Kenwood AT-120

Name: Kenwood AT-120
Brand: Kenwood

A small, light HF antenna tuner that Kenwood built by trimming down its popular AT-200. The manual says so outright.

Overview

The AT-120 is an HF antenna tuner, and Kenwood's own documentation says plainly what it is: "a modification of the popular AT-200 antenna tuner," made small and light enough for the ham shack, the field, or a mobile installation. So this isn't a from-scratch design with its own circuit philosophy. It's a proven tuner squeezed into a smaller chassis, and the spec sheet shows where the compromises landed.

The tuner covers five amateur bands spanning 3.5 to 29.7 MHz. The input impedance is 50 ohms, and the universal matching circuit handles loads from 20 to 300 ohms, unbalanced. That means a 50-ohm transceiver on one side, anything from a low dipole to a random wire on the other, and a matching network in between that finds a compromise. Kenwood's manual also notes that the matching circuit acts as a band-pass filter, which helps cut down TVI. In a neighborhood where a stray harmonic means a knock on the door, that counts for something.

Power handling needs some attention. Through power is rated at 120 W max on the 3.5 MHz band, and 150 W on the higher bands. Insertion loss at optimum match is less than 0.5 dB, so you're not paying much in signal to get the match. The AT-120 also has a built-in SWR meter covering the same 3.5 to 29.7 MHz range, with a maximum power rating of 150 W, a measurable range of 1.0:1 to 10:1, and a minimum power requirement of 2 W. That 2 W floor means the meter will still give you a reading from a QRP rig.

The front panel is simple. The band switch selects antenna matching or through operation, and the SWR meter works in both modes. Even in the "through" position, where the antenna connects directly to the transceiver and bypasses the coupler, you can still read your match. The panel meter can be illuminated from an external power source, and Kenwood included a mounting bracket for mobile operation. The whole thing weighs approximately 1.6 kg (3.5 lbs) and measures 152 mm wide by 60 mm high by 159 mm deep. It's a small box.

Around the back, the AT-120 uses UHF-type connectors for both the input and the antenna, both rated at 50 ohms. Grounding is handled by a wing nut and stud. The diecast case and panel, the main tuning knob, the CAL knob, and the band selector knob are all listed as separate service parts in the documentation.

The accessory list in the TS-120S manual shows where the AT-120 sits in Kenwood's lineup. It appears alongside the PS-30 regulated power supply, the MB-100 mobile mount, the YK-88C CW filter, the VFO-120 external VFO, and the SP-120 external speaker. In other words, it was the matching antenna tuner for the TS-120S HF transceiver, a system accessory rather than a standalone flagship.

The documentation does not give production years, an original price, or any contemporary review reception. The AT-120's story in the archives comes almost entirely from Kenwood's own service and owner materials, which are good for specs but thin on market context. Audio press coverage from the period was largely devoted to other Kenwood models. HiFI-Stereo (February 1983, p.52) reviewed the C-1 and M-1 separates, while High-Fidelity (October 1979, p.18) covered the Superex GEM-1 equalizer and a new Kenwood introduction.