LDG AT-1000 User manual

AT
-
1000
Automatic Antenna Tuner
Manual
Version 1.0G
LDG Electronics
1445 Parran Road, PO Box 48
St. Leonard MD 20685-2903 USA
Phone: [phone] Fax: [phone]
[email protected] www.ldgelectronics.com

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LDG AT-1000 1KW Automatic Antenna Tuner
Table of Contents
Introduction 1
IMPORTANT SAFETY WARNINGS 1
Jumpstart, or “Real hams don’t read manuals!” 2
Features 2
Specifications 2
Operating Instructions 3
Getting to know your AT-1000 3
Installation 4
Basic Operating Instructions 5
Advanced Operating Instructions 5
Troubleshooting and FAQ 7
Theory of Operation 8
Some basic ideas about impedance 8
Transmitters, transmission lines, antennas and impedance 8
The LDG AT-1000 10
Care and Maintenance 12
Technical Support 12
Warranty and Service 12
Firmware upgrades 12
Feedback 13
Introduction
Congratulations on selecting the LDG AT-1000 tuner. The AT-1000 is a breakthrough product, providing
fully automatic antenna tuning for high power amplifiers. The AT-1000 is intended for use with most tube
or transistor amplifiers outputting up to 1,000 watts SSB. It will tune dipoles, verticals, Yagis or virtually
any coax-fed antenna.
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 for
every amateur need.
IMPORTANT SAFETY WARNINGS
Like all high power antenna tuners, your AT-1000 handles a great deal of RF energy. Very large RF
currents flow through the tuner, and very high RF voltages are sometimes present. Your AT-1000 is
designed to safely handle this RF power within its specifications,with a reasonable margin of safety.
However, some amateur amplifiers are capable of outputting RF levels in excess, sometimesfarin excess,
of the specified maximums. Operating significantly above specifications will definitely damage or destroy
your AT-1000. Operating above specifications can cause catastrophic failure of internal components; under
extreme overload, components could actually explode. You must observe the stated specifications of your
AT-1000, just as you do with your amplifier or any conventional tuner operating at this power level. Never
operate your AT-1000 with the cover removed; lethal RF voltages may be present during operation.

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Jumpstart, or “Real hams don’t read manuals!”
Ok, but at least read this one section before you transmit:
Safety Warning: Never operate your AT-1000 with the cover removed; lethal RF voltages may be present
during operation. Never exceed specifications.
1. Connect your AT-1000 to a source of 11 –15-volt DC power capable of supplying at least 1 Amp, red
lead positive. The tuner will automatically power up; pilot and meter lights will come on.
2. Connect your amplifier output to the AT-1000 input socket labeled “Transmitter” using 50-ohm
coaxial cables. Connect the coax lead to your antenna to the AT-1000 output socket labeled
“Antenna”.
3. Set your amplifier to “Standby” mode so it will NOT operate when you transmit.
4. If your AT-1000 is off, press “Power” to power up.
5. Transmit a carrier from your exciterof 20 watts CW, FM or AM.
6. Momentarily press the “Tune” button on your AT-1000. An automatic tuning cycle will begin, then
stop. Check the meter to ensure an SWR of 2 or less before using your amplifier.
7. Tune your amplifier if needed; you’re ready to transmit.
Features
•Automatically matches antennas from 6 –800 ohms impedance, or a 10:1 SWR
•Handles 1000 watts output on SSB, 750 watts CW and 500 watts on FM, digital or other 100%
duty cycle modes
•Tunes in less than 10 seconds, usually less than 5 seconds
•Retains last tuned setting as long as DC power is connected
Specifications
•Impedance range: 6 –800 ohms, or SWR up to 10:1
•Minimum power for tuning: 20 watts
•Maximum power while tuning: 100 watts with rollback, 20 watts without rollback (see section on
rollback)
•RF power limits: 1,000 watts SSB, 750 wattsCW, 500 watts “key down”, FM, digital or any other
100 % duty cycle mode
•Meter accuracy: +/-5% of full scale across entire range
•DC power requirement: 11 –15 volts DC, 2.5 x 5.5 mm coaxial plug, center pin (red lead) positive
•Current consumption: 1 Amp or less
•Dimensions: 9” wide, 3 ½” high, 13 inches deep (not including connectors)
•Weight: 5 lbs. 4 oz.

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Operating Instructions
Getting to know your AT-1000
Your AT-1000 is a quality, precision instrument that will give you many years of outstanding service; take
a few minutes to get to know it. On the front panel, there are six pushbutton switches:
•Power: turns your AT-1000 on and off
•Manual capacity and inductance adjustments (if needed)
•Ind Up: increases inductance
•Ind Dn: decreases inductance
•Cap Up: increases capacity
•Cap Dn: decreases capacity
•Tune: begins an automatic tuning cycle
The Power switch does not turn the tuner completely off. It places it in a low-current “sleep” mode that
retains the last tuned setting, providing DC power remains connected. When turning on with power button,
the tuner is automatically restored to the last tuned setting. If DC power is interrupted, the tuner will revert
to bypass mode on power-up. The Cap Dn and Ind Dn buttons are also used in combination to place the
tuner in “bypass” mode, as described later in this section.
In addition to the pushbuttons, there is backlit a cross-needle meter. This meter indicates forward power up
to 1,000 watts, reflected power up to 180 watts and SWR (see Theory of Operation, below). Power readings
are accurate to +/-5% of full scale across the entire range (this may very well be the most accurate
wattmeter you own!). This meter also indicates various operational states, as described later in this section.
Forward and reflected power are indicted on individual scales. SWR is read at the intersection of the two
needles, on the curved red scales across the center of the meter face. In the picture below, the meter is
indicating an SWR of 2.0.

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On the back panel, there are fourconnectors:
•DC power input (2.5 x 5.5 mm coaxial power connector, center pin positive)
•RF in (standard SO-239 socket)
•RF out (standard SO-239 socket)
•Ground (wingnut)
“What’s the deal with the hole?” Sharp-eyed users will note an empty cutout labeled “Control” on the back
panel. Future versions of the AT-1000 may feature remote control and monitoring via a DB-9 connector in
this position. This feature may also be offered as an upgrade for present users, but is not available at this
time. In this version, the cutout serves no function. Never insert anything into this cutout, especially when
transmitting.
Installation
Your AT-1000 is intended for indoor use only; it is not water-resistant. If you use it outdoors (Field Day,
for example) you must protect it from rain. Place your AT-1000 as near as practical to your exciter (your
transceiver or transmitter) and your amplifier, keeping free access to the front panel controls. You should
avoid placing other equipment on top of your AT-1000 if possible to aid in cooling.
Grounding will significantly improve the safety and performance of your tuner. Attach the ground
connection on the back panel to a suitable ground using heavy-gauge wire or metal braid. A dedicated
outside ground rod is best, but a nearby cold water pipe is usually satisfactory. If no other ground is
available, the screw holding the cover on a power outlet is a usable ground.
Connect the socket marked “Transmitter” on the back of your AT-1000 to your amplifier output using
high-quality 50-ohm coaxial cable and PL-259 plugs. Do not use crimp-on plugs for this connection; only
properly soldered plugs will be safe and provide satisfactory performance. The coaxial cable should be
rated for the maximum output of your amplifier. Keep the cable as short as practical.
Attach your antenna lead-in coax to the socket marked “Antenna” on the rear of the tuner with a soldered
PL-259 plug. Your AT-1000 is intended for use with coax-fed (unbalanced) antennas only. If you wish to
use it with antennas fed with ladder-line, or with longwire antennas you must provide a suitable balun to
adapt your AT-1000 to the balanced load. LDG does not presently sell a balun that handles 1,000 watts, but
they are readily available from many ham radio vendors.
Your AT-1000 requires 11 –15 volts DC at 1 Amp. If your exciter runs on 12 volts DC, you can use the
same power supply for your AT-1000 if it can provide the necessary 1 Amp current; otherwise, you will
need a separate power supply. We recommend a regulated supply, but an unregulated one may be used with
satisfactory results. Connect the power supply to the DC power jack on the back of your AT-1000 using the

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provided 2.5 x 5.5 mm coaxial power plug. Be sure to observe proper polarity; the center pin, and the red
lead are positive.
Basic Operating Instructions
Press the “Power” button on the front panel. The red LED above the button, and the meter lights come on
indicating that your AT-1000 has powered up and successfully completed a self-test. The tuner is now
ready to use.
Set your amplifier to standby, so it will not operate when you transmit; tune with your exciter only. Set
your exciter to transmit 20 watts (without rollback; see below), or up to 100 watts (with rollback) on the
frequency you plan to use. CW is usually the most convenient mode, but you can also use FM or an AM
carrier.
While transmitting 20 –100 watts, momentarily press the “Tune” button on the tuner front panel; an
automatic tuning cycle will begin. You will hear the relays in your AT-1000 operate as they switch
inductors and capacitors in and out seeking a match; they make a fairly loud buzzing noise. You can
observe the present reflected power and SWR on the meter during the tuning process—but watch closely; it
happens fast! The tuning cycle will automatically end in a few seconds, with the meter indicating the final
achieved SWR, usually 1.5 or less. Check for an SWR of 2 or less. If the SWR is greater than 2, use the
manual adjustment buttons to adjust the SWR to level less than 2. Unkey your exciter.
Set your amplifier to operate, key your exciter and tune your amplifier as usual (if needed). Good practice
dictates tuning your amplifier into a 50-ohm dummy load with a suitable power rating. You may tune your
amplifier into the antenna through your AT-1000 providing it has tuned the antenna to a low SWR, and also
providing you do not exceed the specified ratings of either your amplifier or your AT-1000. Never press the
Tune button while transmitting more than 100 watts. Unkey when done; you are ready to transmit.
A word about “roll-back” circuits
Modern amateur exciters with solid state finals usually employ a “rollback” circuit to protect the final
amplifier transistors from high SWR, which can damage or destroy them. A rollback circuitsenses the
SWR at the antenna terminal during transmit, and reduces the output power as the SWR rises above a
preset level, often 2:1. The higher the SWR, the lower the power is set to prevent damage.
If your solid state or tube-type exciter has a rollback circuit, you can simply key down and tune as
described above at any power level from 20 to 100 watts. If your exciter lacks a rollback circuit, you must
manually set the power level for tuning to 20 watts. At higher power levels, the reflected power
encountered during the tuning cycle could damage your exciter. Check your exciter owner’s manual to
determine if yours has a rollback circuit. Note that most Ten-Tec radios do not have rollback circuits.
Advanced Operating Instructions
Fine-tuning the tuner
In rare circumstances, the automatic tuning cycle will end with a relative high SWR, perhaps 1.5 or 2. This
is usually due to operation far from the antenna’s natural resonant frequency. You can manually adjust the
match using the Ind and Cap Up and Dn buttons on the front panel. While still transmitting with your
exciter after the automatic tuning cycle ends, you can press these buttons and observe the effect on SWR on
the meter.
Since you don’t know how the automatic tuning cycle set the inductors and capacitors, you will have to
make manual adjustments by trial and error. Press the Cap or Ind Up button three times and observe the
change in SWR. If it gets worse, tap the Dn button three times to return to your starting place, then try three

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taps of the Dn button. Once you’ve gone through this process a few times, you will get a better feel for
matching certain antennas or frequencies.
Advanced controls
Pressing the “Cap Dn” and “Ind Dn” buttons together places the tuner in bypass mode. RF from your
amplifier goes directly to the antenna with no matching.
Meter bounce codes
In addition to displaying power and SWR, the power meter also indicates several important tuner states.
The meters are used as a kind of digital output device; they “bounce” to indicate information. While
bouncing, they do not indicate power levels.
There are three levels of bounce (100, 300 and 1,000 watt marks on the forward power meter) and two
speeds (fast and slow). For example, when you press [Ind Dn + Cap Dn] to place the tuner into bypass, the
meter bounces to the 100 watt mark at the slow rate until you release the buttons. The following table
shows the various meter bounce codes:
Meter Bounce Codes 100 Watt Mark 300 Watt Mark 1000 Watt Mark
Slow Rate Bypass Mode Not used Power > 75 watts and
SWR > 3
Fast Rate Manual Adjustment
(Cap or Ind) at Limit Insufficient Power to Tune Power Too High to Tune (>125 watts)
The two 1000 watt mark bounce codes indicate that your AT-1000 has activated a self-protection mode.
The tuner will not allow you to change any tuner setting if the input power exceeds 75 watts when the SWR
is greater than 3, or when the input power exceeds 125 watts regardless of SWR. If you press the Tune
button under these conditions, the tuner will not begin a tuning cycle, but will indicate the appropriate
bounce code on the meter. When this happens, unkey your exciter, reduce power and start a new tuning
cycle. Never purposely test these two codes by attempting to tune with too much power; these are safety
features to help prevent damage to your tuner.
AT
-
1000 Quick Reference Card
Maximum power when tuning: 100 watts with rollback, 20 watts without rollback
Maximum power: 1,000 watts SSB, 750 watts CW, 500 Watts continuous
“Power” turns tuner on, or places it in “sleep mode”, retaining last tuned setting
To start a tuning cycle: momentarily press the “Tune” button
To fine tune match, use “Cap” and “Ind” Up and Dn buttons
To place tuner in Bypass mode momentarily press ”Cap Dn” and “Ind Dn” together
Principal meter bounce codes:
Slow-100W: Bypass mode Fast-100W: Manual adjustment at limit
Fast-300W: Insufficient power to tune Fast/Slow-1000W: self-protect modes
Quick Reference Card: copy, cut out and laminate

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Troubleshooting and FAQ:
My tuner will not tune on one band
Your coax length may be an odd ¼ wavelength of the frequency that you are trying to tune. Lengthen your
coax 3 to 6 feet (1 to 2 meters).
My tuner will not tune on many bands and the meters exhibit erratic behavior
You may have RF getting into the tuner via the power cable. Install a choke on the power cable. Radio
Shack sells snap-on chokes which are easy to install. Simply wrap the power cord around the choke as
many times as it will fit and snap it shut. This can also be a problem with your antenna system. Attaching a
dummy load at the antenna feed point can be a useful tool in checking your feed line and associated
connectors. Be sure you knowthe rating of your coax, balun, etc. for the power you are using.
This can also point to a shack / antenna / ground problem and can be a bear to find. Each unit to be
grounded (i.e. radio, tuner, amplifier, or widget) must be run individually to earth ground, not “daisy-
chained”. Please refer to the ARRL Handbook for guidance on grounding systems
If the RF power is reduced on your radio and the problem goes away, this usually indicates RF presence in
the shack.
My tuner doesn’t tune when I hold the Microphone button in SSB
The tuner requires a constant carrier to tune. SSB only provides RF power when intelligence is being
transmitted (i.e. voice modulation). Use AM, FM, or CW for tuning.
My tuner sounds like “marbles in a blender” when it tunes
Yes,it does! Those are the relays switching 30 times per second and do make a bit of noise. This is normal
operation. If you hear any relays click during transmit (after tuning) this indicates a possible problem.
Reduce power and see if the problem goes away. This can indicate RF in the shack.
Why do I have to touch up the match found by the tuner?
If the SWR is less than 2:1, you don’t have to, but we recommend it. The microprocessor inside your tuner
is a very sensitive device. It can perceive the smallest of variations in SWR. The microprocessor, because it
is so sensitive, can also be fooled due to RF feedback or the presence of RF in the shack and cause the
lowest SWR to missed by a little bit. A few button clicks will normally touch up the match. Being familiar
with your tuners operation and tuning capabilities helps you identify if problems develop in your antenna
system.
Can I use this tuner when I am just running 100 Watts?
Yes! The tuner will tune and operate from 20 to 100 watts.
Why can’t I tune using my amplifier?
The extremely high voltages associated with high power combined with high SWR will arc the relays and
destroy them. When the relays are settled, the contacts are rated to handle voltages and current associated
with a 2:1 SWR or lessto the tuners specified rating by mode.
Why shouldn’t I operate the tuner if the match found is higher than 2:1 SWR?
The relays are rated for the voltages and current present in a 2:1 SWR load for the tuners rating by mode.
Operating outside the 2:1 SWR can and will burn relays. This tuner has been tested and tested and tested
again; it will perform well within specs for a long, long time. You can burn this tuner up with improper
operation!

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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” parts1. It is beyond the
scope of this manual to present a tutorial on this subject, but a little background will help you understand
what your AT-1000 is doing, and how it does it.
In simple DC circuits, the wire resists the 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 Sir George Simon Ohm of England, who first described it in 1826. In RF circuits, an analogous but far
more complicated relationship exists.
RF circuits also resist the flow of electricity. However, the presence of capacitive and inductive elements
cause the voltage in the circuit to lead or lag the current, respectively. In RF circuits this resistance to the
flow of electricity is called “impedance”, and can include all three elements: resistive, capacitive, and
inductive.
The output circuit of your amplifier 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 your amplifier, the transmission line, and the antenna all have a characteristic
impedance. For reasons too complicated to go into here, the standard impedance is about 50 ohms resistive,
with zero capacitive and 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 amplifier to the
antenna occurs. While the output circuit and transmission line are of fixed, carefully designed impedance,
the antenna presents a 50 ohm, non-reactive load only at its natural resonant frequencies. At other
frequencies, it will exhibit capacitive or inductive reactance, causing it to have an impedance different from
50 ohms.
When the impedance of the antenna is different from that of the amplifier and transmission line, a
“mismatch” is said to exist. In this case, some of the RF energy from the amplifier is reflected from the
antenna back down the transmission line, and into the amplifier. If this reflected energy is strong enough it
can damage the amplifier’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 rises to 2, 3 or
higher. As a general rule, modern solid state amplifiers must operate with an SWR of 3 or less. Tube
exciters are more tolerant of high SWR. If your 50 ohm antenna is resonant at your operating frequency, it
will show an SWR of 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.
1For a very complete treatment of this subject, see any edition of the ARRL Radio Amateur’s Handbook
Inductive
Reactance
Capacitive
Reactance

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FR
FR
SWR /1
/1− +
=
SWR is measured using a device called an “SWR bridge”, inserted in the transmission line between the
amplifier and antenna. This circuit measures forward and reverse power from which SWR may be
calculated (some meters calculate SWR for you). More advanced units can measure forward and reverse
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. Tuners add capacitance to
cancel out inductive reactance in the antenna, and vice versa. Simple tuners use variable capacitors and
inductors. The operator adjusts the them by hand while observing reflected power on the SWR meter until a
minimum SWR is reached. Your LDG AT-1000 automates this process.
No tuner will fix a bad antenna. If your antenna is far from resonance, the inefficiencies inherent in such
operation are inescapable; it’s simple physics. Much of your transmitted power may be dissipated as heat in
the tuner, never reaching the antenna at all. A tuner simply “fools” your amplifier into behaving as though
the antenna were resonant, avoiding any damage that might otherwise be caused by high reflected power.
Your antenna should always be as close to resonance as practical.
where F = Forward power (watts), R = Reflected power (watts)
SWR Lookup Table
Find SWR at intersection of
forward power column and
reflected power row.
Forward Power (Watts)
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
42.62 2.15 1.92 1.79 1.70 1.63 1.58 1.53 1.50
63.42 2.62 2.26 2.06 1.92 1.83 1.75 1.70 1.65
84.44 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
16 17.94 6.42 4.44 3.60 3.14 2.83 2.62 2.46 2.33
18 37.97 7.87 5.08 4.00 3.42 3.06 2.80 2.62 2.47
20 -9.90 5.83 4.44 3.73 3.30 3.00 2.78 2.62
22 -12.92 6.74 4.94 4.07 3.55 3.21 2.96 2.77
24
-
17.94
7.87
5.51
4.44
3.83
3.42
3.14
2.92
26 -27.96 9.32 6.17 4.85 4.12 3.65 3.32 3.08
28 -57.98 11.24 6.95 5.31 4.44 3.90 3.52 3.25
30 - - 13.93 7.87 5.83 4.79 4.16 3.73 3.42
32 - - 17.94 9.00 6.42 5.18 4.44 3.95 3.60
34
-
-
24.63
10.40
7.09
5.60
4.75
4.19
3.80
36
-
-
37.97
12.20
7.87
6.07
5.08
4.44
4.00
38 - - 77.99 14.60 8.80 6.60 5.44 4.71 4.21
40 - - - 17.94 9.90 7.19 5.83 5.00 4.44
42 - - - 22.96 11.24 7.87 6.26 5.31 4.68
44 - - - 31.30 12.92 8.65 6.74 5.65 4.94
46
-
-
-
47.98
15.08
9.56
7.27
6.02
5.22
48 - - - 97.99 17.94 10.63 7.87 6.42 5.51
50 - - - - 21.95 11.92 8.55 6.85 5.83
Reflected Power (Watts)

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The LDG AT-1000
In 1995 LDG 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. 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; in fact, virtually any coax-fed antenna. Using seven toroidal inductors, the total
inductance ranges from 0 to 10 µH. Each inductor’s value is selected to provide 128 different
combinations, with a resolution of 0.08 µH. The inductors are switched in and out of the circuit by relays
controlled by the microprocessor. An additional relay switches between high and low impedance ranges.
The inductors are wound with #16 wire on 2” toroid forms. Using seven 2,500 volt capacitors, the total
capacitance ranges from 0 to 650 pF. Each capacitor’s value is selected to provide 128 combinations, with a
resolution of 5 pF. The capacitors are connected to ground with the seven inductor relays. Another relay
switches the entire capacitor bank to the input or output side of the inductor. This switching allows the AT-
1000 to automatically handle loads that are greater than 50 ohms (high setting) and less than 50 (low
setting). All of the relays are SPDT types sized to handle up to 1,000 watts SSB (500 watts key down).
The SWR sensor is a variation of the Bruene circuit. This SWR measuring technique is used in most dual-
meter and direct-reading SWR meters. Slight modifications were made to the circuit to provide voltages
(instead of currents) for the analog-to-digital converters (ADCs) that provide signals proportional to the
forward and reverse 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. Variable resistors calibrate the FORWARD and REVERSE power levels. Once adjusted, the
forward and reverse power sensors produce a calibrated DC voltage proportional to the forward and reverse
RF power levels. These two voltages are read by the ADCs in the microprocessor. Once in a digital format,
the they are used to calculate SWR in real time.

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The relays operate from an external 12 volt DC power supply. The total current drawn by the AT-1000
depends primarily on the number of energized relays, with the maximum current drain being approximately
1 Amp.
Although the microprocessor’s oscillator runs at 8 MHz, its internal bus speed is on one-fourth that, or 2
MHz. This means that one instruction cycle executes in 0.9 ms. The main tuning routine takes about 75
cycles to make a tuner adjustment and take a new SWR measurement, or 67.5 ms per tuner adjustment. If
running at maximum speed, the microprocessor can try all inductor-capacitor combinations in just 8.8
seconds. Unfortunately, the mechanicalrelays can’t react as quickly as the microprocessor, and the tuning
speed must be slowed down to compensate for relay settling time.
The tuning routine, written in assembly language, 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 capacitors and
inductors. The program checks LC combination to see if a 1.5 or lower SWR can be obtained, and stops
when it finds a good match.
The number of tuner adjustments is between 4 and 288. There are 1 to 16 checks for the coarse inductor
tuning, 1 to 16 for the coarse capacitor and between 2 and 256 for the inductor and capacitor fine tuning.
With the speed reduced to 10 ms per selection to compensate for relay settling, the maximum tuning time is
6.1 seconds and the minimum tuning time is 0.06 second. Generally, the farther away from resonance an
antenna is from the exciter’s operating frequency, the longer it takes the tuner to find a match. Test results
show that a 40-meter half-wave dipole tunes to any frequency in the band in less than half a second.

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Care and Maintenance
Your AT-1000 tuner is essentially maintenance-free; just be sure to observe the power limits discussed in
this manual. The outer case may be cleaned as needed with a soft cloth slightly dampened in household
cleaning solution. As with any modern electronic device, your AT-1000 can be damaged by temperature
extremes, water, impact or static discharge. LDG strongly recommends that you ground your AT-1000, and
use a good quality, properly installed lightning arrestor in the antenna lead.
Technical Support
We are happy to help you with your AT-1000. Telephone technical support is available at410-586-2177
weekdays from 9 am to 5pm Eastern Time. Inquiries by Fax at 410-586-8475 are welcome, and prompt e-
mail support is available at [email protected].
Warranty and Service
Your AT-1000 is warranted against defects in parts or workmanship for one year from purchase. The
warranty does not cover damage due to abuse or exceeding specifications. This warranty applies to the
original purchaser only; it is not transferable. A copy of the receipt showing the purchaser’s name and the
date of purchasemust accompany units returned for warranty service. All returns must be shipped to us
pre-paid; we will not accept units with postage due. A return form is provided on our web site for your
convenience. Check the service page atwww.ldgelectronics.comfor the latest service information.
If you need to return your AT-1000 to us for service, package it carefully, keeping in mind that we will re-
use your packaging to return the unit to you. A self-addressed return-shipping label, while not required, will
help insure speedy and accurate delivery of your repaired unit. Include a full description of the problem,
along with your name, address and a phone number or e-mail address where we can reach you with any
questions. Repairs average about 3 to 6 weeks.
We will be glad to service your AT-1000 after the warranty period has ended. We will notify you of repair
charges by phone or e-mail, and bill you after repairs are completed.
Firmware upgrades
From time to time LDG may release upgraded firmware for the AT-1000, refining operation and adding
features. Your AT-1000 is not field programmable; you will have to remove the present chip and replace it
with the upgrade chip. To remove the chip you will need an appropriate tool. A PLCC extraction tool is
ideal, but if you don’t have one you can fashion a satisfactory substitute from an ordinary paperclip.
Straighten the paper clip, then bend it into a “U” shape. Use pliers to bend the last 1/8” of each end toward
the center (see illustration).

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The extraction tool fits into opposite corners of the 68HC11 socket; the bent ends will lift the chip from
beneath. Unplug the tuner, touch a ground point to avoid static discharge damage, and remove the cabinet
cover. Insert the tool and pull gently and evenly on both sides to extract the chip. Press the upgrade chip
into the socket, observing the small diagonal corner key. Replace the cabinet cover; your upgraded AT-
1000 is ready to use.
You will return the old processor chipto LDG; upgrades will be sold by exchange only. The processor
chips are recycled and reprogrammed to minimize future upgrade costs. Upgrades are expected to cost
about $10-$20 with chip exchange, and will be announced on our web site when available.
Feedback
If you have an idea to improve our software or hardware, please send us a description. If we incorporate
your idea in the AT-1000, we'll send you a free upgrade as a “thank you”.
We encourage everyone who uses the AT-1000 to contact us (card, letteror e-mail preferred) telling us
how well it works for you. We are also always looking for photographs of our products in use; we
frequently place such pictures on our Web site (www.ldgelectronics.com).