KT-100 OPERATIONS MANUAL MANUAL REV B
LDG KT-100 100-Watt
Automatic Tuner for
Kenwood Transceivers
LDG Electronics
1445 Parran Road
St. Leonard MD 20685-2903 USA
Phone: 410-586-2177
Fax: 410-586-8475
ldg@ldgelectronics.com
www.ldgelectronics.com
PAGE 1
Table Of Contents
Introduction 2
Jumpstart, or “Real hams don’t read manuals!” 2
Specifications 2
An Important Word About Power Levels 2
Important Safety Warning 2
Getting to know your KT-100 2
Front Panel 2
Rear Panel 2
Installation 2
Operation 2
Basic Tuning Operation 2
Operation From the Kenwood Transceiver Front Panel 2
Typical Location of AT Tuning Button on Kenwood Transceivers 2
Operation From the KT-100 Front Panel 2
Tuning on the 6 Meter Band 2
Status Indicators 2
Configuration Options 2
Operating Hints 2
Transceiver Tuner Status Indication 2
Transceiver Tuner “Time-Out” Beep 2
TS-50 Hints 2
TS-2000 Hints 2
TS-480 HX Hints 2
TS-480 SAT Hints 2
TS-450 / TS-690 Hints 2
TS-570 Hints 2
TS-850 Hints 2
TS-870 Hints 2
Application Information 2
Mobile Operation 2
MARS/CAP Coverage 2
Theory of Operation 2
Some basic ideas about impedance 2
Transmitters, transmission lines, antennas, and impedance 2
The LDG KT-100 2
A Word About Tuning Etiquette 2
Care and Maintenance 2
Technical Support 2
Two-Year Transferrable Warranty 2
Out Of Warranty Service 2
Returning Your Product For Service 2
Product Feedback 2
PAGE 2
INTRODUCTION
LDG pioneered the automatic, wide-range switched-L tuner in 1995. From its laboratories in St.
Leonard, Maryland, LDG continues to define the state of the art in this field with innovative
automatic tuners and related products for every amateur need.
Congratulations on selecting the KT-100 100-watt automatic tuner for Kenwood transceivers.
The KT-100 provides semi-automatic antenna tuning across the entire HF spectrum plus 6 meters,
at power levels up to 125 watts. It will tune dipoles, verticals, Yagis, or virtually any coax-fed
antenna. It will match an amazing range of antennas and impedances, far greater than some other
tuners you may have considered, including the built-in tuners on many Kenwood radios.
The KT-100 is similar to previous LDG tuners, but is specially engineered to integrate with your
Kenwood HF radio. The KT-100 connects to the Kenwood AT-300 tuner port on the back of the
radio. Not only is the KT-100 controlled by the radio, it also is powered by the radio, so there is no
additional power cable required to use the KT-100!
JUMPSTART, OR “REAL HAMS DON’T READ MANUALS!”
Ok, but at least read this one section before operating the KT-100:
1. Turn off power to your Kenwood radio.
2. Connect the antenna jack (Antenna “1” on TS-480) on your transceiver to the “TX” jack on the
KT-100, using the supplied 50 ohm coax cable jumper.
3. Connect a 50 ohm coax antenna feedline to the “ANT” jack on the KT-100.
4. Connect the 6-pin end of the supplied radio interface cable to the Antenna Tuner port on the
back of your Kenwood radio.
5. Connect the 7-pin mini-DIN plug end of the supplied radio interface cable to the “Radio” jack
on the back of the KT-100
6. Turn on power to your transceiver and select the desired operating frequency and mode.
7. Push and hold the AT or TUNE button on the front of your transceiver for one second
1
. The
transceiver automatically switches to CW mode, and keys up with a minimal amount of power,
and the KT-100 begins a tuning cycle. At the end of the tuning cycle, the original mode and
power level is restored.
8. Wait for the tuning cycle to end; you’re now ready to operate!
1
Note: Tuning on the 6 meter band requires a different procedure; see section xxxx
PAGE 3
SPECIFICATIONS
0.1 to 125 watt power range (SSB and CW), 100W on 6M.
•
Latching relays for ultra low power operation.
•
2000 memories for instantaneous band changing.
•
Controlled from Kenwood Tuner button on radio. Powered from Kenwood radio.
•
Works with any Kenwood radio that is AT-300 compatible.
•
Partial radio list: TS-50, TS-480
•
Tuning time: 0.1 to 6 seconds full tune, 0.1 seconds memory tune.
•
1.8 to 54.0 MHz coverage. Built-in frequency sensor.
•
Tunes 4 to 800 ohm loads (16 to 150 on 6M), 16 to 3200 ohms with optional 4:1 Balun.
•
For Dipoles, Verticals, Vees, Beams or any Coax Fed Antenna.
•
Optional external Balun allows tuning of random length, long wire or ladder line fed antennas.
•
2
, TS-570, TS-690, TS-850, TS-870, TS-2000.
Includes Kenwood interface cable and coax jumper. Ready to use right out of the box.
•
Dimensions: 6.5L” x 6.5W” x 1.5H”.
•
Weight: 2 pounds
•
AN IMPORTANT WORD ABOUT POWER LEVELS
The KT-100 is rated at 125 watts maximum power input at most. Many ham transmitters and
transceivers, and virtually all amplifiers, output well over 125 watts. Power levels that significantly
exceed specifications will definitely damage or destroy your KT-100. If your tuner fails during
overload, it could also damage your transmitter or transceiver. Be sure to observe the specified
power limitations.
IMPORTANT SAFETY WARNING
Never install antennas or transmission lines over or near power lines. You can be seriously
injured or killed if any part of the antenna, support or transmission line touches a power
line. Always follow this antenna safety rule: the distance to the nearest power line should
be at least twice the length of the longest antenna, transmission line or support dimension.
2
Note: When using the KT-100 with TS-480 HX (200 watt radio), the TS-480HX will only transmit 100 watts. The TS-480HX is
programmed by Kenwood to limit the power to 100 watts when an external tuner is detected. LDG recommends the AT-200 Pro for use with
the TS-480HX, so that the full 200 watts may be realized.
PAGE 4
GETTING TO KNOW YOUR KT-100
Your KT-100 is a quality, precision instrument that will give you many years of outstanding
service; take a few minutes to get to know it.
The KT-100 can be used with any Kenwood transceiver that supports the AT-300 tuner
interface. Tuning is performed when the AT or TUNE button is pushed on the front of the
Kenwood radio and held for one second. The tuner can be placed in bypass mode by pressing the
AT or TUNE button momentarily.
Front Panel
On the front panel there is one pushbutton and two LED indicator lights.
Tune: Initiates either a memory tune or a full tune, and also toggles the tuner between
•
“a
ctive” and “bypass” modes.
LED: Lights steady green at the end of a tuning cycle to indicate a good match has been
SWR
•
found.
match is not found.
Tuning LED: L
•
ights during tuning operation, will also blink error codes if a good tuning
PAGE 5
Rear Panel
The rear panel of the KT-100 features four connectors.
ANT connector: Connect the 50-ohm coax antenna feedline to this standard SO-239
•
connector.
GND connector (wing nut): Connect to antenna system ground.
•
TX connector: Connect the 50-ohm coax jumper cable from this standard SO-239 connector
•
to the ANT jack on the back of the transceiver.
Radio connector: This 7-pin mini-DIN connector connects to the supplied radio interface
•
cable, which connects to the AT-300 tuner port on the transceiver.
PAGE 6
INSTALLATION
The KT-100 tuner is designed for indoor operation only; it is not water resistant. If you use it
outdoors (Field Day, for example), you must protect it from the rain. The KT-100 is designed for
use with coax-fed antennas. If use with longwires or ladder-line-fed antennas is desired, an external
balun is required. The LDG RBA-4:1 or RBA-1:1 is ideal, depending on the antenna and
transmission line used.
Always turn your radio off before plugging or unplugging anything. The radio may be damaged
if cables are connected or disconnected while the power is on.
Connect the HF antenna jack on the transceiver to the TX jack on the back of the KT-100,
using the supplied coax jumper cable, or a similar 50 ohm coax cable rated 125 watts or greater. On
the TS-480 and TS-2000 radios, the KT-100 must be connected to the ANT 1 jack of the
transceiver. The TS-480 and TS-2000 will not initiate an external tuning cycle if ANT 2 is selected.
The internal tuner will be used, instead, on those models equipped with an internal tuner, such as
the TS-480SAT and TS-2000. On models without an internal tuner, pressing AT while ANT 2 is
selected will have no effect.
Connect the supplied radio interface cable to the mini-DIN 7-pin jack on the rear of the KT-
100, marked “Radio”. Connect the other end of this cable to the six-pin AT-300 interface port on
the rear of the transceiver. That connector looks like this:
Grounding the KT-100 tuner will enhance its performance and safety. LDG recommends that
you connect your tuner to a suitable ground; a common ground rod connected to buried radials is
PAGE 7
preferred, but a single ground rod, a cold water pipe, or the screw that holds the cover on an AC
outlet can provide a serviceable ground. LDG strongly recommends the use of a properly installed,
high quality lightning arrestor on all antenna cables.
OPERATION
Basic Tuning Operation
The KT-100 is operated either from the AT / TUNE button on the Kenwood transceiver, or
from the front panel TUNE button on the KT-100 itself. Two types of tuning cycles are available; a
memory tuning cycle and a full tuning cycle.
The memory tuning cycle attempts to tune quickly based on having previously tuned on the
present frequency selection. If the tuner previously was successful in tuning on the currently selected
frequency, the settings for that match will be loaded into the tuner relays, and checked to see that an
acceptable SWR match is found.
A full tuning cycle “starts from scratch” and begins a fixed tuning sequence where the KT-100
rapidly tries varying combinations of inductance and capacitance values, and then zeroes-in on the
best match possible. When the tuning cycle is complete, if an acceptable match was found, the
inductance and capacitance settings are saved in a memory associated with the selected frequency, so
that they may be recalled quickly in the future via a memory tuning cycle.
In this manner, the KT-100 “learns”; the longer you use it, the more closely it adapts itself to the
bands and frequencies you use. Most users will probably use memory tuning most of the time; it
takes advantage of any saved tuning settings, but automatically defaults to a full tuning cycle if no
stored data is available.
In both cases, at the end of the tuning cycle, the carrier is held for 1.5 seconds after tuning is
complete, so that the final SWR may be read on the transceiver’s internal SWR meter or another
inline SWR meter, and the front panel LEDs will indicate the status of the tuning cycle.
Operation From the Kenwood Transceiver Front Panel
To initiate a tuning sequence from the Kenwood transceiver, press and hold the AT button for
one second. The radio will switch to CW mode, reduce power, and begin to transmit a carrier. The
KT-100 will begin a memory tuning sequence as described above. If an acceptable SWR match is
found in the memory tuning cycle, the tuning cycle ends. Otherwise, the KT-100 automatically
begins a full tuning cycle in an attempt to find a good match. If the full tuning cycle is then
successful, the match is stored in a memory associated with the selected frequency.
When the tuning cycle is complete, an indicator on the display of the transceiver will show that
the tuner is active. This indicator varies by model; consult the transceiver owner’s manual for details
on operation with an external automatic tuner.
To bypass the tuner via the Kenwood transceiver front panel, press the AT button momentarily.
The red LED on the KT-100 will blink once to indicate it is in bypass mode. The tuning indicator
on the front panel of the transceiver will also extinguish.
NOTE: On some models of Kenwood transceiver, an error beep may occur near the end of the
tuning cycle, indicating the tuning cycle is taking a little longer than expected. This is normal and is
no cause for alarm. The KT-100 matches a much broader range of antennas than Kenwood’s own
tuners, and so may take a little longer to find a match.
PAGE 8
PAGE 9
Typical Location of AT Tuning Button on Kenwood Transceivers
Typically, the tuning button on the transceiver front panel is labelled “AT” or “TUNE”. The
following pictures show the location of this button on two popular Kenwood transceivers.
TS-480 “AT” Button location
TS-2000 “AT” Button location
PAGE 10
Operation From the KT-100 Front Panel
Normally, the KT-100 is best operated from the transceiver front panel AT button, but there are
certain circumstances in which operating from the KT-100 front panel gives more control. There are
three operations which can be carried out by use of the front panel button on the KT-100: Toggle
bypass mode, start a memory tune, or force a full tune:
Toggle Bypass Mode: To toggle between bypassed and active mode, press the front panel
•
Tune button on the KT-100 momentarily. The Tuning LED will flash once to indicate that the
tuner is in bypass mode. Press the front panel Tune button momentarily again to recall the
previous tuner settings. The Tuning LED will flash three times to indicate that the tuner is no
longer bypassed. This function may be useful if you wish to compare antenna performance with
and without the benefit of the tuner’s matching network.
PAGE 11
Initiate a Memory Tune Cycle: To initiate a memory tuning cycle using the front panel of
•
the KT-100, you must first change the radio’s mode to one of the continuous carrier modes, such
as AM, CW, or FM. Next, reduce output power to below 100 watts. Press and hold the Tuning
button on the front of the KT-100 until the Tuning LED lights up. Release the button and key
the transmitter. A memory tuning cycle will begin. When tuning is complete, you may return to the
operating mode and power level previously set.
PAGE 12
Force a Full Tune Cycle: Sometimes, if you are transmitting on a previously tuned
•
frequency, but something has slightly changed in your antenna system (maybe the antenna was reoriented, for example), performing a memory recall tune will find a stored match that is
acceptable, but is not as optimal as could be. In this case, forcing a full tune will cause the KT-100
to seek a better match than the match already stored in memory for this frequency.
To force a full tuning cycle, you must first change the radio’s mode to one of the continuous
carrier modes, such as AM, CW, or FM. Next, reduce output power to below 100 watts. Press and
hold the Tune button on the front panel of the KT-100 until the Tuning LED lights up, and
keep holding until the Tuning LED goes out again. Release the Tune button once the Tuning
LED goes out, and then begin transmitting on the radio. A full tuning cycle will begin. When
tuning is complete, you may stop transmitting and return the transceiver to its previous operating
mode and power level.
Tuning on the 6 Meter Band
When Kenwood designed their own external anten
operation, and so most Kenwood transceivers that are co
na tuners, they did not include 6 meter
mpatible with the KT-100 will not allow
the pressing of the AT button to initiate a tuning cycle when operating on 6 meters. When tuning
on the 6 me ns for Operatio n
beginning on page 10. In other words, when tuning on
ter band, follow the instructio n From the Front Panel of the KT-100 as show
6 meters, the KT-100 front panel button
must be used.
PAGE 13
Status Indicators
The SWR LED and Tuning LED are both used to indicate both operating modes, tuning
status, and error codes. The following table lists the LED status codes and their meaning.
LED Indication Meaning
Tuning LED blinks continuously.
Tuning LED on. Tuner is tuning.
Tuning LED goes out, SWR LED comes
on solid.
Tuning LED goes out, SWR LED blinks 5
times.
Tuning LED goes out, no SWR LED.
Tuning LED blinks 4 times. Tuning cycle failed, no RF was detected.
Tuning LED blinks 5 times.
No compatible Kenwood Transceiver is
detected. Check interface cable connections.
Tuner has completed a tuning cycle; a
good SWR match was found.
Tuning cycle is complete, tuning match is
between 1.5:1 and 3.0:1 SWR.
Tuning cycle is complete, tuning match is
between greater than 3.0:1 SWR.
Tuning cycle failed, RF was lost in the
middle of the tune.
Configuration Options
There are no configuration options for the KT-100. It’s truly plug-and-play!
OPERATING HINTS
This section describes a few practical tips on using the KT-100 tuner with Kenwood
transceivers.
Transceiver Tuner Status Indication
The various models of Kenwood transceivers all indicate the status of the external tuner a little
diff
erently. Most will show an graphical or textual icon on the screen to indicate that the tuner is
engaged and has properly tuned. For example, the TS-480 displays a flashing “ R < AT >T ” whi
tuning, and a solid “ R < AT >T ” when tuning is co
bypassed. Other Kenwo
od transceivers behave similarly. Consult your transceiver operating
mplete. This icon disappears when the tuner is
le
manual’s section on use with external tuners for more information.
PAGE 14
Transceiver Tuner “Time-Out” Beep
Certain models of Kenwood transceivers will begin beeping if a tuning cycle takes longer than a
certain amoun
t of time. This is normal with the KT-100, as some tuning cycles may last for several
seconds.
TS-50 Hints
When usin
g the KT-100 with a TS-50 transceiver, the radio will beep out the word “CHECK”
(-.-. .... . -.-. -.-) in Morse Code when the tuner is bypassed. This is normal.
TS-2000 Hints
When using the KT-100 with a TS-2000, be sure to hook the KT-100 to the ANT 1 jack of the
TS-2000. The internal tuner of the TS-2000 will still continue to function when ANT 2 is selected.
TS-480 HX Hints
If using a
TS-480HX with the KT-100, the TS-480HX will limit its transmit power to 100 watts
maximum, on both antenna ports. LDG recommends using the AT-200 Pro instead.
TS-480 SAT Hints
When using the KT-100 with a TS-480SAT, hook the KT-100 to the ANT 1 jack of the TS480SAT. Set menu #27, “EXTERNAL AT OPERATION MODE” to “At1”. You will have to
power off and back on for this setting to take effect.
TS-450 / TS-690 Hints
When using the KT-100 with the TS-450 or TS-690 radios, the radio will need to be configured
to use an external tuner. To do this, hold down the ENT key when turning on the radio, then turn
the M.CH / VFO CH knob to select menu number 01 on the display. Use UP/DOWN to select
“On” on the display. Press the CLR key. This initializes the TS-450/690 to use an external antenna
tuner, and disables the internal tuner. When tuning, be sure the CAR control is not rotated fully
counterclockwise.
TS-570 Hints
When using the KT-100 with the TS-570 radio, be sure to connect the KT-100 to the ANT 1
port on the TS-570.
TS-850 Hints
When using the KT-100 with the TS-850, switch SW 1 on the rear of the transceiver must be set
to EXT. This selects external tuner mode, and disables the internal antenna tuner.
The THRU/AUTO switch must be set to AUTO. Flip the AT TUNE switch to ON to begin
a tuning cycle. Note that the CAR control must not be rotated fully counterclockwise, otherwise the
tuning cycle will not work.
TS-870 Hints
When connecting the KT-100 to a TS-870, the KT-100 must be connected to the ANT 1 jack
on the rear of the TS-870. The ANT 1 jack must also be selected before tuning. Press
THRU/AUTO first, then press AT TUNE to begin a tuning cycle. ON AIR and AT TUNE
LEDs will light during a tuning cycle on the TS-870. If tuning takes more than 20 seconds, either a
triple beep or a Morse code “CHECK” alarm will sound. This is normal operation.
PAGE 15
APPLICATION INFORMATION
Mobile Operation
The KT-100 is perfectly suited to mobile operation. It can be installed under the dashboard
along with the transceiver, or mounted remotely. The only requirement is that the tuner remain dry.
The supplied radio interface cable is 14 inches long. If it is desired that the KT-100 is positioned
farther from the transceiver than this cable length allows, a custom cable will need to be constructed.
This can be accomplished in two ways: Cut the supplied cable and solder a jumper wire between all
the connections, or purchase new
connectors and cable to construct a
custom-length interface cable from
scratch.
The 6-pin AT-300 interface
connector is Kenwood Part Number
E09-0672-08, available from several
Kenwood replacement part dealers. The
7-pin KT-100 interface connector is
Kycon Connector Part Number
KMDAX-7P, available from
http://www.mouser.com/ as Mouser
part number 806-KMDAX-7P.
MARS/CAP Coverage
The KT-100 provides continuous
tuning coverage over its specified range;
not just in the ham bands. This makes it
useful for MARS or CAP operation, or
any other legal HF operation.
THEORY OF OPERATION
Some basic ideas about impedance
The theory underlying antennas and
transmission lines is fairly complex, and
in fact employs a mathematical notation called “complex numbers” that have “real” and “imaginary”
3
parts. It is beyond the scope of this manual to present a tutorial on this subject
, but a little
background will help in understanding what the KT-100 is doing, and how it does it.
In simple DC circuits, the wire resists current flow, converting some of it into heat. The
relationship between voltage, current, and resistance is described by the elegant and well-known
“Ohm’s Law”, named for Georg Simon Ohm of Germany, who first discovered the principle in
1826. In RF circuits, an analogous but more complicated relationship exists.
RF circuits also resist the flow of electricity. However, the presence of capacitive and inductive
elements causes the voltage to lead or lag the current, respectively. In RF circuits, this resistance to
3
For a very complete treatment of this subject, see any edition of the ARRL Handbook for Radio Communications (previously the
Handbook For Radio Amateurs).
PAGE 16
the flow of electricity is called “impedance”, and can include all three elements: resistive, capacitive,
and inductive.
The output circuit of a transmitter consists of inductors and capacitors, usually in a
series/parallel configuration called a “pi network”. The transmission line can be thought of as a long
string of capacitors and inductors in series/parallel, and the antenna is a kind of resonant circuit. At
any given RF frequency, each of these can exhibit resistance, and impedance in the form of
capacitive or inductive “reactance”.
Transmitters, transmission lines, antennas, and impedance
The output circuit of a transmitter, the transmission line, and the antenna, all have a
characteristic impedance. For reasons beyond the scope of this document, the standard impedance is
nominally 50 ohms resistive, with zero capacitive and zero inductive components. When all three
parts of the system have the same impedance, the system is said to be “matched”, and maximum
transfer of power from the transmitter to the antenna occurs. While the transmitter output circuit
and transmission line are of fixed, carefully designed impedance, the antenna presents 50-ohm, nonreactive load only at its natural resonant frequencies. At other frequencies, it will exhibit capacitive
or inductive reactance, causing it to have an impedance other than 50 ohms.
When the impedance of the antenna is different from that of the transmitter and transmission
line, a “mismatch” is said to exist. In this case, some of the RF energy from the transmitter is
reflected from the antenna back down the transmission line and into the transmitter. If this reflected
energy is strong enough, it can damage the transmitter’s output circuits.
The ratio of transmitted to reflected energy is called the “standing wave ratio”, or SWR. An
SWR of 1 (sometimes written 1:1) indicates a perfect match. As more energy is reflected, the SWR
increases to 2, 3, or higher. As a general rule, modern solid state transmitters must operate with an
SWR of 2 or less. Tube exciters are somewhat more tolerant of high SWR. If a 50 ohm antenna is
resonant at the operating frequency, it will show an SWR close to 1. However, this is usually not the
case; operators often need to transmit at frequencies other than resonance, resulting in a reactive
antenna and a higher SWR.
R
SWR =
1+
1−
F
R
F
where F = Forward power (watts), R = Reflected powe
r (watts)
PAGE 17
FWD
P
(watts)
1617.94
6.42
4.44
3.60
3.14 2.83 2.62 2.46
2.33
48
97.99
17.94 10.63 7.87 6.42
5.51
SWR is measured using a device called an “SWR bridge”, inserted in the transmission line
between the transmitter and the antenna.
This circuit measures forward and reflected
power from which SWR may be calculated
(some meters calculate SWR for you). More
advanced units can measure forward and
reflected power simultaneously, and show
these values and SWR at the same time.
An antenna tuner is a device used to
cancel out the effects of antenna reactance.
REV 20 30 40 50 60 70 80 90 100
2 1.92 1.70 1.58 1.50 1.45 1.41 1.38 1.35 1.33
4 2.62 2.15 1.92 1.79 1.70 1.63 1.58 1.53 1.50
6 3.42 2.62 2.26 2.06 1.92 1.83 1.75 1.70 1.65
8 4.44 3.14 2.62 2.33 2.15 2.02 1.92 1.85 1.79
10 5.83 3.73 3.00 2.62 2.38 2.22 2.09 2.00 1.92
12 7.87 4.44 3.42 2.92 2.62 2.41 2.26 2.15 2.06
14 11.24 5.31 3.90 3.25 2.87 2.62 2.44 2.30 2.20
ower
Tuners add capacitance to cancel out
inductive reactance in the antenna, and vice
versa. Simple tuners use variable capacitors and inductors; the operator adjusts them by hand while
observing reflected power on the SWR meter until a minimum SWR is reached. The LDG
Electronics KT-100 automates this process.
No tuner will fix a bad antenna. If the antenna is far from resonance, the inefficiencies inherent
in such operation are inescapable; it’s simple physics. Much of the transmitted power may be
dissipated in the tuner as heat, never reaching the antenna at all. A tuner simply “fools” the
transmitter into behaving as though the antenna were resonant, avoiding any damage that might
otherwise be caused by high reflected power. For best performance, the antenna used should always
be as close to resonance as is practical.
THE LDG KT-100
In 1995, LDG Electronics pioneered a new type of automatic antenna tuner. The LDG design
uses banks of fixed capacitors and inductors, switched in and out of the circuit by relays under
microprocessor control. An additional relay switches between high and low impedance ranges. A
built-in SWR sensor provides feedback; the microprocessor searches the capacitor and inductor
banks, seeking the lowest possible SWR. The tuner is a “Switched L” network, consisting of series
inductors and parallel capacitors. LDG chose the L network for its minimum number of parts and
its ability to tune unbalanced loads, such as coax-fed dipoles, verticals, Yagis, and, in fact, virtually
any coax-fed antenna.
The series inductors are switched in and
out of the circuit, and the parallel capacitors
are switched to ground under
microprocessor control. The high/low
impedance relay switches the capacitor bank
either to the transmitter side of the inductor
bank, or to the antenna side. This allows the
KT-100 to handle loads that are either
greater than or less than 50 ohms. All relays
are sized to carry 125 watts continuously.
The SWR sensor is a variation of the
Bruene circuit. This SWR measuring
technique is used in most dual-meter and
18 37.97 7.87 5.08 4.00 3.42 3.06 2.80 2.62 2.47
50
20
22
24
26
28
30
32
34
36
38
40
42
44
46
9.90 5.83 4.44 3.73 3.30 3.00 2.78 2.62
12.92 6.74 4.94 4.07 3.55 3.21 2.96 2.77
17.94 7.87 5.51 4.44 3.83 3.42 3.14 2.92
27.96 9.32 6.17 4.85 4.12 3.65 3.32 3.08
57.98 11.24 6.95 5.31 4.44 3.90 3.52 3.25
13.93 7.87 5.83 4.79 4.16 3.73 3.42
17.94 9.00 6.42 5.18 4.44 3.95 3.60
24.63 10.40 7.09 5.60 4.75 4.19 3.80
37.97 12.20 7.87 6.07 5.08 4.44 4.00
77.99 14.60 8.80 6.60 5.44 4.71 4.21
21.95 11.92 8.55 6.85 5.83
17.94 9.90 7.19 5.83 5.00 4.44
22.96 11.24 7.87 6.26 5.31 4.68
31.30 12.92 8.65 6.74 5.65 4.94
47.98 15.08 9.56 7.27 6.02 5.22
direct-reading SWR meters. Slight
PAGE 18
modifications were made to the circuit to provide voltages instead of currents for the analog-todigital converters that provide signals proportional to the forward and reflected power levels. The
single-lead primary through the center of the sensor transformer provides RF current sampling.
Diodes rectify the sample and provide a DC voltage proportional to RF power. These two voltages
are read by the ADCs in the microprocessor, and are used to compute SWR in real time.
The relays are powered by the 12VDC input provided by the radio interface cable. This power is
supplied by the transceiver itself. The relays are a latching type, and so they consume no current
when not actively switching.
Although the microprocessor’s oscillator runs at 8 MHz, which allows the main tuning routine
to execute in only a few milliseconds, the relays require several milliseconds of settling time for every
combination of inductors and capacitors. Thus, it may take several seconds before all relay
combinations are exhausted, in the case of a difficult tune.
The tuning routine uses an algorithm to minimize the number of tuner adjustments. The routine
first de-energizes the high/low impedance relay if necessary, then individually steps through the
inductors to find a coarse match. With the best inductor selected, the tuner then steps through the
individual capacitors to find the best coarse match. If no match is found, the routine repeats the
coarse tuning with the high/low impedance relay energized. The routine then fine tunes the
inductors and capacitors. The program checks LC combinations to see if a 1.5:1 or lower SWR can
be obtained, and stops when it finds a good match.
The microprocessor runs a fine tune routine just after the tuner finds a match of 1.5:1 or less.
This fine tune routine now tries to the the SWR as low as possible (not just to 1.5); it takes about
half a second to run.
A WORD ABOUT TUNING ETIQUETTE
Be sure to use a vacant frequency when tuning. With today’s crowded ham bands, this is often
difficult. However, causing interference to other hams should be avoided as much as possible. The
KT-100’s very short tuning cycle, as little as a fraction of a second, minimizes the impact of tuning
transmissions.
CARE AND MAINTENANCE
The KT-100 tuner is essentially maintenance-free. Power limits in this manual should be strictly
adhered to. The outer case may be cleaned as needed with a soft cloth slightly dampened with
household cleaning solution. As with any modern electronic device, the KT-100 can be damaged by
temperature extremes, water, impact, or static discharge. LDG strongly recommends the use of a
good quality, properly installed lightning arrestor in the antenna lead.
TECHNICAL SUPPORT
The LDG Customer Support Center staff is ready to answer your product question by telephone
and over the Internet. We know that you will enjoy your product even more knowing LDG is ready
to answer your questions as the need arises.
Visit the Support Center at:
http://support.ldgelectronics.com
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Our website links you to the on-line Customer Support Center where you can send us a
question, do your own research in the LDG Product Knowledge Books, and read through lists of
frequently asked product questions. LDG regularly updates on-line information so the best on-line
support information is available all day and every day.
The LDG website provides links to product manuals, just in case you lose this one! When you
are thinking about the purchase of other LDG products our website also has complete product
specifications and photographs you can use to help make your purchase decision. Don’t forget the
links to all of the quality LDG Dealers also ready to help you make that purchase decision.
TWO-YEAR TRANSFERRABLE WARRANTY
Your product is warranted against manufacturer defects in parts and labor for two full years
from the date of purchase. This two-year warranty is also transferable. When you sell or give away
your LDG product give the new owner a copy of the original sales receipt and the two-year warranty
goes with the new owner.
There is no need to complete a warranty card or to register an LDG product. Your product
receipt establishes eligibility for warranty service so save that receipt. Send your receipt with the
product whenever you send your product to LDG for repair. Products sent to LDG without a
receipt are considered requests for out-of-warranty repair.
LDG does not warranty against product damage or abuse. This means that a product failure, as
determined by LDG, to be caused by the customer or by other natural calamity (e.g. lightning) is not
covered under the two-year warranty. Damage can be caused by failure to heed the product’s
published limitations and specifications or by not following good Amateur practice.
OUT OF WARRANTY SERVICE
Any time a product fails after the warranty, LDG wants to help you get it fixed. Send the
product to us for repair. We will determine what needs to be done, and, based on your prior
instruction, either contact you with an estimate or fix it and contact you with a request to pay any
repair charges. Please contact LDG if you have any questions before you send us an out-of-warranty
product for repair.
RETURNING YOUR PRODUCT FOR SERVICE
Returning a product to LDG is easy. We do not require a return merchandise authorization.
Visit the Customer Support Center and download the LDG Product Repair Form. On the Repair
Form tell the LDG technicians exactly what happened or didn’t happen and why you believe the
product needs servicing. The technician attempts to duplicate the problem(s) you had based on how
well you describe it so take the time to be accurate and complete.
Ask your shipper for a tracking number or a delivery verification receipt. This way you know the
product arrived safely at LDG. Be sure to give us your email address so our shipper can alert you
online when your product is en-route back to you. We regret that we are not staffed to provide
periodic updates on the status of repairs. We can only indicate the repair is in process until it ships
back to you. Please be assured that our staff makes every effort to complete repairs ahead of our
published wait time. Your patience is appreciated.
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Repairs can take six to eight weeks, but are usually faster than this. The most recent information
on returning products for service is found at the LDG Customer Support Center.
PAGE 21
Mail your carefully packaged repair with the Repair Form to:
LDG Electronics, Inc.
Attn: Repair Department
1445 Parran Rd
St. Leonard, MD 20685
PRODUCT FEEDBACK
We encourage product feedback! Tell us what you really think of your LDG product. In a card,
letter, or email (preferred) tell us how you used the product and how well it worked in your
application. Send along a photo or even a schematic or drawing to illustrate your narrative. We like
to share your comments with our staff, our dealers, and even other customers at the LDG website.
http://www.ldgelectronics.com/
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