ELECRAFT KX3 Operating instructions

Elecraft® KX3
KX3-2M 2-Meter and KX3-4M 4-Meter
Transverter Options
Installation and Operating Instructions
Revision A5, September 5, 2014
Copyright © 2014, Elecraft, Inc., All Rights Reserved
Introduction ...................................................................................................................................... 2 Specifications ................................................................................................................................... 2 Setup and Operation ......................................................................................................................... 3 Configuring the KX3 for the KX3-2M or KX3-4M Module ..................................................................... 3 Antennas ..................................................................................................................................................... 3 Operation .................................................................................................................................................... 4 Frequency Stability ................................................................................................................................ 4 VHF Operating Frequencies ................................................................................................................... 4 KX3-2M/4M Tuning .............................................................................................................................. 5 FM Operation ......................................................................................................................................... 5 Basic Setup ......................................................................................................................................... 5 Repeater Operation ............................................................................................................................. 6 Sending DTMF Tones ........................................................................................................................ 9 Channel Hopping (Scanning) ............................................................................................................. 9 Monitoring the Repeater Input Frequency ......................................................................................... 9 Sleep Mode ....................................................................................................................................... 10 Troubleshooting .............................................................................................................................. 10 Circuit Description ......................................................................................................................... 11 Installing the KX3-2M or 4M Module ........................................................................................... 12 Preparing for Installation .......................................................................................................................... 12 Preventing Electrostatic Discharge Damage ........................................................................................ 12 Choosing an Anti-Static Mat ................................................................................................................ 12 Tools Required ......................................................................................................................................... 13 Parts Supplied ........................................................................................................................................... 13 KX3-2M or 4M Transverter Assembly Bag (E850580)....................................................................... 13 Adapter Board ...................................................................................................................................... 13 Hardware Bag, KX3-2M or 4M (E850635) ......................................................................................... 14 Installation Procedure ............................................................................................................................... 15 Separate the Case Halves ..................................................................................................................... 15 Install the Internal Coaxial Cables ....................................................................................................... 16 Installing the Antenna Coaxial Cable ............................................................................................... 17 Installing the Local Oscillator Coaxial Cable .................................................................................. 20 Prepare the KX3 for the KX3-2M or 4M Module ................................................................................ 23 Installing the KX3-2M or 4M Board .................................................................................................... 25 Customer Service and Support ....................................................................................................... 30 Technical Assistance ............................................................................................................................ 30 Repair / Alignment Service .................................................................................................................. 30 1
Introduction
The KX3-2M or 4M transverter extends the frequency range of the KX3 to include the 2 meter or 4 meter
Amateur bands and allows reception on frequencies near those bands. Either the 2-meter or the 4-meter
transverter may be installed. The transverter plugs into existing connectors inside the KX3. All KX3
functions and modes are available when using either transverter. The KX3-2M or KX3-4M transverter uses
a separate antenna connector that bypasses the KXAT3.
CAUTION
The KX3-2M or KX3-4M module and many components inside your KX3 may
be damaged by Electrostatic Discharge (ESD) simply by touching them or a
circuit board containing them unless you take specific steps to prevent such
damage. If you are installing the KX3-2M or KX3-4M module yourself, see
Preventing Electrostatic Discharge Damage on page 12 before opening the
package containing the KX3-2M or KX3-4M module or working inside your
KX3.
Specifications
General
Transmit Frequency Range:
KX3-2M: 144 MHz – 148 MHz
KX3-4M: 69.9 MHz – 70.6 MHz (covers all known 4-meter
frequency allocations)
Receive Frequency Range:
Power Consumption:
KX3-2M: 120 MHz – 150 MHz, typical, with reduced
sensitivity outside of 144-148 MHz
KX3-4M: 65 MHz – 72 MHz, typical, with reduced sensitivity
outside of 69.9-71 MHz.
120 mA receive, squelch open, typical, in addition to the
normal KX3 current demand whenever the 2 meter or 4 meter
band is selected.
Sleep Mode (see page 10) can reduce the overall radio
current to about 150-180 mA in FM Mode (squelched).
1.7 A at 3W output, total radio current, typical for the KX3
when transmitting on 2M or 4M.
Receiver, 2M and 4M
Sensitivity:
MDS -144 dBm, typical, at 500 Hz bandwidth.
Transmitter, 2M and 4M
Output Power:
2.5 W Minimum with 13.8 Vdc supply (2.5 to 3 watts typical)
2 W Maximum with 11 Vdc supply
1.5 W Maximum with 9 Vdc supply
2
Setup and Operation
If you haven’t already done so, follow the instructions starting on page 12 to install the KX3-2M or KX34M module.
Before you can use the KX3-2M or KX3-4M module, you must configure the KX3 as follows.
Configuring the KX3 for the KX3-2M or KX3-4M Module

Attach power to the KX3 and tap B AN D – and AT U T U N E switches simultaneously to turn it on.

With the KX3 on, hold the M E N U switch to enter the menu.

Turn the VFO knob to FW REVS . The LCD will display the revision of the firmware installed.
It must be uC 02.18 or later (a higher number). If not, download and install the latest firmware as
described in the KX3 Owner’s manual under Firmware Upgrades.

Turn the VFO
knob to 2M/4M MODE and turn the VFO

Turn the VFO
knob to TECH MD and turn the VFO
knob to nor.
knob if needed to On.
The remaining steps require you to unlock the VFO knob for each setting. Unlock the
VFO knob by holding K H Z until UNLOCK appears briefly in the VFO B display area. A
small padlock symbol in the upper right corner of the display will disappear when VFO is
unlocked.

Turn the VFO knob to XVn ON . n is the number of the transverter band you wish to assign to
the internal 2M or 4M module. You can assign any number from 1 to 9 by tapping the 1 through 9
switches that you have not assigned to an external transverter. The default is 1. After entering the
number turn the VFO knob to YES. In the following steps n is the transverter number you chose.

Turn the VFO knob to XV n RF and turn the VFO
70 if installing the 4 meter module.
knob to 144 if using the 2 meter module or

Turn the VFO knob to XV n IF and turn the VFO
if using the 4 meter module.
knob to 50 if using the 2 meter module or 21

Turn the VFO

Turn the VFO knob to XV n OFS and turn the VFO knob to 0.00. Offset is not used with the
internal module. If there is a frequency error, use the REF CAL procedure in your KX3 Owner’s
Manual.

Turn the VFO

Tap the M E N U switch to exit the menu.
knob to XV n PWR and turn the VFO
knob to XV n ADR and turn the VFO
knob to H 3.0.
knob to Int. trn0.
(Continued on next page)
3

Turn the KX3 power off, then on again by tapping the B AN D – and AT U T U N E switches
simultaneously for the changes to take effect.
1) Do not turn off your power supply. Always use the front panel switches to turn power
on and off. Although disconnecting your external power supply when no batteries are
installed in the KX3 will often cause no harm, certain parameter changes may not be saved
and it is possible to corrupt some data that could require you to reload the firmware.

After cycling power hold M E N U to re-enter the menu and then turn the VFO knob to BND MAP.
Tap the B AN D – and B AN D + switches as needed to display 144 for the 2 meter module or 70 for
the 4 meter module and then turn the VFO knob, if needed, to display In.

Tap the M E N U switch to exit the menu.
Antennas
Connect your 2 or 4 meter antenna to the female SMA connector mounted on the KX3’s right end plate.
Note that when you select the 2 or 4 meter bands, ANT2 appears on the LCD indicating that the SMA
connector is in use (see Figure 1 on page 5). The BNC connector is used only for the 160 through 6 meter
bands.
The antenna system must present a load very close to 50 ohms (have a low SWR) for full power output and
efficient operation. The KXAT3 Automatic Tuner option, if installed, does not function on 2 or 4 meters.
The 2 or 4 meter RF output is completely separate from the KXAT3 signal path.
Antenna polarization (vertical or horizontal) has more effect on signal strengths in the VHF range than it
does on the HF bands. Vertical polarization is normally used for FM communications to match the
polarization of mobile whips and ‘rubber duck’ antennas on hand held radios. Horizontal polarization is
most common for SSB, AM, CW and Data modes.
Operation
Complete operating information is included in your KX3 Owner’s Manual. The following is specifically to
help you get the most from your KX3-2M or KX3-4M in FM mode. Additional information about your
KX3-2M or 4M may be found in the FAQ on the Elecraft web site:
http://www.elecraft.com/manual/KX3-2M%20FAQ.htm
Frequency Stability
The standard (uncompensated) frequency stability is sufficient for FM or AM operation. For CW, SSB or
Data use, it will be necessary to perform the KX3 extended VFO temperature compensation procedure,
providing typical stability of about ± 10 Hz on 2 or 4 meters. This is compatible with 170-Hz-shift RTTY
but may not be compatible with some narrowband modes such as JT65 or WSPR. The extended
temperature compensation procedure is available on the Elecraft web site:
http://www.elecraft.com/manual/KX3%20Custom%20VFO%20TC%20rev%20A9.pdf
VHF Operating Frequencies
The VHF bands are typically organized by operating mode and type of communications, with frequencies
set aside for beacons and sub bands reserved for weak-signal work to avoid interference from local stations.
Also, frequencies are set aside for FM communications along with input-output frequency pairs for FM
repeaters to avoid interference with other modes. More information about the band plans can be found at
www.70mhz.org for 4-meter operation and www.arrl.org/band-plan for 2-meter operation.
4
KX3-2M/4M Tuning
Tap the B AN D + or the B AN D ˗ switch to select the 2 or 4 meter band, depending upon which transverter
you have installed.
As on HF, the KX3 tuning can be done using direct frequency entry or with the VFO knobs. For FM
communications you may find tuning more convenient to switch the tuning rate to 5 kHz steps: hold K H Z
to switch the tuning rate. Tap R AT E to restore finer tuning steps. This tuning rate is determined by the
VFO CRS setting in the menu. It is per-mode and can be set to a convenient value for each mode using the
menu. The default values are 5 kHz in FM mode, 500 Hz in SSB (USB or LSB), 100 Hz in CW and 1 kHz
in AM. See VFO CRS under Menu Functions in your KX3 Owner’s Manual for information about
changing the default step sizes.
To make a direct frequency entry, tap F R E Q E N T , then enter 1 to 3 MHz digits, a decimal point, and 0 to 3
kHz digits, followed by tapping . . . (Note that the 7, 8 and 9 number switches are activated by tapping
the AF / R F - S Q L , P B T I / I I , and K E Y E R / M I C encoder knobs.)
The following sections describe how to store frequencies in memory for quick QSY. For repeater operation
the PL tones and offsets are also stored so you can switch to a repeater channel and be ready to
communicate with a few simple key presses. Also you can have the KX3 scan preselected channels stored
in memory and monitor a second frequency, such as a repeater input frequency, for activity.
FM Operation
Figure 1 shows the KX3 LCD identifying only those elements mentioned in the this text. See your KX3
Owner’s manual for a complete description of the display.
Figure 1. KX3 Display.
Basic Setup
Set up your KX3 for FM operation on 2 or 4 meters as follows.

Enable FM mode as follows. This need be done only once. FM mode will remain on unless you
re-enter the menu and turn it off.
o
Hold M E N U .
o
Turn the VFO
o
Tap M E N U to exit the menu.
knob to FM MODE and turn the VFO
5
knob to On.

Select FM mode: Tap M O D E until FM appears on the right hand edge of the LCD.

Set Voice Monitor Level: If you wish to monitor your voice in the phones or speaker while
transmitting, hold M O N to switch the VFO B display to MON and then turn the knob to set the
level of the audio between 1 and 30. High levels may result in distortion or feedback. Suggest you
start with MON 5 or less as shown on the LCD. MON 0 turns the monitor function off.

Set Display to CMP/ALC: If the bargraph indicates SWR/RF tap the
switch the display to CMP/ALC.
KEYER/MIC control to
Be sure you have a suitable antenna or dummy load connected to the SMA antenna
connector when making the following transmitter adjustments.

Set Microphone Gain Level: Press the microphone PTT switch and, while speaking normally into
the microphone, adjust the
KEYER/MIC control for 5 or 6 bars indicated on the LCD ALC
display as shown in Figure 1.

Set RF Power Output Level: Exit transmit mode, and hold P W R . The output power setting
will be displayed in the VFO B area of the LCD. Adjust the knob for the desired output power, and
then tap the knob to exit the power adjustment.

Frequency Deviation: The KX3 is programmed with commonly used values of FM frequency
deviation (3.5 kHz for voice and 0.36 kHz for PL tone used by repeaters). If different values are
used in your area, hold M E N U and use the VFO knob to locate FM DEV on the LCD. This
setting is locked to avoid accidental changes. Unlock the control by holding K H Z for several
seconds until the padlock symbol to the right of the deviation value shown on the LCD disappears,
and then set the desired deviation with the VFO knob. If needed, display and change the PL tone
by tapping the 1 switch, and then unlock and change the PL deviation in the same manner. Tap
M E N U to exit the menu.
Do not attempt to increase your “talk power” by increasing the deviation. Optimum
results require that your deviation match the deviation used by the other station. See
Troubleshooting on page 10 for more information.

Simplex or Repeater Operation: Setting up your KX3-2M/4M for repeater operation is described
below. For Simplex operation, hold AL T repeatedly as needed to display SIMPLEX in the VFO B
area of the LCD.
Repeater Operation
Repeater operation requires transmitting on the repeater’s input frequency and receiving on the repeater’s
output frequency. Also, many repeaters require a sub-audible tone transmitted with the voice audio or a
short burst of tone at 1750 Hz to activate the repeater transmitter. The KX3 can be programmed with the
required transmit and receive frequency pairs and tones, selected from a list of standard tone frequencies, to
make setting up for any repeater or simplex channel a simple matter of recalling a memory location.
Frequency Memory Editor
Although you can enter all the necessary information using just the KX3 front panel controls (see Manual
Frequency Entry on page 7), the easiest way to program your KX3 for repeater operation is to use the K3
Frequency Editor program available from the Elecraft web site at:
http://www.elecraft.com/K3/FreqMemEdit/K3_Freq_Mem_Editor.htm
Note that the editor refers to the Elecraft K3 transceiver throughout. The same
editor is used with the KX3.
6
To use the editor, connect your computer to the KX3 using the same serial cable you use with the KX3
Utility Program and select the active comm. port.
The editor uses a simple spreadsheet format. Figure 2 shows a typical frequency editor screen with 2-meter
FM repeater entries.
Figure 2. Frequency Editor Screen.
Initially the Offset and PL Tone columns will not be displayed. They will appear when you select FM as
the mode for any entry

ID column: The memory location number. The number will be displayed on the KX3 LCD when
the memory is recalled. Up to 100 frequencies can be entered (00-99).

Label: User selected up to 4 characters long. The asterisk (*) has special significance for scanning
the channels entered to check for activity. See Channel Hopping (Scanning) on page 9 for details.

Description: You can enter up 23 characters to identify the use of the frequency. This data is not
displayed at the KX3.

QSY: Clicking the radio button while the KX3 is connected to the computer switches to KX3 to the
band and frequency shown. Also, you can switch to any memory at the KX3 without using the
computer. Hold R C L to display the frequency memories in the VFO B area of the LCD. Turn the
VFO knob to step through the memory locations. The KX3 will shift to each frequency as each
memory location is selected.

VFO A: The repeater output frequency (KX3 receive frequency).

Mode: Select FM for the Mode A and B columns.

Offset: The offset is the difference between the repeater input and output frequencies. Choose the
offset from the drop-down list. Be sure to choose the right sign. The offset is positive (+) if the
repeater output frequency is above the input frequency and negative (-) if the repeater output
frequency is below the input frequency.

PL Tone: If required, choose the PL tone frequency from the drop down list for each repeater.
Click on Send All to K3 when finished to store the data in the KX3 memories. Note that buttons are
provided on the editor tool bar for reading existing memory information from the KX3 and for erasing
memories, as a group or individually.
Non-repeater entries are made in the same way but without showing an offset, just as you can enter
frequencies for any other band or mode covered by the KX3.
Manual Frequency Entry
You can set up the KX3-2M or 4M for repeater or simplex operation and store the information in the
KX3’s memory without a computer as follows:

Select FM mode: tap M O D E as needed so FM appears on the right end of the LCD.
7

Enter the KX3 transmit frequency using the VFO knob or with direct frequency entry. For
operation with a repeater this will be the repeater input frequency.

For operation with a repeater, select the correct offset (difference between repeater input and output
frequencies), offset direction (repeater input frequency above or below the output frequency) and
the PL tone frequency (if needed) as follows:
o
The default offset is 600 kHz. You can check the value and change it as needed: hold
M E N U and select RPT OFS with the VFO
knob, and then use the VFO knob to select
the correct offset value displayed in kHz. Tap M E N U to exit.
o
Hold AL T repeatedly as often as needed until TX + X.XX appears on the LCD VFO B area
if the repeater input frequency (KX3-2M or 4M transmit frequency) is higher than the
repeater output frequency or until TX – X.XX appears if the repeater input frequency is
lower than the repeater output frequency. The X.XX is the offset (difference between
repeater input and output frequencies) that you entered above. The + or – sign, indicating
the direction of the repeater offset, will appear below FM on the LCD.
Be sure you select the correct sign ( + or – ) that corresponds to the direction of
the repeater offset. If you selected the wrong sign, you can change it by holding
REV.
o
If the repeater requires a PL tone, hold P I T C H . The VFO B area of the LCD will show PL
OFF or PL X.XX, where X.XX is the PL tone frequency. This is a toggle that alternates
between tone off and tone on. To change the PL tone frequency, turn the KEYER/MIC knob
to step through the standard tone frequencies. Tap M E N U to exit. Selecting the 1750 Hz PL
tone frequency adds a 0.5 second tone burst to the beginning of each transmission (for
European repeaters). Holding P I T C H while transmitting extends the tone indefinitely.

Hold S T O R E and then use the VFO knob to locate the desired memory location shown in the
VFO B area of the LCD. Hold S T O R E again or tap any switch to cancel. To recall previouslysaved data, hold R C L (recall) and use the VFO knob to select the desired memory location. Tap
any switch to exit.

If desired, add labels to each memory location or edit an existing label as follows:
o
Hold R C L (recall) and use the VFO
o
Turn the VFO knob. A cursor will appear to the right of the memory number on the
LCD. If no label has been stored before, a series of dashes indicating the 5 available
character locations will appear.
o
Turn the VFO knob to step through the available characters (A-Z, 0-9 and various
symbols) to choose the first character.
o
Hold S T O R E to store the label.
knob to select the desired memory location.
8
Sending DTMF Tones
The KX3 can generate the Dual-Tone Multi-Frequency (DTMF) tones required to activate special services
available through many repeaters.

Press and hold the PTT to transmit.

Tap F R E Q E N T . DTMF ON will appear in the VFO B area of the LCD.

Press the following keys to enter the needed characters. The tone will continue as long as each key
is pressed. To disable the DTMF keys, release the PTT or tap F R E Q E N T .
Character Press
0 – 9 Numbered keys
*
AT U T U N E
#
MSG
A
MODE
B
A/ B
C
D AT A
D
A> B
Channel Hopping (Scanning)
Scanning or manually tuning across a group of frequencies stored in memory is referred to as channel
hopping. This is especially useful to monitor repeaters and specific simplex frequencies. Set up the KX3 for
channel hopping as follows:

Store all of the frequencies you want to monitor in successive memory locations anywhere between
0 and 99 with an asterisk (*) as the first character of each label. Note that these memory locations
must be successively numbered locations with no gaps and all of the frequencies must be within the
same band. You can include frequencies within the band that use different modes such as SSB, AM
or CW.

Tune to any one of the memorized locations by holding R C L (recall) and turning the VFO knob
to select one of the memory locations or by clicking on the QSY radio button in the Frequency
Editor while it is connected to the KX3.

Turn the VFO knob to step the KX3 through the frequencies in the memory locations or press
to initiate a live scan across those frequencies. Tap any switch to stop the live scan.
S C AN

Tap R AT E or change bands to disable channel hopping.
Monitoring the Repeater Input Frequency
The KX3 allows you to quickly check the repeater input frequency (your transmit frequency) to check for
interference. With the KX3 ready to transmit on a repeater, hold R E V . The VFO A display will switch to
the repeater input frequency and you will hear any audible signals present. Hold R E V again to return to
normal operation.
Be sure you hold R E V a second time to switch back to normal operation before
transmitting.
9
Sleep Mode
Sleep mode allows you to reduce the added current drain of the 2M or 4M module by up to 50% while
monitoring a frequency with the receiver squelched. The 2M or 4M module is switched off and reawakened at intervals to check for any activity on the frequency.

Hold M E N U and then select 2M/4M with the VFO
always on).

Use the VFO knob to select the desired time in seconds between checks for a signal: SLEEP .25,
.50, .75 or 1.0. For example, SLEEP .50 means the KX3 will wake up and check the frequency for
knob. The default setting is nor (receiver
a signal every half (0.5) second.
Troubleshooting
General KX3 troubleshooting suggestions are included in the KX3 Owner’s manual. The most common
symptoms and their causes relating to the KX3-2M or KX3-4M modules are listed below. If the problem
persists, contact Elecraft Customer Support (page 30) or post a question on the Elecraft e-mail reflector.
Be sure you completed all of the settings under Configuring the KX3 for the KX32M or KX3-4M Module on page 3.

No FM output: Verify that FM Mode enabled in menu: Hold M E N U , turn the VFO
knob to On.
MODE and turn the VFO

RF Output Decreases After Short Transmission or Poor Receive Sensitivity: Ensure the screw
securing the 2M or 4M module to the KX3 end plate is in place and snug (see Figure 22 on page
28). You will need to open the KX3 as if you were changing batteries to see the screw. This screw
is essential to avoid overheating the power output transistor in the 2M or 4M module. You can
monitor the temperature change while transmitting. Tap D I S P L AY and turn the VFO knob to
display PA.2 in the VFO B area of the LCD. The temperature is shown in Celsius.

VFO Tuning Noise Heard in Speaker or Phones: Hold M E N U , turn the VFO knob to VFO NR
(VFO Noise Reduction) and turn the VFO knob to On. Optionally, in the menu set RX SHFT to
8.0. Even with these settings, there may be very weak noise heard. If your KX3 is equipped with
the KXFL3 roofing filer and was purchased prior to January 2014, check to be sure the KXFL3
board was modified as described in the Elecraft KX3 VFO Tuning Noise Suppression Modification
document available on the Elecraft web site.

Weak or Distorted Audio in FM Mode: Check for proper microphone gain level. Press the
microphone PTT switch and, while speaking normally into the microphone, adjust the
KEYER/MIC control for 5 or 6 bars indicated on the LCD ALC display as shown in Figure 1. Check
that your deviation matches the receiving station (or repeater). For optimum results the deviation
used at the transmitting station must match the deviation expected by the receiving station. If the
deviation is too low the audio may sound weak. If the deviation is too high, the audio may be
broken up and distorted. See Frequency Deviation on page 6 if you need to adjust the deviation.

Unable to Access Repeaters: If you are sure you are in a location where your signal should bring
up the repeater, check to ensure you are using the correct PL tone, that the PL tone is enabled for
transmit and that the offset and offset sign are correct (see Repeater Operation starting on page 6).
Be sure the Offset shown on the display (see Figure 1on page 5) is correct for the repeater.
10
knob to FM

Unable to Hold Repeater While Transmitting: The most common cause is a weak signal. But if
you are sure you are in an area where your signal should be strong at the repeater, over deviation
may cause the repeater to shut off. Check with the repeater operator to determine the proper
deviation for your voice and for the PL tone or tone burst (if used). If needed adjust the KX3
deviation as described under Frequency Deviation on page 6. Note that there are separate
adjustments for voice and PL or tone burst deviation.

Wattmeter: The wattmeter is calibrated at the factory. If you feel you have a more accurate lowpower VHF wattmeter or spectrum analyzer and an accurate VHF 50-ohm dummy load, you can
adjust the wattmeter calibration. To adjust the wattmeter, hold M E N U and then turn the VFO
knob to WMTR XV (transverter wattmeter). Note the default value in case you decide to return to it.
Hold KHZ until UNLOCK appears briefly in the VFO B display area and turn the VFO knob to
change the wattmeter reading. Turn the knob counter-clockwise to increase the power output or
clockwise to decrease the power output. Transmit to see the change and repeat as needed.
Circuit Description
The KX3-2M transverter operates at an I.F. frequency in the 48 MHz range while the KX3-4M transverter
operates at an I.F. frequency in the 23 MHz range.
J1 connects the I.F. signals to the KX3. The IF signal passes through a low-pass filter to a CMOS SPDT
switch.
When transmitting, the CMOS switch passes the I.F. signal through an attenuator (approximately 25 dB).
The attenuator allows the KX3 to operate at drive levels high enough to provide accurate power metering.
The CMOS switch bypasses the attenuator when receiving.
A high-performance double-balanced mixer converts the I.F. to the 2M or 4M band using a local oscillator
signal supplied by the KX3 via J4. High-side injection is used on 2 meters, so when the KX3 VFO is set to
144 MHz indicated on the display, the local oscillator frequency is 192 MHz to produce an I.F. frequency
in the 48 MHz range. Similarly, high-side injection is used on 4 meters (70 MHz) to produce an I.F.
frequency in the 23 MHz range.
Another single-pole double-throw CMOS switch connects the mixer to the transmit or receive signal path.
In transmit mode, the signal passes through three stages of amplification and then on to the antenna
connector J3 through a diode antenna switch and a low-pass filter.
The diode antenna switch uses two diodes connected so that when one is forward biased to pass the signal,
the other is reverse biased to block the signal. Switching the bias connects the antenna to either the transmit
or receive signal path.
In receive mode, the signal from the antenna connector is routed through the antenna switch to a low-noise
amplifier and then through the single-pole, double throw CMOS switch to the mixer.
The mixer converts the incoming signal to the I.F. and passes it directly to the next CMOS switch,
bypassing the transmit signal attenuator, and then on to I.F. connector J1.
11
Installing the KX3-2M or 4M Module
Preparing for Installation
Preventing Electrostatic Discharge Damage
ESD damage may occur with static discharges far too little for you to notice. A damaged component may
not fail completely at first. Instead, the damage may result in below-normal performance for an extended
period of time before you experience a total failure.
We strongly recommend you take the following anti-static precautions (listed in order of importance) to
ensure there is no voltage difference between the components and any object that touches them:

Leave the KX3-2M or 4M PC board in its anti-static packaging until you install it.

Wear a conductive wrist strap with a series 1-megohm resistor that will constantly drain off any
static charge that accumulates on your body. If you do not have a wrist strap, touch a ground
briefly before touching any sensitive parts to discharge your body. Do this frequently while you
are working. You can collect a destructive static charge on your body just sitting at the work
bench.
WARNING
DO NOT attach a ground directly to yourself without a current-limiting resistor as this
poses a serious shock hazard. A wrist strap must include a 1-megohm resistor to limit the
current flow. If you choose to touch an unpainted, metal ground to discharge yourself, do it
only when you are not touching live circuits with any part of your body.

Use a grounded anti-static mat on your work bench (see below).

If you pick up a PC board that was not placed on an anti-static mat or in an anti-static package,
touch first a ground plane connection on the board such as a connector shell or mounting point.

If you use a soldering iron to work on a circuit board, be sure your iron has an ESD-safe grounded
tip tied to the same common ground used by your mat and wrist strap.
Choosing an Anti-Static Mat
An anti-static mat must bleed off any charge that comes in contact with it at a rate slow enough to avoid a
shock or short circuit hazard but fast enough to ensure dangerous charges cannot accumulate. Typically, a
mat will have a resistance of up to 1 Gigaohm (109 ohms). Testing a mat requires specialized equipment, so
we recommend that you choose an anti-static mat that comes with published resistance specifications and
clean it as recommended by the manufacturer. Testing has shown that many inexpensive mats that do not
specify their resistance have resistance values much too high to provide adequate protection, even after
they were cleaned and treated with special anti-static mat solutions.
Suitable anti-static table mats are available from many sources including:

U-line (Model 12743 specified at 107 ohms)

Desco (Model 66164, specified at 106 to 108 ohms)

3MTM Portable Service Kit (Model 8505 or 8507, specified at 106 to 109 ohms)
12
Tools Required
1. ESD Protection (see Preventing Electrostatic Discharge Damage, page 12).
2. #1 size Phillips screwdrivers. To avoid damaging screws and nuts, a power screwdriver is not
recommended.
3. Long Nose Pliers.
4. Soft cloth or clean, soft static dissipating pad to avoid scratching the enclosure.
5. Optional: 5/16” wrench for tightening the antenna connector nut (see Figure 11 on page 19).
Parts Supplied
Be sure you have the following components in your kit. If anything is missing, contact Elecraft customer
support (page 18).
KX3-2M or 4M Transverter Assembly Bag (E850580)
ILLUSTRATION
DESCRIPTION
QTY.
Printed Circuit Board
ESD SENSITIVE! Leave it in its
anti-static envelope until it is
installed.
ELECRAFT
PART NO.
KX3-2M
E850580
1
KX3-4M
E850648
Shield
Label will be checked to indicate
whether the module is for 2M or 4M.
1
E850636
Adapter Board
The adapter board is required only if your KX3 is not with the KXAT3 Antenna Tuner option.
ILLUSTRATION
DESCRIPTION
KX3-2M or 4M Adapter Board
13
QTY.
ELECRAFT
PART NO.
1
E850633
Hardware Bag, KX3-2M or 4M (E850635)
QTY.
ELECRAFT
PART NO.
Lock Washer, #4
4
E700004
Spacer, M-F
2
E700304
Screw, Pan Head, Stainless Steel,
4-40, 5/32” (4.0 mm)
2
E700302
Screw, Flat Head
1
E700253
Coaxial Cable, Local Oscillator
1
E980255
1
E850634
ILLUSTRATION
DESCRIPTION
KX2-M Antenna Cable Assembly
The connector on your cable may look
different from that shown.
14
Installation Procedure
The KX3-2M or 4M module mounts over the exposed area of the RF board in the bottom cover next to the
battery holders. It mounts above the KXAT3 Antenna Tuner. An adapter board is included in the kit for
those KX3s that do not have the optional Antenna Tuner.
Figure 3. KX3-2M or 4M Module Installed in the KX3.
Separate the Case Halves
Disconnect all cables attached to the KX3 and remove the KXPD3 paddles if installed.
Open the KX3 just as you would to install or remove batteries (see Internal Batteries in your
Owner’s Manual for details about how to do this).
Remove the internal batteries (if present).
We recommend removing the batteries whenever you work inside of your
KX3 to avoid damage that may be caused by an accidental short circuit.
15
Separate the two halves of the KX3 case by unplugging the battery cable and unplugging the flex cable
at the end next to the battery holders as shown in Figure 4. Gently lift up on each end of the flex cable
connector and rock it side to side to unplug it. When free, set the front panel assembly aside.
Figure 4. Disconnecting the Flex and Battery Cables.
Install the Internal Coaxial Cables
Two miniature coaxial cables are used to carry RF signals. One cable carries a local oscillator signal from
the KX3 main RF board to the KX3-2M or 4M module. The second cable carries RF signals between the
KX3-2M or 4M module and an SMA antenna connector mounted on the end panel of the KX3 near the
BNC antenna connector. The coaxial cables are equipped with female Ultra Miniature Coaxial (UMC)
connectors that snap onto male UMC connectors on the KX3 RF board and the KX3-2M or 4M module
(see Figure 5).
Figure 5. Miniature Coaxial Connectors.
16
Installing the Antenna Coaxial Cable
Remove the KXAT3 Antenna Tuner board as follows. If your KX3 is not equipped with the KXAT3, skip
the following steps and go directly to installing the antenna cable on page 18.
On the KXAT3 module, unplug the connector for the cable leading to the BNC connector as shown in
Figure 6. You can use long-nose pliers to grip the connector as shown in Figure 7.
If using the pliers, take care not to damage the pc board or components.
Remove the two screws and lock washers shown in Figure 6.
Lift the KXAT3 board out, unplugging it from the two connectors shown in Figure 6. Set the KXAT3
board aside in an ESD-safe place.
Figure 6. Removing the KXAT3 ATU.
17
Figure 7. Using Long-Nose Pliers to Grip the H.F. Antenna Wire.
Install the antenna coaxial cable and SMA connector as follows:
Remove the plastic plug from the hole in the end of the KX3 enclosure near the BNC connector. This
is most easily done with your long-nose pliers.
Figure 8. Removing the Hole Plug.
Check the inside surface of the KX3 end panel. The surface should be clean metal free of paint or
masking tape as shown in Figure 8. This is important to provide a good ground for the antenna connector
and good contact for the KX3-2M or 4M module power transistor heat sink.
In the unlikely event you need to clean the metal surface, hold the KX3 with the end
downward so any debris from the cleaning will not fall on to the PC board.
Check the inside surface of the hole from which you removed the plug (Figure 8). The inside edge
must be free of paint or tape; otherwise the antenna connector will not fit. If needed scrape the surface
clean, taking care not to scratch the outside surface of the end panel or allow debris to fall inside the KX3
18
Locate the miniature coaxial cable with the SMA connector at one end. If the connector has a nut and
lock washer on it (see Figure 9), remove only the nut, sliding it down and off the end of the coax. If your
connector does not have the nut and lock washer on it, locate them in the hardware bag and slide the lock
washer onto the connector.
If the nut turns stiffly due to the solder at the end of the threaded section, thread it
on and off again several times so it turns very smoothly. That will make the installation
of the connector easier in the following the steps.
Figure 9. Preparing the SMA Connector for Installation.
One side of the SMA connector is flat. When you install it in the next step, align the
flat side of the connector with the flat side of the D-shaped hole in the end panel.
Thread the coaxial cable through the hole in the end panel that was occupied by the plug you removed.
Before fitting the connector through hole in the end panel, slide one lock washer and the nut over the coax
until they rest in the gap at the end of the PC board as shown in Figure 10 and then start the nut onto the
SMA connector threads as you slide it through the hole. Be sure the connector does not touch L43 or L40
on the KX3 RF board. If needed, move the inductors slightly to provide clearance as shown in Figure 11.
There is a solder-filled via on the RF board directly under the connector. That via is a ground connection
between the top and bottom of the RF board so it doesn’t matter if it touches the SMA connector.
Figure 10. Installing the SMA Antenna Connector.
19
Figure 11. Positioning L40 or L43 to Provide Clearance.
Installing the Local Oscillator Coaxial Cable
If your KX3 is equipped with the optional KXFL3 Filter option, remove the KXFL3 board as shown
in Figure 12. Set it aside in an ESD-safe place.
CAUTION
Do not press on the large rectangular gray capacitors. Doing so may detune the filter
and require that you re-align it as described in the KXFL3 manual when it is
reinstalled.
Figure 12. Removing the KXFL3 Filter option board.
20
Install the local oscillator cable as follows:
If you have difficulty with the following steps to mate the ultra miniature
coax connectors, a short video is available on the Elecraft web site at:
http://www.elecraft.com/KX3/kx3.htm. Scroll down to UMCC Connector
Montage near the bottom of the web page.
Locate the coaxial cable with a miniature connector on each end. Plug one end of the cable into J4 on
the KX3 RF board as follows:

Shape the end of the cable as shown in Figure 13 to it can be easily placed directly onto J4.

Carefully align the cable over the connector and press down on the connector. It will require
significant force to mate the connectors, especially when they are new. Press on the connector
directly over J4 using a plastic tool such as a pen (see Figure 14) .Take care to press directly on the
back of the connector above J4. You will hear and feel a distinct “snap” when they are mated and,
of course, the connector will resist being pulled off of J4.
Figure 13. Mating the Ultra Miniature Coaxial Connector at J4.
Turn the coaxial connector as shown in Figure 14 so the metal part cannot touch C180 on the printed
circuit board. If the connector is properly mated you can rotate it without the connector disconnecting.
Route the coaxial cable toward the end of the KX3 that has the antenna connector as shown.
21
Figure 14. Orienting the Cable at J4..
If you removed the KXFL3 filter board (see Figure 12 on page 20), replace it now. Replace the
retaining screw and ensure it passes into the hole in the KXFL3 board.
22
Prepare the KX3 for the KX3-2M or 4M Module
The KX3-2M or 4M PC board mounts on top of the KXAT3 Antenna Tuner board. If you do not have the
KXAT3 option installed, your kit will include an adapter board to install in place of the KXAT3.
If you do not have the KXAT3 Antenna Tuner installed, disconnect the HF antenna cable from the
main RF board as shown in Figure 15.
Figure 15. Disconnecting the Antenna Cable from the Main RF Board.
Route the antenna coax cable across the RF board, between the toroidal inductors and alongside the
standoff exactly as shown in Figure 16.
Figure 16. Routing the Antenna Coax.
23
Replace the KXAT3 board as shown in Figure 17 or, if your KX3 is not equipped with the KXAT3
Antenna Tuner option, install the adapter board furnished in its place. Do not disturb the location of the
antenna coax you just positioned.

There are two multi-pin connectors on the KXAT3 or on the adapter board. Be sure they are
properly mated with the corresponding connector(s) on the RF board below as shown in the figure.

Reconnect the HF antenna cable. The two pins are tied together electrically so the connector may
be inserted with the pins oriented either way.

Secure the KXAT3 or adapter board using the two M-F standoffs and lock-washers. Place the lock
washers under the standoffs as shown in Figure 18.
CAUTION
Tighten the M-F standoffs only enough to compress the lock washers. The standoffs
are aluminum and you can easily twist the threaded shaft off of the rest of the
standoff.
Figure 17. Replacing the KXAT3 ATU.
Figure 18. KXAT3 or Adapter Mounting Hardware.
24
Installing the KX3-2M or 4M Board
Since attaching the coaxial connectors takes significant force, be careful not to damage the KX3-2M or 4M
board or any of the components on it when attaching the cables to it. The connectors for the antenna and
local oscillator coaxial cables are on the side of the board that faces downward toward the KX3 RF board
when it is installed, so the coaxial cables must be attached first. The locations of the coaxial connectors on
the KX3-2M or 4M board are shown in Figure 19. Note that the KX3-2M or 4M board has no components
directly behind the coaxial connectors. That allows you to place a solid object behind the PC board to
support it while pressing the coaxial cable connectors in place as described below.
CAUTION
Do not try to attach the coaxial cables without supporting the board to avoid stressing
the board or the components. The connectors will require as much force as you used
on the L.O. connector earlier. Failure to provide good support may destroy the KX32M or 4M board.
Figure 19. KX3-2M or 4M Board Coaxial Connector Locations.
25
Attach the coaxial cables to the KX3-2M or 4M board as follows:
Connect the local oscillator coaxial cable to the L.O. connector (J4) on the KX3-2M or 4M board
using a solid object to support the board from behind while you press the connector in place with a tool
such as a plastic pen just as you did before at L.O connector J4. Figure 20 shows a common pencil used to
support the board but any solid support that rests directly against the printed circuit board and not the
components on the board is suitable.
Figure 20. Attaching the Local Oscillator Cable to the KX3-2M or 4M Board.
26
Connect the antenna coax to the ANT connector (J3) on the KX3-2M or 4M board as shown in
Figure 21.
Figure 21. Attaching the Antenna Coax to the KX3-2M or 4M Board.
Install the KX3-2M or 4M board in the KX3 as follows:
Mount the KX3-2M or 4M board on the KXAT3 Antenna Tuner board or, if no antenna tuner, the
adapter board you installed earlier:

Orient the board as shown in Figure 22.

There are two multi-pin connectors that mate with connectors on the KXAT3 (or adapter) board.
Be sure all the pins engage.

Secure the KX3-2M or 4M board with three screws as shown in Figure 22. Use the stainless steel
5/16” (7.9 mm) pan head screws provided, not the black 3/16” (4.8 mm) pan head screws that were
originally used to hold the KXAT3 board.
CAUTION
Be certain you install the black flat head screw that threads into the transistor heat
sink. Failure to install this screw will cause the KX3-2M or 4M to shut down after a
very short period of operation due to excessive heating of the final transistor.
Tuck the local oscillator coax into the space between the heat sink and the battery holders..
27
Figure 22. Mounting the KX3-2M or 4M Board in the KX3
If you have the KXAT3 installed, route the antenna coax to the KX3-2M or 4M board around the end
as shown in Figure 23. Be sure the coaxial cable does not pass over either of the nearby toroidal
inductors.
Figure 23. Routing the Antenna Coax Between the KXAT3 Inductors
Locate the notch on one side of the shield (see Figure 24). The notch is required to clear solder pads
on the KX3-2M or 4M board.
28
Figure 24. Shield Notch Location.
Place the shield over the metal frame on the KX3-2M or 4M board oriented as shown in Figure 25,
and press it down so the small bumps on the frame are in the holes along all four sides of the shield. The
bumps latch the shield in place.
Do not operate your KX3-2M or 4M with the shield removed. It is required to
provide essential isolation between circuits.
Figure 25. Installing the Shield.
Reassemble the KX3 enclosure (see Figure 4)
 Reconnect the ribbon cable.
 Reconnect the battery cable.
 Replace the batteries (if used).
 Close the case.
That completes the installation of your KX3-2M or 4M module.
29
Customer Service and Support
Technical Assistance
You can send e-mail to k3support@elecraft.com and we will respond quickly – typically the same day
Monday through Friday. If you need replacement parts, send an e-mail to parts@elecraft.com. Telephone
assistance is available from 9 A.M. to 5 P.M. Pacific time (weekdays only) at 831-763-4211. Please use email rather than calling when possible since this gives us a written record of the details of your problem and
allows us to handle a larger number of requests each day.
Repair / Alignment Service
If necessary, you may return your Elecraft product to us for repair or alignment. (Note: We offer unlimited
email and phone support, so please try that route first as we can usually help you find the problem quickly.)
IMPORTANT: You must contact Elecraft before mailing your product to obtain authorization for the
return, what address to ship it to and current information on repair fees and turnaround times. (Frequently
we can determine the cause of your problem and save you the trouble of shipping it back to us.) Our repair
location is different from our factory location in Aptos. We will give you the address to ship your kit to at
the time of repair authorization. Packages shipped to Aptos without authorization will incur an additional
shipping charge for reshipment from Aptos to our repair depot.
Elecraft 1-Year Limited Warranty
This warranty is effective as of the date of first consumer purchase (or if shipped from the factory, the date the
product is shipped to the customer). It covers both our kits and fully assembled products. For kits, before
requesting warranty service, you should fully complete the assembly, carefully following all instructions in the
manual.
Who is covered: This warranty covers the original owner of the Elecraft product as disclosed to Elecraft at the
time of order. Elecraft products transferred by the purchaser to a third party, either by sale, gift, or other method,
who is not disclosed to Elecraft at the time of original order, are not covered by this warranty. If the Elecraft
product is being bought indirectly for a third party, the third party’s name and address must be provided at time
of order to ensure warranty coverage.
What is covered: During the first year after date of purchase, Elecraft will replace defective or missing parts
free of charge (post-paid). We will also correct any malfunction to kits or assembled units caused by defective
parts and materials. Purchaser pays inbound shipping to us for warranty repair; we pay shipping to return the
repaired equipment to you by UPS ground service or equivalent to the continental USA and Canada. For Alaska,
Hawaii, and other destinations outside the U.S. and Canada, actual return shipping cost is paid by the owner.
What is not covered: This warranty does not cover correction of kit assembly errors. It also does not cover
misalignment; repair of damage caused by misuse, negligence, battery leakage or corrosion, or builder
modifications; or any performance malfunctions involving non-Elecraft accessory equipment. The use of acidcore solder, water-soluble flux solder, or any corrosive or conductive flux or solvent will void this warranty in
its entirety. Also not covered is reimbursement for loss of use, inconvenience, customer assembly or alignment
time, or cost of unauthorized service.
Limitation of incidental or consequential damages: This warranty does not extend to non-Elecraft equipment
or components used in conjunction with our products. Any such repair or replacement is the responsibility of the
customer. Elecraft will not be liable for any special, indirect, incidental or consequential damages, including but
not limited to any loss of business or profits.
30