LDG AT-1000 1KW
Automatic Memory
Antenna Tuner
LDG Electronics
1445 Parran Road, PO Box 48
St. Leonard MD 20685-2903 USA
Phone: 410-586-2177
Fax: 410-586-8475
ldg@ldgelectronics.com
www.ldgelectronics.com
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LDG AT-1000 1KW Automatic Antenna Tuner
Table of Contents
Introduction 2
IMPORTANT SAFETY WARNINGS 2
Jumpstart, or
Specifications 3
Operating Instructions
Getting to know your AT-1000 4
Installation 5
Operation 6
Theory of Operation
Some basic ideas about impedance 10
Transmitters, transmission lines, antennas and impedance 10
The LDG AT-1000 11
Care and Maintenance
Technical Support 14
Warranty and Service 14
Firmware upgrades
Feedback
Introduction
Congratulations on selecting the LDG AT-1000 tuner. The AT-1000 is a breakthrough product, providing
fully automatic antenna tuning with memories 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 energy within its specifications, with a reasonable margin of safety.
However, some amateur amplifiers are capable of outputting RF levels in excess, sometimes far in 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.
“Real hams don’t read manuals!” 3
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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 pilot will flash once. Press the Power button to turn on the tuner.
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. Transmit a carrier from your exciter
5. 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.
6. Tune your amplifier if needed; you’re ready to transmit.
of 20 watts CW, FM or AM.
Specifications
• Microprocessor controlled
• 200 non-volatile memories
• Switched L tuning network
• Back-lit cross needle meters
• Continuous coverage 1.8 to 54 MHz
• Power rating HF (1.8 to 30 MHz):
• 1000 Watts Single Side Band
• 750 Watts CW
• 500 Watts Digital (RTTY, Packet, etc.)
• Power rating 6 meters:
• 100 Watts
• Capacitor / Inductor fine tune controls
• Tuning time: 1 to 8 seconds, 4 average. Memory tune time: less than 0.5 seconds.
• Antenna impedance: 6 to 800 Ohms (approximately up to 10:1 SWR)
• Tuning power: 20 to 125 watts maximum, constant carrier
• Relay protection software prevents tuning:
• Greater than 125 watts into a 1:1 SWR load
• Greater than 75 watts into a 3:1 SWR load
• Soft touch buttons
• Includes 6 foot power cable
• Power requirements: 11 to 15 volts DC @ 1 Amp (user supplies power source)
• Enclosure sizes: 9 x 13 x 3 (measured in inches)
• Weight: 6 pounds
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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 (rarely needed)
• Ind Up: adds inductance
• Ind Dn: subtracts inductance
• Cap Up: adds capacity
• Cap Dn: subtracts capacity
• Tune: begins a tuning cycle, places the tuner in bypass mode
The Power switch does not turn the tuner completely off. It places it in a low-current “sleep” mode. In the
Off mode, the tuner is in bypass, routing RF directly from your amplifier to the antenna with no matching.
On power-up, 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.
In addition to the pushbuttons, there is 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 forward power of 100 watts, reflected power of 11 watts and an SWR of 2.0.
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On the back panel, there are four connectors:
• DC power input (2.5 x 5.5 mm coaxial power connector, center pin positive)
• RF in (marked “Transmitter”, standard SO-239 socket)
• RF out (marked “Antenna”, 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
provided 2.5 x 5.5 mm coaxial power plug. Be sure to observe proper polarity; the center pin, and the red
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