate a tune operation. Hold to toggle the internal ATU in
our out of the signal path.
ANTENNA/PF2 switch: Tap to toggle between the ANT1 and ANT2 outputs. Hold to select user-
programmable function 2.

14
MODE/PF1 switch: Tap to switch between operate (OPER) and standby (STBY) modes. Hold to select
user-programmable function 1.
RESET/INFO switch: Tap to reset a fault condition. Hold to display information about the last fault on
the LCD.
AUX switch: Used to force a firmware load (see page 26).
Power On
IMPORTANT
When the KPA1500 is turned off using the front-panel switch , part of the control circuitry
remains on as long as mains power is applied to the Power Supply. Keeping the control circuitry
energized allows the KPA1500 to be turned on and off remotely as well as from the front-panel switch.. If
you do not need to control the KPA1500 remotely and would prefer to save the small amount of power
required to power the control circuitry, either switch the Power Supply completely off or provide an
external mains power switch capable of handling 20A.
1. Ensure a suitable 50 ohm load is attached to the ANT 1 or ANT 2 connector on the rear panel. Tap
the front panel ANTENNA switch to select the antenna connector used. The associated LED will
be illuminated. A dummy load is recommended for initial tests.
2. Enable the power supply by placing the rocker switch on the power supply module in the On (I)
position. The power supply unit fan will turn on and run whenever the power supply is on.
3. Tap the ON switch . The LCD , ANT 1 or ANT 2 and the OPER or STBY LEDs should light. By
default the KPA1500 starts in standby mode at power on. You can change the behavior to have the
KPA1500 start in operate mode using the Menu (see Menu on page 21).
If the FAULT LED lights at any time, refer to Fault Conditions, page 20.
Band Switching
Band switching may be done automatically or manually as follows:
Automatic Band Switching via Frequency Counter: The KPA1500 measures the frequency of the RF
drive and automatically selects the proper band. The KEY IN input must be connected to the driving
transmitter to enable the KPA1500.
The automatic band selection via frequency counter function is active whenever the KEY IN
is low (transmit mode) and the transmitter is delivering RF drive to the KPA1500. The
automatic band selection function overrides band selection made by any other means to protect
the KPA1500 from damage by wrong-band operation.
Manual Band Switching: Tap any of the front-panel BAND switches to manually switch the
KPA1500 to that band.
Coordinated K3Sor K3 and KPA1500 Band Switching: When the optional AUX cable (page
7) is connected between the KPA1500 and the K3Sor K3:
•The KPA1500 will follow the band selected on a K3Sor K3 transceiver without the need
to transmit.

15
•Tapping a BAND switch on the KPA1500 will cause the K3Sor K3 to change bands
accordingly.
Band switching control in which the KPA1500 follows the transceiver band selection without
transmitting is available with other popular transceivers such as Icom and Yaesu with the
appropriate interconnection cable. See AUX and XCVR Serial Connector Interface on page 32.
However, the control is one-way. The KPA1500 cannot command the transceiver to change
bands as it does when connected to a K3Sor K3 with the optional AUX cable.
Antenna Selection
Tap ANTENNA to select the desired rear panel antenna indicated by a lighted ANT 1 or ANT 2 LED above the
switch.
You can choose which antenna output is used for each band. By default, the KPA1500 will return to that choice
when returning to that band. Also you can disable one of the antenna outputs for selected bands. See ANTENNA
ENABLE and ANTENNA PREFER entries under Menu on pg 21.
Transmitting
The POWER (W) and standing wave ratio (SWR) bargraphs are functional when the amplifier is in
standby (STBY). Fifty watts from the driving transceiver will illuminate the first POWER LED. You may
run up to 200 watts through the KPA1500 in STANDBY.
1. Be sure you have an antenna or dummy load connected to the active antenna output (see Antenna
Selection on pg 15) and your driving transceiver is on a frequency inside an Amateur band.
If you attempt to drive the KPA1500 on a frequency that is more than 100 kHz
outside of an Amateur band or in the range of 26 to 28 MHz, the KPA1500
automatically switches to standby, the red FAULT LED lights and a tone is sounded
in the speaker.
2. If you have a 50 ohm dummy load connected or an antenna that you know presents a low SWR to
the KPA1500, use the ATU MODE switch to put the ATU in bypass (BYP LED lights). If you are
not sure of the SWR of the load attached to the active antenna output, use the ATU MODE switch
to put the ATU in operate (IN LED lights).
3. Tap the MODE switch as needed so that the OPER LED lights.
4. Apply a few watts of RF drive and note that the POWER (W) bargraph illuminates to indicate
the RF output power. Normal drive levels to produce the full 1500 W output will be about 50 W,
but start with a much lower level to observe how the KPA1500 behaves. The KEY IN must be
pulled low and the KPA1500 must be in OPER mode for it to amplify. Note that the TX LED
lights when the KEY IN signal is present.
NOTE: If you apply RF drive at a frequency between 26 MHz and 28
MHz the KPA1500 automatically switches to standby (STBY) and will not
amplify.

16
5. Slowly increase the drive power and confirm that the SWR bargraph indicates less than 1.5
while the output indicated by the POWER (W) LEDs increases. For ease in reading the critical
SWR levels, the SWR LEDs are green from 1 to 1.5. The 1.5 to 2.1 SWR LEDs are yellow and
the LEDs for SWRs above 2.1 are red. If your load shows a higher SWR, be sure the ATU is
enabled (press the ATU MODE switch to light the IN LED), and then tap ATU TUNE to initiate a
tuning cycle. About 50 watts of drive may is required to produce the full 1500 watts output from
the KPA1500.
During heavy use, you may hear audible clicking sounds, particularly as amplifier
components cool after transmitting. This is normal. It does not indicate that the amplifier is
being overly stressed. The rear panel fans will turn on and increase speed as needed
automatically. If desired, you can keep the fans running at all time using the FAN SPEED
MIN menu setting (see pg 21)
6. When driving the KPA1500 with an Elecraft K3 or K3S, use the K3 or K3Sper-band power
control to set the amplifier output just below the desired peak output on each band. Do not rely on
ALC to control the power output (see Using ALC, page 16). At the K3 or K3S, set
CONFIG:POWER SET to Per Band and adjust the power level for each band. If your K3Sor K3
has firmware version 4.82 installed, see Per-Band Power Control in your K3 or K3SOwner’s
manual for further details.
If you use the AUX cable interface between the K3 or K3Sand KPA1500 (pages 11 or
12), the KPA1500 will send the operate/standby status to the K3 or K3S. You can then set
two per-band power levels at the K3 or K3S: one to drive the KPA1500 when it is in operate
mode and another for pass-through transmitting when the KPA1500 is in standby. The K3
or K3Swill automatically furnish your preset power levels as you switch the KPA1500
between operate and standby.
Using ALC
Automatic Level Control (ALC) is a useful safety mechanism, but never use ALC as the principle power
control. Doing so causes many of the unwanted transmit dynamics you often hear on the air including excessive
intermodulation distortion (IMD) and clicks. Instead, set your transmitter power output correctly as described
under Transmitting and adjust the ALC so it does not affect output power in normal operation. To do this, drive
the KPA1500 to the desired output. Adjust ALC THRESH in the menu (page 21) until power just starts to drop
and then set ALC THR above this setting so it does not affect the output power in normal operation.
Elecraft recommends using the K3Sor K3 PWR SET-PER BAND function to set proper drive levels, not ALC.
The Elecraft K3Sand K3 ALC intentionally have a slow attack and much slower decay to avoid adding more
distortion or dynamics problems than necessary. However, not all of the negative effects of ALC action can be
avoided. It is still best to set the ALC threshold and then adjust the drive to avoid ALC action in normal
operation.

17
Automatic Antenna Tuner (ATU)
The internal ATU may be used with the KPA1500 in either operate mode or standby. When the KPA1500 is in
standby mode, power from the driving transceiver is passed directly to the ATU. Press ATU MODE to select
whether the ATU is active (IN) or bypassed. The corresponding LED above the switch will light.
At lower power levels, such as using your driving transceiver ‘barefoot’ at 100 watts, the ATU will match loads
up to an SWR of 10:1 on 80 through 10 meters and 1.5:1 on 160 and 6 meters. At 1500 W the tuner will match
an SWR of at least 3:1. The ATU recalls the tune solutions based on the frequency reported by the KPA1500
frequency counter when the KEY IN line is held low. This works in both standby and operating mode.
Tap ATU TUNE to initiate an ATU tune cycle.
Manual Tune Operation
Relays in the ATU operate to search for values of inductance (L) and capacitance (C) that match the impedance
of the antenna to a value close to 50 ohms non-reactive for the KPA1500 amplifier circuits or for the driving
transceiver when the KPA1500 is in standby.
The SWR lights indicate how close the antenna impedance is matched to the transceiver. The L and C values
switched in will provide a good match for most situations, but if you feel the resultant SWR is high you can tap
TUNE again within 3 seconds to initiate a second, fine tuning process in which smaller changes in L and C
values are tried. That may result in a lower SWR.
If the SWR is 1.2 or less when a tune operation begins, the KPA1500 bypasses the matching network without
searching for a tuning solution. You can change the SWR at which the KPA1500 bypasses the matching
network without searching for a solution with the SWR BYP THRESH parameter in the Menu.
Automatic Tune Operation
You can configure the ATU to recall previous tuning solutions automatically when it detects load SWR greater
than a preset value. In the Menu, set ATU HiSWR AUTO RETUNE to ENABLED: (see page 21). Normally an
automatic tuning cycle begins when the load SWR exceeds 1.8:1. You can change this with the SWR AUTO
THRESH parameter in the Menu. You can set a different threshold for each band.
Memories
After successfully tuning, the KPA1500 stores the L and C settings or the bypass setting and the antenna output
used in memory. They will be recalled almost instantly when transmitting on that frequency later. The entire
spectrum from 1.8 through 60 MHz is divided into frequency segments and tuning information is stored for each
segment in which you have successfully completed a tune operation.
Since re-tuning to maintain a low SWR is normally required over a narrower frequency range on the lower
frequencies, the lower frequencies have narrower segments assigned as follows:
•Below 3 MHz the segments are 10 kHz wide.
•From 3 MHz through 26 MHz the segments are 20 kHz wide.
•From 26 MHz to 38 MHz the segments are 100 kHz wide.
•From 38 MHz to 60 MHz the segments are 200 kHz wide.

18
When starting a tune operation for a frequency segment that has no previously stored L and C values, the
KPA1500 first tries the settings in the nearest frequency segment that has tuning data.
Training the ATU
If you want to ensure that you are never faced with doing a tune operation while moving from one
frequency to another, you can do a tune operation at points across each band so that the KPA1500 will
memorize the L and C settings and antenna selected in advance. The KPA1500 ATU will not need to do a
full search tune operation again unless you change your antenna. Normally you won’t need to do a tune
operation in every segment shown under Memories above depending upon how “flat” your antenna SWR
remains across each band. If you transmit in a segment where there is no tuning solution stored, the ATU
logic automatically checks the solutions for adjacent segments to see if they produce an acceptable SWR.
When used with a K3 or K3S, the KPA1500 may be configured track frequency changes without transmitting,
providing virtually instantaneous amplifier and ATU setting updates as you tune across the band. See Frequency
Tracking with an Elecraft K3 or K3STransceiver below.
Frequency Tracking with an Elecraft K3 or K3STransceiver
When the KPA1500 is used with an Elecraft K3 or K3Stransceiver, the K3 or K3Scan be configured to cause
the KPA1500 and ATU to follow changes in the K3 or K3SVFO frequency during receive. (KPAK3AUX cable
is required.) The KPA1500 ATU will switch bands and change to the tuning solution for each frequency
segment as the K3 or K3SVFO frequency is tuned across the band. To use frequency tracking:
•Connect the KPA1500 and K3 or K3Susing the AUX interface cable as shown in Figure 4 (page 11) or
Figure 5 (page 12).
•Ensure that your K3 or K3Sis equipped with firmware revision 4.82 or later. See Firmware Upgrades in
your K3 or K3SOwner’s Manual for instructions about how to upgrade your firmware, if needed.
•Enable the frequency tracking function at the K3 or K3S: select CONFIG:KAT3 and then tap the 1
switch to toggle between KAT500N (no KPA1500) and KAT500Y (KPA1500 connected and frequency
tracking enabled).
Monitoring
KPA1500 operation is monitored by the LEDs , and and reported in text on the LCD.
LEDs
The SWR of the load and the output power are displayed on LED bar graphs. The intensity of the power bar
graph LEDs also increases as output power increases within a LED’s power range. The bar graphs are color-
coded: green for normal operating range, yellow for marginal levels and red for excessive levels. Excessive
levels may trigger a fault and shut the KPA1500 off (see Fault Conditions below). The FAULT LED lights if a
fault condition occurs. Also two LEDs indicate whether the amplifier is in standby (STBY) or operating (OPER)
mode.
LCD
Normally the LCD displays the band currently selected. The four switches around the LCD select other
information to be displayed on the screen and the behavior of the LEDs. Note that these switches have both tap
and hold functions (page 4). Repeat the tap or hold action to return the LCD to the band display.

19
STATUS
Tap UP or DOWN arrows to the right of the LCD (05,06) to move between the four STATUS pages. When
TECH MODE is enabled, additional status pages are available. Example displays are shown below. The actual
values will vary according to your operating conditions:
Band, PA current, temperature, forward power, SWR:
3.5MHz 50A 42C
PWR 1234W 1.7:1
Forward and reflected power:
FWD PWR: 1234W
REFL PWR: 23W
Banner:
ELECRAFT KPA1500
Banner text appears briefly on the LCD when the amplifier is switched on. You may customize this text
with the KPA1500 Utility Edit Configuration dialog to do, for example, display your call sign.
Forward power, efficiency, PA voltage, current, and temperature:
F: 983W 56%
52V 34A 23C
In this example, the DC power input to the amplifier was 52 volts times 34 amperes, or 1768 Watts. RF
power out was 983 Watts. Efficiency is Output power / DC power, 983 / 1768 or 56%.
LCD Transient Operator Notification Messages
Fault messages are displayed briefly on the LCD. When the band is changed, the LCD shows the new band for
about half a second, like “BAND 7 MHz”. When the ATU TUNE switch is pressed, “NEED TUNE PWR, Key
Exciter” is shown to tell the owner to provide RF for ATU tuning. You may tap ATU TUNE again to cancel the
full search tune request. “TUNE CANCELLED” appears briefly on the LCD. When ATU tuning finishes
normally, the LCD shows “TUNE COMPLETE” briefly.
Some menu items appear only when TECH MODE is enabled.
Remote Operation
The KPA1500 can be controlled remotely using a personal computer connected to the RJ45 Ethernet port or to
the USB port. A basic remote operating capability is built into the KPA1500 Utility program (see page 26). For
those who may wish to develop their own software, a Command Reference Manual is available on the Elecraft
web site. (www.elecraft.com).
Additionally, the rear panel REM jack allows turning on and off the KPA1500 semi-automatically. When +12V
is supplied, the amplifier will power ON. It will turn off when the 12V is removed. Less than 1mA of current is
required.

20
Fault Conditions
The FAULT indicator lights and the speaker sounds to indicate a fault condition has occurred. To avoid
unnecessarily interrupting amplification because of moderately abnormal conditions, there are two levels of
faults that may occur, attenuator faults and hard faults.
Attenuator Faults
Relatively minor faults such as excessive reflected power cause an internal 3dB attenuator to be switched into
the RF path that reduces the output to protect the KPA1500. When an attenuator fault occurs, the OVR LED
blinks and the cause is displayed on the LCD for about 1 second. The KPA1500 tests the condition at intervals
and will return to normal operation automatically after the cause of the fault is removed. The interval between
tests is set with the ATTEN REL menu (page 21). If the fault persists over time or if it is severe enough, a hard
fault will occur.
Unauthorized Frequency (INVALID) Fault
If you try to transmit on an unauthorized frequency the KPA1500 will automatically switch to standby and
INVALID will be displayed on the LCD until RF drive is removed.
Hard Faults
Hard faults are those that require switching the KPA1500 to standby to protect it, such as conditions of
extremely high reflected power or high drive power, or because a critical component such as a power supply has
failed. When a Hard Fault occurs, the cause of the fault is displayed on the LCD. When the condition has been
corrected, tap the OPER/STBY switch to return the KPA1500 to normal operation, or tap the INFO switch to
return the KPA1500 to standby mode.
LCD Display
Fault
Fault Type
NO KEY IN
30 WATTS
Protects the TR Switch if drive power is applied in operate
mode but the key line is not pulled down to enable the
KPA1500.
Temporary
switch to standby
LPF
VMON
Incorrect bias voltages at the TR switch.
Hard
NO MATCH
4.3
ATU unable to match to the load at the selected ANT
connector.
Hard
PA CURRENT
68 AMPERES
Excessive PA current drawn
Attenuator-Hard
PWR DISS
2050 WATTS
Power amplifier is dissipating excessive power. 1
Hard
PWR FOR
SWR BYPASS
4.3
Tuned Antenna SWR exceeds safe limits at selected power.
Attenuator-Hard
FWD PWR
2005 WATTS
Excessive forward power measured.
Attenuator-Hard
GAIN HIGH
RATIO 33
Ratio of Input Power to Forward Power too high.
TBD
FREQUENCY
INVALID 26123KHZ
RF from the driving transceiver not within 100 kHz of an
Amateur band or somewhere between 26 and 28 MHz
Hard
INPUT PWR
65 WATTS
Excessive power from the driving transceiver.
Hard