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Kessler Engineering, LLC
P.O. Box 341543
Beavercreek, Ohio 45434

Tel: 937.458.3173

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Amateur Radio Tuners

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AT Auto Tuner. Click to view larger image.

The AT-AUTO is a fully autonomous, fully automatic impedance matching network (an antenna tuner) that employs an embedded microprocessor to position a conventional roller inductor and a split-stator variable capacitor. It provides continuous coverage tuning from 1.8 - 54 MHz (including MARS, DoD, and commercial frequency bands, etc.) and is rated for 1500 W continuous carrier operation. The AT-AUTO is quiet and reliable, and with its industrial-rated stepper motors, provides a superior impedance match to that provided by the loud clanking boxes of relays provided by the competitors.

The AT-AUTO continuously measures forward and reflected RF power. As long as the SWR is below a user-selectable threshold, the AT-AUTO provides a "Good Match" cue in the Liquid Crystal Display (LCD) and takes no further action. Whenever the SWR exceeds the "Tune-Start" SWR, the AT-AUTO then counts the RF carrier frequency, looks up previously stored Inductor (L) and Capacitor (C) settings for the frequency of operation and then repositions L & C to the recalled settings. If the SWR is still excessive, the AT-AUTO automatically begins tuning, and provides user prompts during the entire process via the LCD. Once a good match is found, the new match settings are stored in memory for subsequent recall. The default behavior is highly customizable to suit individual needs.

The AT-AUTO is also able to obtain frequency information via the radio's serial data port (for these compatible radios so equipped). By doing so, the AT-AUTO instantly follows frequency changes (VFO adjustment, etc.) and immediately recalls and sets the L & C for the new frequency - without the need to generate an RF carrier! The recalled match should provide an excellent SWR so that when RF is finally applied, subsequent tuning will not be necessary. While the serial port is not necessary for automatic tuning, this "Smart Mode" of operation greatly speeds the entire process of changing frequencies.

Note: The AT-AUTO is currently not in production and not available for sale. It is undergoing a redesign for release soon. The pictures and descriptions shown here are of the existing version(s) of the AT-AUTO tuner prior to its production cessation.

A new web page for the AT-AUTO II is coming soon!

    AT-Auto Tuner Cables

    The AT-AUTO sends and receives serial data to/from the associated radio via the radio's serial port. This is commonly referred to as Computer Aided Tuning or CAT. In order for the radio and the AT-AUTO to be able to communicate serially, an appropriate CAT cable must be used.

    Because there is no defacto standard for CAT, there are variations in connectors and pin assignments from manufacturer to manufacturer. Therefore, there are unique AT-AUTO CAT cables for Elecraft, Kenwood, TenTec, Yaesu, and others. The CAT cables themselves are nearly identical, with minor variations in the specific connector and pin assignments.

    ICOM has their own CAT implementation known as CI-V which uses entirely different protocols. ICOM radios, therefore, do not use the CAT cable, but instead use a CI-V cable.

    Cable Sets consist of a Firmware Update Cable, A CAT/CI-V Cable, and in the case of some Kenwood radios, a Tuner-Handshake Cable. Schematic diagrams of the various cables are provided in the AT-AUTO user manual.

    Purchase Cables for the AT-Auto Tuner

    PhotoDescriptionPrice eachPurchase
    "Universal Serial Interface" for the AT-AUTO. It comes supplied with three identical serial cables and the interface board. The universal interface eliminates the need for different radio-specific cables and only uses typical 9-pin serial cables. The interface has three switches that permit quick selection of mode as well as radio-specific settings. This is the best option for your situation and it less expensive than buying multiple sets of cables. A PDF manual is available here.$58.00
    ICOM Interface Cable Set, 6 feet long. The Icom Tuner-Handshake is much simpler to implement with no special circuit boards required. This feature is incorporated into the ICOM CI-V cable.$40.00
    Firmware Update Cable, 6 feet long. The AT-AUTO employs a microprocessor and the programming (firmware) may be updated by the user as new features and improvements are made. This requires a standard 9-pin male-to-female serial cable, which we refer to as the Firmware Update Cable.$7.50
    Elecraft Serial Data Interface Cable Set, 6 feet long$30.00
    TenTec Serial Data Interface Cable Set, 6 feet long$30.00
    Kenwood/Yaesu Serial Data Interface Cable Set, 6 feet long$30.00
    New! AT-AUTO Power Cable$28.00

    AT-Auto Tuner Upgrades

    Although currently out of production, we are dedicated to providing outstanding product support for the legacy AT-AUTO tuner. Until now, that product support has consisted primarily of repair and firmware updates. However, in to ensure AT-AUTO operational longevity and to prevent product obsolescence, we are in the process of developing a series of hardware improvements for the legacy AT-AUTO.

    As those hardware improvements occur, they will be made available to AT-AUTO owners.

    One of the most common complaint areas concerns the AT-AUTO's stock meter. Meter problem areas have been "sticking" needle movements due to static electricity accumulation, illumination "hot spots" and difficulty obtaining replacement incandescent meter lamps. Other complaints involve meter face clutter and lack of resolution.

    In order to solve the meter issues, we developed a replacement meter using better plastics that prevents the static electricity build-up and is back-lit with three LEDs, providing nearly uniform illumination and eliminating the incandescent lamp burnout/replacement issues.

    Purchase AT-Auto Tuner Upgrades

    PhotoDescriptionPrice eachPurchase
    New! AT-AUTO Replacement Meter Kit$53.00

    AT-AUTO Replacement Meter Kit Manual

    The manual is available as a downloadable PDF here: AT-AUTO Meter Upgrade Kit Manual.

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