Kessler Engineering, LLC Amateur Radio and Custom RF Products

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

Tel: 937.458.3173

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Amateur Radio Products

Kessler Engineering, LLC's primary amateur radio products are automated antenna tuners, shack automation products, and associated accessories. The flagship of the Kessler Engineering LLC product line is the AT-AUTO, Automatic Antenna Tuner.

In 2005, Don Kessler began designing an automatically controlled impedance matching network (an antenna tuner). That design quickly evolved into the popular AT-AUTO antenna tuner. The AT-AUTO first went on sale at the 2006 Dayton Hamvention®.

Since then the AT-AUTO has matured and evolved in an attempt to satisfy the wishes of the growing customer base. During the past 5+ years, the AT-AUTO has become very highly sought after and has garnered a well-deserved reputation for its robustness, sophistication, and ease of use. Much of this is due to the fact that the AT-AUTO firmware is continually evolving, permitting addition of user-requested capabilities and new features.

While the AT-AUTO firmware has continued to evolve and mature, the AT-AUTO hardware had remained fundamentally unchanged from the first models that came off of the product line in early 2006. AT-AUTO product improvements have primarily been limited to updates and enhancements to the firmware, with only minor hardware changes. However, in order to keep the AT-AUTO relevant and competitive, we are now at the point where the hardware configuration may begin to hinder the ability to add several significant new (hardware) features. In short, it is time to dust off and update the AT-AUTO hardware design. For this reason, the AT-AUTO production is temporarily on-hold as we concentrate our efforts on the re-design of the AT-AUTO hardware.

A companion product to the AT-AUTO is the CX-AUTO. This was our solution to expanding the singular coaxial output available on the AT-AUTO. The CX-AUTO is an automatic coaxial antenna switch which is controlled by the AT-AUTO, giving the user the ability to use any one-of-eight coaxial-fed antennas with the AT-AUTO.

Custom RF Products

Kessler Engineering also provides electrical engineering consulting services, custom design of embedded control systems, unique RF product design, and electronic product fabrication. Dr. Kessler's expertise includes Power RF Electronics with an emphasis on Class-E RF amplifiers. Contact us directly for further details.

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Auto Tuner

The AT-AUTO satisfies the demands of the discerning ham for an automatically controlled antenna tuner. Unlike competing products with loud, clacking relays and burning relay contacts, the AT-AUTO uses stepper motors, under microprocessor control to precisely position a "real" roller inductor and a "real" air-dielectric variable capacitor. The AT-AUTO does not relay-switch discrete capacitors and inductors. Instead, it uses a continuously variable roller inductor and air-dielectric capacitor. As a result, the AT-AUTO provides superior impedance matching capability.

The AT-AUTO is a QRO automatic antenna tuner designed for 1.5kW CW operation. Unlike other "automatic" antenna tuners that require operator intervention, the AT-AUTO is fully autonomous - it will initiate auto tuning autonomously whenever the SWR warrants re-tuning.

By combining automation with a "conventional" differential-T impedance network, the AT-AUTO provides the impedance and power handling capabilities of a "conventional" manual tuner with the sophistication and automation afforded through the embedded microprocessor controller. As the user changes frequency, or hops from band-to-band, the AT-AUTO follows along automatically. The automation provided affords the operator time to enjoy hamming without the bother of manually retuning after each QSY.

The AT-AUTO is continuously evolving. New firmware features are developed and made available to existing AT-AUTO owners (for free). By using a convenient, easy to use Windows application, they may take advantage of the new firmware features by uploading the new firmware to their AT-AUTO(s).

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Coaxial Switch

The CX-AUTO coaxial switch features an embedded microprocessor controller and is primarily intended as a companion product for the AT-AUTO. The CX-AUTO enables selection of any 1-of-8 coaxial outputs and receives selection commands via a serial data interface. When interfaced with an AT-AUTO, the tuner may be configured to associate any of the CX-AUTO's 8 coaxial outputs with an amateur radio band and to automatically command the CX-AUTO to select that particular coaxial output when QSYing to that band.

The AT-AUTO features two RF outputs, a Balanced output, and a coaxial output. The addition of the CX-AUTO effectively expands the AT-AUTO's singular coaxial output to 8 outputs.

While originally intended as an add-on to the AT-AUTO, the CX-AUTO command syntax adheres to the Icom CI-V serial command protocol and is fully PC controllable, without the need for an AT-AUTO. In addition to the CI-V interface, the CX-AUTO also features an RS-422 serial data interface for those applications where the CX-AUTO is to be located well away from the hamshack.

The CX-AUTO is normally powered via a front-panel DC power connector, but DC power may also be supplied via coax.

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A Little About Us

About us icon Kessler Engineering is a privately owned electrical engineering venture providing innovative solutions through design consultation, new product development, and electronics manufacturing. More...

Contact Us!

Contact us icon Use our contact form to request technical support, ask questions, etc.

Please check our FAQ Page to see if we have your question answered there.

Update Your Tuners

Update icon Kessler Engineering will make the latest versions of the tuner's firmware available for download. Support for older firmware versions is available here, too. Download the zip file to install the firmware updates.

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